A chassis consists of an internal framework that supports a man-made object. It is

analogous to an animal'sskeleton. An example of a chassis is the underpart of a motor

vehicle, consisting of the frame (on which the body is mounted) with the wheels and

machinery.

Examples of use

Vehicles

1950s Jeep FC cowl and chassis for others to convert into finished vehicles

In the case of vehicles, the term chassis means the frame plus the "running gear"

like engine, transmission, driveshaft, differential, and suspension. A body (sometimes

referred to as "coachwork"), which is usually not necessary for integrity of the structure, is

built on the chassis to complete the vehicle. Forcommercial vehicles chassis consists of an

assembly of all the essential parts of a truck (without the body) to be ready for operation on

the road.[1] The design of a pleasure car chassis will be different than one for commercial

vehicles because of the heavier loads and constant work use.[2] Commercial vehicle

manufacturers sell “chassis only”, “cowl and chassis”, as well as "chassis cab" versions that

can be outfitted with specialized bodies. These include motor homes, fire

engines, ambulances, box trucks, etc.

In particular applications, such as school busses, a government agency like National

Highway Traffic Safety Administration (NHTSA) in the U.S. defines the design standards of

chassis and body conversions.[3]

An armoured fighting vehicle's chassis comprises the bottom part of the AFV that includes

the tracks, engine, driver's seat, and crew compartment. This describes the lower hull,

although common usage of might include the upper hull to mean the AFV without the turret. A

chassis serves as basis for platforms on tanks, armored personnel carriers,combat

engineering vehicles, etc.

Frame (vehicle)

From Wikipedia, the free encyclopedia

Cross section of a Chevy Silverado HD 2011 frame

A frame is the main structure of the chassis of a motor vehicle. All other components fasten

to it; a term for this is design is body-on-frameconstruction.

In 1920, every motor vehicle other than a few cars based on motorcycles had a frame. Since

then, nearly all cars have shifted to unit-body construction, while nearly all trucks and buses

still use frames.

Construction

There are three main designs for frame rails. Their cross-sections include:

1. C-shaped

2. Boxed

3. Hat

[edit]C-shape

By far the most common, the C-rail has been used on nearly every type of vehicle at one time

or another. It is made by taking a flat piece of steel (usually ranging in thickness from 1/8" to

3/16") and rolling both sides over to form a c-shaped beam running the length of the vehicle.

[edit]Boxed

Originally, boxed frames were made by welding two matching c-rails together to form a

rectangular tube. Modern techniques, however, use a process similar to making c-rails in that

a piece of steel is bent into four sides and then welded where both ends meet.

In the 1960s, the boxed frames of conventional American cars were spot-welded here and

there down the seam; when turned into NASCAR "stock car" racers, the box was

continuously welded from end to end for extra strength (as was that of the Land-Rover from

its first series).

1956 Chevrolet 1/2-ton frame. Notice hat-shaped crossmember in the background, c-shape

rails and crossmember in center, and a slight arch over the axle.

.

[edit]Hat

Hat frames resemble a "U" and may be either right-side-up or inverted with the open area

facing down. Not commonly used due to weakness and a propensity to rust, however they

can be found on 1936-1954 Chevrolet cars and some Studebakers.

Abandoned for a while, the hat frame gained popularity again when companies started

welding it to the bottom of unibody cars, in effect creating a boxed frame.

[edit]Design Features

While appearing at first glance as a simple hunk of metal, frames encounter great amounts of

stress and are built accordingly. The first issue addressed isbeam height, or the height of the

vertical side of a frame. The taller the frame, the better it is able to resist vertical flex when

force is applied to the top of the frame. This is the reason semi-trucks have taller frame rails

than other vehicles instead of just being thicker.

Another factor considered when engineering a frame is torsional resistance, or the ability to

resist twisting. This, and diamonding (one rail moving backwards or forwards in relation to the

other rail), are countered by crossmembers. While hat-shaped crossmembers are the norm,

these forces are best countered with "K" or "X"-shaped crossmembers.

As looks, ride quality, and handling became more of an issue with consumers, new shapes

were incorporated into frames. The most obvious of these are arches and kick-ups. Instead

of running straight over both axles, arched frames sit roughly level with their axles and curve

up over the axles and then back down on the other side for bumper placement. Kick-ups do

the same thing, but don't curve down on the other side, and are more common on front ends.

On perimeter frames, the areas where the rails connect from front to center and center to

rear are weak compared to regular frames, so that section is boxed in, creating what's known

as torque boxes.

Another feature seen are tapered rails that narrow vertically and/or horizontally in front of a

vehicle's cabin. This is done mainly on trucks to save weight and slightly increase room for

the engine since the front of the vehicle doesn't bear as much of a load as the back.

2007 Toyota Tundra chassis showing an x-shaped crossmember at the back.

The latest design element is frames that use more than one shape in the same frame rail. For

example, the new Toyota Tundra uses a boxed frame in front of the cab, shorter, narrower

rails underneath the cab for ride quality, and regular c-rails under the bed.

[edit]Types

[edit]Ladder Frame

So named for its resemblance to a ladder, the ladder frame is the simplest and oldest of all

designs. It consists merely of two symmetrical rails, or beams, and crossmembers connecting

them. Originally seen on almost all vehicles, the ladder frame was gradually phased out on

cars around the 1940s in favor of perimeter frames and is now seen mainly on trucks.

This design offers good beam resistance because of its continuous rails from front to rear,

but poor resistance to torsion or warping if simple, perpendicular crossmembers are used.

Also, the vehicle's overall height will be higher due to the floor pan sitting above the frame

instead of inside it.

[edit]Backbone tube

Main article: Backbone chassis

Backbone chassis is a type of an automobile construction chassis that is similar to the body-

on-frame design. Instead of a two-dimensional ladder type structure, it consists of a strong

tubular backbone (usually rectangular in cross section) that connects the front and rear

suspension attachment areas. A body is then placed on this structure.

[edit]Perimeter Frame

Similar to a ladder frame, but the middle sections of the frame rails sit outboard of the front

and rear rails just behind the rocker panels/sill panels. This was done to allow for a lower

floor pan, and therefore lower overall vehicle in passenger cars. This was the prevalent

design for cars in the United States, but not in the rest of the world, until the uni-body gained

popularity and is still used on US full frame cars. It allowed for annual model changes

introduced in the 1950s to increase sales, but without costly structural changes.

In addition to a lowered roof, the perimeter frame allows for more comfortable lower seating

positions and offers better safety in the event of a side impact. However, the reason this

design isn't used on all vehicles is that it lacks stiffness, because the transition areas from

front to center and center to rear reduce beam and torsional resistance, hence the use of

torque boxes, and soft suspension settings.

[edit]Superleggera

An Italian term (meaning "super-light") for sports-car construction using a three-dimensional

frame that consists of a cage of narrow tubes that, besides being under the body, run up the

fenders and over the radiator, cowl, and roof, and under the rear window; it resembles a

geodesic structure. The body, which is not stress-bearing, is attached to the outside of the

frame and is often made of aluminium.

[edit]Unibody

Main article: Unibody

By far the most common design in use today, sometimes referred to as a sort of frame.

But the distinction still serves a purpose: if a unibody is damaged in an accident, getting bent

or warped, in effect its frame is too, and the vehicle undrivable. If the body of a body-on-

frame vehicle is similarly damaged, it might be torn in places from the frame, which may still

be straight, in which case the vehicle is simpler and cheaper to repair.

[edit]Sub Frame

Main article: Subframe

The sub frame, or stub frame, is a boxed frame section that attaches to a unibody. Seen

primarily on the front end of cars, it's also sometimes used in the rear. Both the front and rear

are used to attach the suspension to the vehicle and either may contain

the engine and transmission

Basic Engine Parts

The core of the engine is the cylinder, with the piston moving up and down inside the

cylinder. The engine described above has one cylinder. That is typical of most lawn mowers,

but mostcars have more than one cylinder (four, six and eight cylinders are common). In a

multi-cylinder engine, the cylinders usually are arranged in one of three

ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the

following figures.

Different configurations have different advantages and disadvantages in terms of

smoothness, manufacturing cost and shape characteristics. These advantages and

disadvantages make them more suitable for certain vehicles.

Figure 3. V - The cylinders are arranged in two banks set at an angle to one another.

Figure 4. Flat - The cylinders are arranged in two banks on opposite sides of the engine.

Let's look at some key engine parts in more detail.

Spark plug

The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can

occur. The spark must happen at just the right moment for things to work properly.

Valves

The intake and exhaust valves open at the proper time to let in air and fuel and to let out

exhaust. Note that both valves are closed during compression and combustion so that the

combustion chamber is sealed.

Piston

A piston is a cylindrical piece of metal that moves up and down inside the cylinder.

Piston rings

Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of

the cylinder. The rings serve two purposes:

They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking

into the sump during compression and combustion.

They keep oil in the sump from leaking into the combustion area, where it would be

burned and lost.

Most cars that "burn oil" and have to have a quart added every 1,000 miles are burning it

because the engine is old and the rings no longer seal things properly.

Connecting rod

The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its

angle can change as the piston moves and the crankshaft rotates.

Crankshaft

The crankshaft turns the piston's up and down motion into circular motion just like a crank on

a jack-in-the-box does.

Sump

The sump surrounds the crankshaft. It contains some amount of oil, which collects in the

bottom of the sump (the oil pan).

Internal combustion engine cooling

From Wikipedia, the free encyclopedia

Internal combustion engine cooling refers to the cooling of an internal combustion engine,

typically using either air or a liquid.

[edit]Overview

Heat engines generate mechanical power by extracting energy from heat flows, much as

a water wheel extracts mechanical power from a flow of mass falling through a distance.

Engines are inefficient, so more heat energy enters the engine than comes out as

mechanical power; the difference is waste heat which must be removed. Internal combustion

engines remove waste heat through cool intake air, hot exhaust gases, and explicit engine

cooling.

Engines with higher efficiency have more energy leave as mechanical motion and less as

waste heat. Some waste heat is essential: it guides heat through the engine, much as a

water wheel works only if there is some exit velocity (energy) in the waste water to carry it

away and make room for more water. Thus, all heat engines need cooling to operate.

Cooling is also needed because high temperatures damage engine materials and lubricants.

Internal-combustion engines burn fuel hotter than the melting temperature of engine

materials, and hot enough to set fire to lubricants. Engine cooling removes energy fast

enough to keep temperatures low so the engine can survive.

Some high-efficiency engines run without explicit cooling and with only accidental heat loss, a

design called adiabatic. For example, 10,000 mile-per-gallon "cars" for the Shell economy

challenge[1] are insulated, both to transfer as much energy as possible from hot gases to

mechanical motion, and to reduce reheat losses when restarting. Such engines can achieve

high efficiency but compromise power output, duty cycle, engine weight, durability, and

emissions.

[edit]Basic principles

Most internal combustion engines are fluid cooled using either air (a gaseous fluid) or a liquid

coolant run through a heat exchanger (radiator) cooled by air. Marine engines and some

stationary engines have ready access to a large volume of water at a suitable temperature.

The water may be used directly to cool the engine, but often has sediment, which can clog

coolant passages, or chemicals, such as salt, that can chemically damage the engine. Thus,

engine coolant may be run through a heat exchanger that is cooled by the body of water.

Most liquid-cooled engines use a mixture of water and chemicals such as antifreeze and rust

inhibitors. The industry term for the antifreeze mixture is engine coolant. Some antifreezes

use no water at all, instead using a liquid with different properties, such as propylene

glycol or a combination of propylene glycol and ethylene glycol. Most "air-cooled" engines

use some liquid oil cooling, to maintain acceptable temperatures for both critical engine parts

and the oil itself. Most "liquid-cooled" engines use some air cooling, with the intake stroke of

air cooling the combustion chamber. An exception isWankel engines, where some parts of

the combustion chamber are never cooled by intake, requiring extra effort for successful

operation.

There are many demands on a cooling system. One key requirement is that an engine fails if

just one part overheats. Therefore, it is vital that the cooling system keep all parts at suitably

low temperatures. Liquid-cooled engines are able to vary the size of their passageways

through the engine block so that coolant flow may be tailored to the needs of each area.

Locations with either high peak temperatures (narrow islands around the combustion

chamber) or high heat flow (around exhaust ports) may require generous cooling. This

reduces the occurrence of hot spots, which are more difficult to avoid with air cooling. Air-

cooled engines may also vary their cooling capacity by using more closely spaced cooling

fins in that area, but this can make their manufacture difficult and expensive.

Only the fixed parts of the engine, such as the block and head, are cooled directly by the

main coolant system. Moving parts such as the pistons, and to a lesser extent the crank and

rods, must rely on the lubrication oil as a coolant, or to a very limited amount of conduction

into the block and thence the main coolant. High performance engines frequently have

additional oil, beyond the amount needed for lubrication, sprayed upwards onto the bottom of

the piston just for extra cooling. Air-cooled motorcycles often rely heavily on oil-cooling in

addition to air-cooling of the cylinder barrels.

Liquid-cooled engines usually have a circulation pump. The first engines relied on thermo-

syphon cooling alone, where hot coolant left the top of the engine block and passed to the

radiator, where it was cooled before returning to the bottom of the engine. Circulation was

powered by convection alone.

Other demands include cost, weight, reliability, and durability of the cooling system itself.

Conductive heat transfer is proportional to the temperature difference between materials. If

engine metal is at 250 °C and the air is at 20°C, then there is a 230°C temperature difference

for cooling. An air-cooled engine uses all of this difference. In contrast, a liquid-cooled engine

might dump heat from the engine to a liquid, heating the liquid to 135°C (Water's standard

boiling point of 100°C can be exceeded as the cooling system is both pressurised, and uses

a mixture with antifreeze) which is then cooled with 20°C air. In each step, the liquid-cooled

engine has half the temperature difference and so at first appears to need twice the cooling

area.

However, properties of the coolant (water, oil, or air) also affect cooling. As example,

comparing water and oil as coolants, one gram of oil can absorb about 55% of the heat for

the same rise in temperature (called the specific heat capacity). Oil has about 90% the

density of water, so a given volume of oil can absorb only about 50% of the energy of the

same volume of water. The thermal conductivity of water is about 4 times that of oil, which

can aid heat transfer. The viscosity of oil can be ten times greater than water, increasing the

energy required to pump oil for cooling, and reducing the net power output of the engine.

Comparing air and water, air has vastly lower heat capacity per gram and per volume (4000)

and less than a tenth the conductivity, but also much lower viscosity (about 200 times lower:

17.4 × 10−6Pa·s for air vs 8.94 × 10−4 Pa·s for water). Continuing the calculation from two

paragraphs above, air cooling needs ten times of the surface area, therefore the fins, and air

needs 2000 times the flow velocity and thus a recirculating air fan needs ten times the power

of a recirculating water pump. Moving heat from the cylinder to a large surface area for air

cooling can present problems such as difficulties manufacturing the shapes needed for good

heat transfer and the space needed for free flow of a large volume of air. Water boils at about

the same temperature desired for engine cooling. This has the advantage that it absorbs a

great deal of energy with very little rise in temperature (called heat of vaporization), which is

good for keeping things cool, especially for passing one stream of coolant over several hot

objects and achieving uniform temperature. In contrast, passing air over several hot objects

in series warms the air at each step, so the first may be over-cooled and the last under-

cooled. However, once water boils, it is an insulator, leading to a sudden loss of cooling

where steam bubbles form (for more, see heat transfer). Unfortunately, steam may return to

water as it mixes with other coolant, so an engine temperature gauge can indicate an

acceptable temperature even though local temperatures are high enough that damage is

being done.

An engine needs different temperatures. The inlet including the compressor of a turbo and in

the inlet trumpets and the inlet valves need to be as cold as possible. A countercurrent heat

exchange with forced cooling air does the job. The cylinder-walls should not heat up the air

before compression, but also not cool down the gas at the combustion. A compromise is a

wall temperature of 90°C. The viscosity of the oil is optimized for just this temperature. Any

cooling of the exhaust and the turbine of the turbocharger reduces the amount of power

available to the turbine, so the exhaust system is often insulated between engine and

turbocharger to keep the exhaust gases as hot as possible.

The temperature of the cooling air may range from well below freezing to 50°C. Further, while

engines in long-haul boat or rail service may operate at a steady load, road vehicles often

see widely varying and quickly varying load. Thus, the cooling system is designed to vary

cooling so the engine is neither too hot nor too cold. Cooling system regulation includes

adjustable baffles in the air flow (sometimes called 'shutters' and commonly run by a

pneumatic 'shutterstat); a fan which operates either independently of the engine, such as an

electric fan, or which has an adjustable clutch; a thermostatic valve or just 'thermostat' that

can block the coolant flow when too cool. In addition, the motor, coolant, and heat exchanger

have some heat capacity which smooths out temperature increase in short sprints. Some

engine controls shut down an engine or limit it to half throttle if it overheats. Modern

electronic engine controls adjust cooling based on throttle to anticipate a temperature rise,

and limit engine power output to compensate for finite cooling.

Finally, other concerns may dominate cooling system design. As example, air is a relatively

poor coolant, but air cooling systems are simple, and failure rates typically rise as the square

of the number of failure points. Also, cooling capacity is reduced only slightly by small air

coolant leaks. Where reliability is of utmost importance, as in aircraft, it may be a good trade-

off to give up efficiency, durability (interval between engine rebuilds), and quietness in order

to achieve slightly higher reliability — the consequences of a broken airplane engine are so

severe, even a slight increase in reliability is worth giving up other good properties to achieve

it.

Air-cooled and liquid-cooled engines are both used commonly. Each principle has

advantages and disadvantages, and particular applications may favor one over the other. For

example, most cars and trucks use liquid-cooled engines, while many small airplane and low-

cost engines are air-cooled.

[edit]Generalization difficulties

It is difficult to make generalizations about air-cooled and liquid-cooled engines. Air-

cooled Volkswagen kombis are known[who?] for rapid wear in normal use[citation needed] and

sometimes sudden failure when driven in hot weather. Alternatively, air-cooled Deutz diesel

engines are known for reliability even in extreme heat, and are often used in situations where

the engine runs unattended for months at a time.

Similarly, it is usually desirable to minimize the number of heat transfer stages in order to

maximize the temperature difference at each stage. However, Detroit Diesel 2-stroke cycle

engines commonly use oil cooled by water, with the water in turn cooled by air.

The coolant used in many liquid-cooled engines must be renewed periodically, and can

freeze at ordinary temperatures thus causing permanent engine damage. Air-cooled engines

do not require coolant service, and do not suffer engine damage from freezing, two

commonly cited advantages for air-cooled engines. However, coolant based on propylene

glycol is liquid to -55 °C, colder than is encountered by many engines; shrinks slightly when it

crystallizes, thus avoiding engine damage; and has a service life over 10,000 hours,

essentially the lifetime of many engines.

It is usually more difficult to achieve either low emissions or low noise from an air-cooled

engine, two more reasons most road vehicles use liquid-cooled engines. It is also often

difficult to build large air-cooled engines, so nearly all air-cooled engines are under

500 kW (670 hp), whereas large liquid-cooled engines exceed 80 MW (107000 hp) (Wärtsilä-

Sulzer RTA96-C 14-cylinder diesel).

[edit]Air-cooling

Further information: Air cooler

Cars and trucks using direct air cooling (without an intermediate liquid) were built over a long

period from the very beginning and ending with a small and generally unrecognized technical

change. BeforeWorld War II, water-cooled cars and trucks routinely overheated while

climbing mountain roads, creating geysers of boiling cooling water. This was considered

normal, and at the time, most noted mountain roads had auto repair shops to minister to

overheating engines.

ACS (Auto Club Suisse) maintains historical monuments to that era on the Susten

Pass where two radiator refill stations remain (See a picture here). These have instructions

on a cast metal plaque and a spherical bottom watering can hanging next to a water spigot.

The spherical bottom was intended to keep it from being set down and, therefore, be useless

around the house, in spite of which it was stolen, as the picture shows.

During that period, European firms such as Magirus-Deutz built air-cooled diesel trucks,

Porsche built air-cooled farm tractors,[2] and Volkswagen became famous with air-cooled

passenger cars. In the USA, Franklin built air-cooled engines. The Czechoslovakia based

company Tatra is known for their big size air-cooled V8 car engines, Tatra engineer Julius

Mackerle published a book on it. Air-cooled engines are better adapted to extremely cold and

hot environmental weather temperatures, you can see air-cooled engines starting and

running in freezing conditions that stuck water-cooled engines and continue working when

water-cooled ones start producing steam jets.

[edit]Liquid cooling

Today, most engines are liquid-cooled.[3][4][5]

A fully closed IC engine cooling system

Open IC engine cooling system

Semiclosed IC engine cooling system

Liquid cooling is also employed in maritime vehicles (vessels, ...). For vessels, the seawater

itself is mostly used for cooling. In some cases, chemical coolants are also employed (in

closed systems) or they are mixed with seawater cooling.[6][7]

[edit]Transition Away From Air Cooling

The change of air cooling to liquid cooling occurred at the start of World War II when the US

military needed reliable vehicles. The subject of boiling engines was addressed, researched,

and a solution found. Previous radiators and engine blocks were properly designed and

survived durability tests, but used water pumps with a leaky graphite-lubricated "rope" seal

(gland) on the pump shaft. The seal was inherited from steam engines, where water loss is

accepted, since steam engines already expend large volumes of water. Because the pump

seal leaked mainly when the pump was running and the engine was hot, the water loss

evaporated inconspicuously, leaving at best a small rusty trace when the engine stopped and

cooled, thereby not revealing significant water loss. Automobile radiators (or heat

exchangers) have an outlet that feeds cooled water to the engine and the engine has an

outlet that feeds heated water to the top of the radiator. Water circulation is aided by a rotary

pump that has only a slight effect, having to work over such a wide range of speeds that its

impeller has only a minimal effect as a pump. While running, the leaking pump seal drained

cooling water to a level where the pump could no longer return water to the top of the

radiator, so water circulation ceased and water in the engine boiled. However, since water

loss led to overheat and further water loss from boil-over, the original water loss was hidden.

After isolating the pump problem, cars and trucks built for the war effort (no civilian cars were

built during that time) were equipped with carbon-seal water pumps that did not leak and

caused no more geysers. Meanwhile, air cooling advanced in memory of boiling engines...

even though boil-over was no longer a common problem. Air-cooled engines became popular

throughout Europe. After the war, Volkswagen advertised in the USA as not boiling over,

even though new water-cooled cars no longer boiled over, but these cars sold well, and

without question. But as air quality awareness rose in the 1960s, and laws governing exhaust

emissions were passed, unleaded gas replaced leaded gas and leaner fuel mixtures became

the norm. These reductions in the cooling effects of both the lead and the formerly rich fuel

mixture, led to overheating in the air-cooled engines.[citation needed] Valve failures and other

engine damage was the result.[citation needed] Volkswagen responded by abandoning their (flat)

horizontally opposed air-cooled engines,[citation needed] while Subaru took a different course and

chose liquid-cooling for their (flat) engines.

Today practically no air-cooled automotive engines are built, air cooling being fraught with

manufacturing expense and maintenance problems. Motorcycles had an additional problem

in that a water leak presented a greater threat to reliability, their engines having small cooling

water volume, so they were loath to change; today most larger motorcycles are water-cooled

with many relying on convection circulation with no pump.

For the forty years following the first flight of the Wright brothers, airplanes used internal combustion engines to turnpropellers to generate thrust. Today, most general aviation or private airplanes are still powered by propellers and internal combustion engines, much like your automobile engine. We will discuss the fundamentals of the internal combustion engine using the Wright brothers' 1903 engine, shown in the figure, as an example. The brothers' design is very simple by today's standards, so it is a good engine for students to study and learn the fundamentals of engines and their operation. On this page we present a computer drawing of the lubrication system of the Wright brothers' 1903 aircraft engine.

Mechanical Operation

The figure at the top shows the major components of the lubrication system on the Wright 1903 engine. In any internal combustion engine, fuel and oxygen are combined in a combustion process to produce the power to turn the crankshaft of the engine. The combustion generates high pressure exhaust gas which exerts a force on the face of a piston. The piston moves inside a cylinder and is connected to the crankshaft by a rod which transmits the power. There are many moving parts is this power train as shown in this computer animation:

The job of the lubrication system is to distribute oil to the moving parts to reduce friction between surfaces which rub against each other.

The lubrication system used by the Wright brothers is quite simple. An oil pump is located on the bottom of the engine, at the left of the figure. The pump is driven by a worm gear off the main exhaust valve cam shaft. The oil is pumped to the top of the engine, at the right, inside a feed line. Small holes in the feed line allow the oil to drip inside the crankcase. In the figure, we have removed the fuel system and peeled back the covering of the crankcase to see inside. The oil drips onto the pistons as they move in the cylinders, lubricating the surface between the piston and cylinder. The oil then runs down inside the crankcase to the main bearings holding the crankshaft. Oil is picked up and splashed onto the bearings to lubricate these surfaces. Along the outside of the bottom of the crankcase is a collection tube which gathers up the used oil andreturns it to the oil pump to be circulated again. Notice that the brothers did not lubricate the valves and rocker assembly for the combustion chambers.

Difference between a turbocharger and a supercharger on a cars engine

Let's start with the similarities. Both turbochargers and superchargers are called forced

induction systems. They compress the air flowing into the engine (see How Car Engines

Work for a description of airflow in a normal engine). The advantage of compressing the air is

that it lets the engine stuff more air into a cylinder. More air means that more fuel can be

stuffed in, too, so you get more power from each explosion in each cylinder. A

turbo/supercharged engine produces more power overall than the same engine without the

charging.

The typical boost provided by either a turbocharger or a supercharger is 6 to 8 pounds per

square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see

that you are getting about 50-percent more air into the engine. Therefore, you would expect

to get 50-percent more power. It's not perfectly efficient, though, so you might get a 30-

percent to 40-percent improvement instead.

The key difference between a turbocharger and a supercharger is its power supply.

Something has to supply the power to run the air compressor. In a supercharger, there is

a belt that connects directly to the engine. It gets its power the same way that the water

pump or alternator does. A turbocharger, on the other hand, gets its power from the exhaust

stream. The exhaust runs through a turbine, which in turn spins the compressor (see How

Gas Turbine Engines Work for details).

There are tradeoffs in both systems. In theory, a turbocharger is more efficient because it is

using the "wasted" energy in the exhaust stream for its power source. On the other hand, a

turbocharger causes some amount of back pressure in the exhaust system and tends to

provide less boost until the engine is running at higher RPMs. Superchargers are easier to

install but tend to be more expensive.

Emission Standards

Emission standards are requirements that set specific limits to the amount

of pollutants that can be released into the environment. Many emissions standards

focus on regulating pollutants released by automobiles (motor cars) and other

powered vehicles but they can also regulate emissions from industry, power plants,

small equipment such as lawn mowers and diesel generators. Frequent policy

alternatives to emissions standards are technology standards (which mandate

Standards generally regulate the emissions of nitrogen oxides (NOx), sulfur

oxides, particulate matter (PM) or soot,carbon monoxide (CO), or

volatile hydrocarbons (see carbon dioxide equivalent).

Contents

  [hide] 

1   Vehicle Emission performance standard

2   Americas

o 2.1   USA

3   Europe

o 3.1   European Union

o 3.2   UK

o 3.3   Germany

4   Asia

o 4.1   China

o 4.2   Hong Kong

o 4.3   India

4.3.1   Background

4.3.2   Trucks and Buses

4.3.3   Light duty diesel vehicles

4.3.4   Light duty gasoline vehicles

4.3.4.1   4-wheel vehicles

4.3.4.2   3- and 2-wheel vehicles

4.3.5   Overview of the emission norms in India by CDR

o 4.4   Japan

5   See also

6   References

7   External links

o 7.1   EU

[edit]Vehicle Emission performance standard

This section needs additional citations for verification. Please help improve

this article by adding citations to reliable sources. Unsourced material may

be challenged and removed. (January 2009)

An emission performance standard is a limit that sets thresholds above which a

different type of emission control technology might be needed. While emission

performance standards have been used to dictate limits for

conventional pollutants such as oxides of nitrogen and oxides of sulfur (NOx and

SOx),[1] this regulatory technique may be used to regulate greenhouse gasses,

particularlycarbon dioxide (CO2). In the US, this is given in pounds of carbon dioxide

per megawatt-hour (lbs. CO2/MWhr), and kilograms CO2/MWhr elsewhere in the

world...

[edit]Americas

This section requires expansion.

[edit]USAMain article: United States emission standards

In the United States, emissions standards are managed by the Environmental

Protection Agency (EPA). The state of California has special dispensation to

promulgate more stringent vehicle emissions standards, and other states may choose

to follow either the national or California standards.

California's emissions standards are set by the California Air Resources Board, known

locally by its acronym "CARB". Given that California's automotive market is one of the

largest in the world, CARB wields enormous influence over the emissions

requirements that major automakers must meet if they wish to sell into that market. In

addition, several other U.S. states also choose to follow the CARB standards, so their

rulemaking has broader implications within the U.S. How Stuff Works: CARB lists 16

other states adopting CARB rules as of mid 2009. CARB's policies have also

influenced EU emissions standards.

Federal (National) "Tier 1" regulations went into effect starting in 1994, and "Tier 2"

standards are being phased in from 2004 to 2009. Automobiles and light

trucks (SUVs, pickup trucks, and minivans) are treated differently under certain

standards.

California is attempting to regulate greenhouse gas emissions from automobiles, but

faces a court challenge from the federal government. The states are also attempting

to compel the federal EPA to regulate greenhouse gas emissions, which as of 2007 it

has declined to do. On May 19, 2009 news reports indicate that the Federal EPA will

largely adopt California's standards on greenhouse gas emissions.

California and several other western states have passed bills requiring performance-

based regulation of greenhouse gases from electricity generation.

In an effort to decrease emissions from heavy-duty diesel engines faster,

the California Air Resources Board's Carl Moyer Program funds upgrades that are in

advance of regulations.

The EPA has separate regulations for small engines, such as groundskeeping

equipment. The states must also promulgate miscellaneous emissions regulations in

order to comply with the National Ambient Air Quality Standards.

Europe

European UnionMain article: European emission standards

The European Union has its own set of emissions standards that all new vehicles

must meet. Currently, standards are set for all road vehicles, trains, barges and

'nonroad mobile machinery' (such as tractors). No standards apply to seagoing ships

or airplanes. The emissions standards change based on the test cycle used: ECE R49

(old) and ESC (European Steady Cycle, since 2000).

Currently there are no standards for CO2 emissions. The European Parliament has

suggested introducing mandatory CO2 emission standards[2] to replace current

voluntary commitments by the auto manufacturers (see ACEA agreement) and

labeling. In late 2005, the European Commission started working on a proposal for a

new law to limit CO2 emissions from cars.[3] The European Commission has received

support of the European Parliament for its proposal to promote a broad market

introduction of clean and energy efficient vehicles through public procurement.[4]

The EU is to introduce Euro 4 effective January 1, 2008, Euro 5 effective January 1,

2010 and Euro 6 effective January 1, 2014. These dates have been postponed for two

years to give oil refineries the opportunity to modernize their plants.

UK

The British Parliament proposed legislation regulating CO2 emissions from electricity

generation via emission performance standards.[5] This bill was even more stringent

than that of the western American states in that it limited production to the equivalent

of 400 kg CO2/MWh, which would effectively preclude the construction of any

traditional coal-fired power plants.

Germany

According to the German federal automotive office 37.3 % (15.4 million) cars in

Germany (total car population 41.3 million) conform to the Euro 4 standard from Jan

2009.

Due to rapidly expanding wealth and prosperity, the number of coal power plants and

cars on China's roads is rapidly growing, creating an ongoing pollution problem. China

enacted its first emissions controls on automobiles in 2000, equivalent to Euro I

standards. China's State Environmental Protection Administration (SEPA) upgraded

emission controls again on July 1, 2004 to the Euro II standard.[6] More stringent

emission standard, National Standard III, equivalent to Euro III standards, went into

effect on July 1, 2007.[7] Plans are for Euro IV standards to take effect in 2010. Beijing

introduced the Euro IV standard in advance on January 1, 2008, became the first city

in mainland China to adopt this standard.[8]

Hong Kong

From Jan 1, 2006, all new passenger cars with spark-ignition engines in Hong

Kong must meet either Euro IV petrol standard, Japanese Heisei 17 standard or US

EPA Tier 2 Bin 5 standard. For new passenger cars with compression-ignition

engines, they must meet US EPA Tier 2 Bin 5 standard.

Background

The first Indian emission regulations were idle emission limits which became effective

in 1989. These idle emission regulations were soon replaced by mass emission limits

for both petrol (1991) and diesel (1992) vehicles, which were gradually tightened

during the 1990s. Since the year 2000, India started adopting European emission and

fuel regulations for four-wheeled light-duty and for heavy-dc. Indian own emission

regulations still apply to two- and three-wheeled vehicles.

Current requirement is that all transport vehicles carry a fitness certificate that is

renewed each year after the first two years of new vehicle registration.

On October 6, 2003, the National Auto Fuel Policy has been announced, which

envisages a phased program for introducing Euro 2 - 4 emission and fuel regulations

by 2010. The implementation schedule of EU emission standards in India is

summarized in Table 1.[9]

Table 1: Indian Emission Standards (4-Wheel Vehicles)

Standard Reference Date Region

India 2000 Euro 1 2000 Nationwide

Bharat Stage II Euro 2

2001 NCR*, Mumbai, Kolkata, Chennai

2003.04 NCR*, 12 Cities†

2005.04 Nationwide

Bharat Stage III Euro 3

2005.04 NCR*, 12 Cities†

2010.04 Nationwide

Bharat Stage IV Euro 4 2010.04 NCR*, 12 Cities†

* National Capital Region (Delhi)

† Mumbai, Kolkata, Chennai, Bengaluru, Hyderabad, Ahmedabad, Pune, Surat, Kanpur, Lucknow, Sholapur, and Agra

The above standards apply to all new 4-wheel vehicles sold and registered in the

respective regions. In addition, the National Auto Fuel Policy introduces certain

emission requirements for interstate buses with routes originating or terminating in

Delhi or the other 10 cities.

For 2-and 3-wheelers, Bharat Stage II (Euro 2) will be applicable from April 1, 2005

and Stage III (Euro 3) standards would come in force preferably from April 1, 2008,

but not later than April 1, 2010.[10]

[edit]Trucks and Buses

Emission standards for new heavy-duty diesel engines—applicable to vehicles of GVW > 3,500 kg—

are listed in Table 1. Emissions are tested over the ECE R49 13-mode test (through the Euro II stage)

Table 2 Emission Standards for Diesel Truck and Bus Engines,

g/kWh

Year Reference CO HC NOx PM

1992 - 17.3-32.6 2.7-3.7 - -

1996 - 11.20 2.40 14.4 -

2000 Euro I 4.5 1.1 8.0 0.36*

2005† Euro II 4.0 1.1 7.0 0.15

2010† Euro III 2.1 0.66 5.0 0.10

* 0.612 for engines below 85 kW

† earlier introduction in selected regions, see Table 1

More details on Euro I-III regulations can be found in the EU heavy-duty engine

standards page.

[edit]Light duty diesel vehicles

Emission standards for light-duty diesel vehicles (GVW ≤ 3,500 kg) are summarized in Table 3.

Ranges of emission limits refer to different classes (by reference mass) of light commercial vehicles;

compare the EU light-duty vehicle emission standards page for details on the Euro 1 and later

standards. The lowest limit in each range applies to passenger cars (GVW ≤ 2,500 kg; up to 6 seats).

Table 3 Emission Standards for Light-Duty Diesel Vehicles, g/km

Year Reference CO HC HC+NOx PM

1992 - 17.3-32.6 2.7-3.7 - -

1996 - 5.0-9.0 - 2.0-4.0 -

2000 Euro 1 2.72-6.90 - 0.97-1.70 0.14-0.25

2005† Euro 2 1.0-1.5 - 0.7-1.2 0.08-0.17

The test cycle has been the ECE + EUDC for low power vehicles (with maximum

speed limited to 90 km/h). Before 2000, emissions were measured over an Indian test

cycle.

Engines for use in light-duty vehicles can be also emission tested using an engine dynamometer. The

respective emission standards are listed in Table 4.

Table 4 Emission Standards for Light-Duty Diesel Engines, g/kWh

Year Reference CO HC NOx PM

1992 - 14.0 3.5 18.0 -

1996 - 11.20 2.40 14.4 -

2000 Euro I 4.5 1.1 8.0 0.36*

2005† Euro II 4.0 1.1 7.0 0.15

* 0.612 for engines below 85 kW

† earlier introduction in selected regions, see Table 1

[edit]Light duty gasoline vehicles

[edit]4-wheel vehicles

Emissions standards for gasoline vehicles (GVW ≤ 3,500 kg) are summarized in Table 5. Ranges of

emission limits refer to different classes of light commercial vehicles (compare the EU light-duty

vehicle emission standards page). The lowest limit in each range applies to passenger cars (GVW ≤

2,500 kg; up to 6 seats).

Table 5 Emission Standards for Gasoline Vehicles (GVW ≤ 3,500 kg), g/km

Year Reference CO HC HC+NOx

1991 - 14.3-27.1 2.0-2.9 -

1996 - 8.68-12.4 - 3.00-4.36

1998* - 4.34-6.20 - 1.50-2.18

2000 Euro 1 2.72-6.90 - 0.97-1.70

2005† Euro 2 2.2-5.0 - 0.5-0.7

* for catalytic converter fitted vehicles

† earlier introduction in selected regions, see Table 1

Gasoline vehicles must also meet an evaporative (SHED) limit of 2 g/test (effective

2000).

[edit]3- and 2-wheel vehicles

Emission standards for 3- and 2-wheel gasoline vehicles are listed in the following

tables.[11]

Table 6 Emission Standards for 3-Wheel Gasoline Vehicles, g/km

Year CO HC HC+NOx

1991 12-30 8-12 -

1996 6.75 - 5.40

2000 4.00 - 2.00

2005 (BS II) 2.25 - 2.00

Table 7 Emission Standards for 2-Wheel Gasoline Vehicles, g/km

Year CO HC HC+NOx

1991 12-30 8-12 -

1996 5.50 - 3.60 4.60

[edit]Overview of the emission norms in India by CDR

1991 - Idle CO Limits for Gasoline Vehicles and Free Acceleration Smoke for

Diesel Vehicles, Mass Emission Norms for Gasoline Vehicles.

1992 - Mass Emission Norms for Diesel Vehicles.

1996 - Revision of Mass Emission Norms for Gasoline and Diesel Vehicles,

mandatory fitment of Catalytic Converter for Cars in Metros on Unleaded Gasoline.

1998 - Cold Start Norms Introduced .

2000 - India 2000 (Eq. to Euro I) Norms, Modified IDC (Indian Driving Cycle),

Bharat Stage II Norms for Delhi.

2001 - Bharat Stage II (Eq. to Euro II) Norms for All Metros, Emission Norms for

CNG & LPG Vehicles.

2003 - Bharat Stage II (Eq. to Euro II) Norms for 11 major cities.

2005 - From 1 April Bharat Stage III (Eq. to Euro III) Norms for 11 major cities.

2010 - Bharat Stage III Emission Norms for 4-wheelers for entire country

whereas Bharat Stage - IV (Eq. to Euro IV) for 13 major cities. Bharat Stage IV

also has norms on OBD (similar to Euro III but diluted)

[edit]Japan

Background

In 1973 the first installment of four sets of new emissions standards were introduced.

Interim standards were introduced on January 1, 1975 and again for 1976. The final

set of standards were introduced for 1978.[12] While the standards were introduced

they were not made immediately mandatory, instead tax breaks were offered for cars

which passed them.[13] The standards were based on those adopted by the original US

Clean Air Act of 1970, but the test cycle included more slow city driving to correctly

reflect the Japanese situation.[14] The 1978 limits for mean emissions during a "Hot

Start Test" of CO, hydrocarbons, and NOx were 2.1 grams per kilometre (0.00 g/mi) of

CO, .25 grams per kilometre (0.00 g/mi) of HC, and .25 grams per kilometre

(0.00 g/mi) of NOx respectively.[14]Maximum limits are 2.7 grams per kilometre

(0.00 g/mi) of CO, .39 grams per kilometre (0.00 g/mi) of HC, and .48 grams per

kilometre (0.00 g/mi) of NOx. The "10 - 15 Mode Hot Cycle" test, used to determine

individual fuel economy ratings and emissions observed from the vehicle being tested,

use a specific testing regime. [15][16][17]

In 1992, to cope with NOx pollution problems from existing vehicle fleets in highly

populated metropolitan areas, the Ministry of the Environment adopted the “Law

Concerning Special Measures to Reduce the Total Amount of Nitrogen Oxides

Emitted from Motor Vehicles in Specified Areas”, called in short The Motor Vehicle

NOx Law. The regulation designated a total of 196 communities in the Tokyo,

Saitama, Kanagawa, Osaka and Hyogo Prefectures as areas with significant air

pollution due to nitrogen oxides emitted from motor vehicles. Under the Law, several

measures had to be taken to control NOx from in-use vehicles, including enforcing

emission standards for specified vehicle categories.

The regulation was amended in June 2001 to tighten the existing NOx requirements

and to add PM control provisions. The amended rule is called the “Law Concerning

Special Measures to Reduce the Total Amount of Nitrogen Oxides and Particulate

Matter Emitted from Motor Vehicles in Specified Areas”, or in short the Automotive

NOx and PM Law.

Emission Standards

The NOx and PM Law introduces emission standards for specified categories of in-

use highway vehicles including commercial goods (cargo) vehicles such as trucks and

vans, buses, and special purpose motor vehicles, irrespective of the fuel type. The

regulation also applies to diesel powered passenger cars (but not to gasoline cars).

In-use vehicles in the specified categories must meet 1997/98 emission standards for

the respective new vehicle type (in the case of heavy duty engines NOx = 4.5 g/kWh,

PM = 0.25 g/kWh). In other words, the 1997/98 new vehicle standards are

retroactively applied to older vehicles already on the road. Vehicle owners have two

methods to comply:

1. Replace old vehicles with newer, cleaner models

2. Retrofit old vehicles with approved NOx and PM control devices

Vehicles have a grace period, between 9 and 12 years from the initial registration, to

comply. The grace period depends on the vehicle type, as follows:

Light commercial vehicles (GVW ≤ 2500 kg): 8 years

Heavy commercial vehicles (GVW > 2500 kg): 9 years

Micro buses (11-29 seats): 10 years

Large buses (≥ 30 seats): 12 years

Special vehicles (based on a cargo truck or bus): 10 years

Diesel passenger cars: 9 years

Furthermore, the regulation allows fulfillment of its requirements to be postponed by

an additional 0.5-2.5 years, depending on the age of the vehicle. This delay was

introduced in part to harmonize the NOx and PM Law with the Tokyo diesel retrofit

program.

The NOx and PM Law is enforced in connection with Japanese vehicle inspection

program, where non-complying vehicles cannot undergo the inspection in the

designated areas. This, in turn, may trigger an injunction on the vehicle operation

under the Road Transport Vehicle Law.

Vehicle emissions control is the study and practice of reducing the motor vehicle

emissions -- emissions produced by motor vehicles, especially internal combustion

engines.

Emissions of many air pollutants have been shown to have variety of negative

effects on public health and the natural environment. Emissions that are principal

pollutants of concern include:

Hydrocarbons  - A class of burned or partially burned fuel, hydrocarbons

are toxins. Hydrocarbons are a major contributor to smog, which can be a major

problem in urban areas. Prolonged exposure to hydrocarbons contributes

to asthma, liver disease, , lung disease, and cancer. Regulations governing

hydrocarbons vary according to type of engine and jurisdiction; in some cases,

"non-methane hydrocarbons" are regulated, while in other cases, "total

hydrocarbons" are regulated. Technology for one application (to meet a non-

methane hydrocarbon standard) may not be suitable for use in an application that

has to meet a total hydrocarbon standard. Methane is not directly toxic, but is more

difficult to break down in a catalytic converter, so in effect a "non-methane

hydrocarbon" regulation can be considered easier to meet. Since methane is

a greenhouse gas, interest is rising in how to eliminate emissions of it.

Carbon monoxide  (CO) - A product of incomplete combustion, carbon monoxide

reduces the blood's ability to carry oxygen; overexposure (carbon monoxide

poisoning) may be fatal. Carbon Monoxide poisoning is a major killer.

Nitrogen oxides  (NOx) - Generated when nitrogen in the air reacts with oxygen

at the high temperature and pressure inside the engine. NOx is a precursor to

smog and acid rain. NOx is a mixture of NO, N2O, and NO2. NO2 is extremely

reactive. It destroys resistance to respiratory infection. NOx production is increased

when an engine runs at its most efficient (i.e. hottest) part of the cycle.

Particulate matter  – Soot or smoke made up of particles in the micrometre size

range: Particulate matter causes negative health effects, including but not limited

to respiratory disease and cancer.

Sulfur oxide  (SOx) - A general term for oxides of sulfur, which are emitted from

motor vehicles burning fuel containing sulfur. Reducing the level of fuel sulfur

reduces the level of Sulfur oxide emitted from the tailpipe. Refineries generally fight

requirements to do this because of the increased costs to them, ignoring the

increased costs to society as a whole.

Volatile organic compounds  (VOCs) - Organic compounds which typically have

a boiling point less than or equal to 250 °C; for

example chlorofluorocarbons (CFCs) and formaldehyde. Volatile organic

compounds are a subsection of Hydrocarbons that are mentioned separately

because of their dangers to public health.

History

Throughout the 1950s and 1960s, various federal, state and local governments in

the United States conducted studies into the numerous sources of air pollution. These

studies ultimately attributed a significant portion of air pollution to the automobile, and

concluded air pollution is not bounded by local political boundaries. At that time, such

minimal emission control regulations as existed in the U.S. were promulgated at the

municipal or, occasionally, the state level. The ineffective local regulations were

gradually supplanted by more comprehensive state and federal regulations. By 1967

theState of California created the California Air Resources Board, and in 1970, the

federal United States Environmental Protection Agency was established. Both

agencies, as well as other state agencies, now create and enforce emission

regulations for automobiles in the United States. Similar agencies and regulations

were contemporaneously developed and implemented in Canada, Western

Europe,Australia, and Japan.

The first effort at controlling pollution from automobiles was the PCV (positive

crankcase ventilation) system. This draws crankcase fumes heavy in unburned

hydrocarbons — a precursor tophotochemical smog — into the engine's intake tract

so they are burned rather than released unburned from the crankcase into the

atmosphere. Positive crankcase ventilation was first installed on a widespread basis

by law on all new 1961-model cars first sold in California. The following year, New

York required it. By 1964, most new cars sold in the U.S. were so equipped, and PCV

quickly became standard equipment on all vehicles worldwide.[1]

The first legislated exhaust (tailpipe) emission standards were promulgated by the

State of California for 1966 model year for cars sold in that state, followed by the

United States as a whole in model year 1968. The standards were progressively

tightened year by year, as mandated by the EPA.

By the 1974 model year, the emission standards had tightened such that the de-

tuning techniques used to meet them were seriously reducing engine efficiency and

thus increasing fuel usage. The new emission standards for 1975 model year, as well

as the increase in fuel usage, forced the invention of the catalytic converter for after-

treatment of the exhaust gas. This was not possible with existingleaded gasoline,

because the lead residue contaminated the platinum catalyst. In 1972, General

Motors proposed to the American Petroleum Institute the elimination of leaded fuels

for 1975 and later model year cars. The production and distribution of unleaded fuel

was a major challenge, but it was completed successfully in time for the 1975 model

year cars. All modern cars are now equipped with catalytic converters and leaded fuel

is nearly impossible to buy in most First World countries.

[edit]Regulatory agencies

The agencies charged with regulating exhaust emissions vary from jurisdiction to

jurisdiction, even in the same country. For example, in the United States, overall

responsibility belongs to the EPA, but due to special requirements of the State of

California, emissions in California are regulated by the Air Resources Board. In Texas,

the Texas Railroad Commission is responsible for regulating emissions from LPG-

fueled rich burn engines (but not gasoline-fueled rich burn engines).

[edit]North America

California Air Resources Board  - California, United States (most sources)

Environment Canada  - Canada (most sources)

Environmental Protection Agency  - United States (most sources)

Texas Railroad Commission  - Texas, United States (LPG-fueled engines only)

Transport Canada  - Canada (trains and ships)

[edit]Europe

Ultimately, the European Union has control over regulation of emissions in EU

member states; however, many member states have their own government bodies to

enforce and implement these regulations in their respective countries. In short, the EU

forms the policy (by setting limits such as the European emission standard) and the

member states decide how to best implement it in their own country.

[edit]United Kingdom

In the United Kingdom, matters concerning environmental policy are what is known as

"devolved powers" which means, each of the constituent countries deals with it

separately through their own government bodies set up to deal with environmental

issues in their respective country:

Environment Agency  - England and Wales

Scottish Environment Protection Agency  (SEPA) - Scotland

Department of the Environment  - Northern Ireland

However, many UK-wide policies are handled by the Department of the Environment

Food and Rural Affairs (DEFRA) and they are still subject to EU regulations.

[edit]Emissions control

Engine efficiency has been steadily improved with improved engine design, more

precise ignition timing and electronic ignition, more precise fuel metering,

and computerized engine management.

Advances in engine and vehicle technology continually reduce the toxicity of exhaust

leaving the engine, but these alone have generally been proved insufficient to meet

emissions goals. Therefore, technologies to detoxify the exhaust are an essential part

of emissions control.

[edit]Air injectionMain article: Secondary air injection

One of the first-developed exhaust emission control systems is secondary air

injection. Originally, this system was used to inject air into the engine's exhaust ports

to provide oxygen so unburned and partially-burned hydrocarbons in the exhaust

would finish burning. Air injection is now used to support the catalytic converter's

oxidation reaction, and to reduce emissions when an engine is started from cold. After

a cold start, an engine needs a fuel-air mixture richer than what it needs at operating

temperature, and the catalytic converter does not function efficiently until it has

reached its own operating temperature. The air injected upstream of the converter

supports combustion in the exhaust headpipe, which speeds catalyst warmup and

reduces the amount of unburned hydrocarbon emitted from the tailpipe.

Air Injection is a secondary technology, used in support of the main technologies on

some engines.

[edit]Exhaust gas recirculationMain article: Exhaust gas recirculation

In the United States and Canada, many engines in 1973 and newer vehicles (1972

and newer in California) have a system that routes a metered amount of exhaust into

the intake tract under particular operating conditions. Exhaust neither burns nor

supports combustion, so it dilutes the air/fuel charge to reduce peak combustion

chamber temperatures. This, in turn, reduces the formation of NOx.

[edit]Catalytic converterMain article: Catalytic converter

The catalytic converter is a device placed in the exhaust pipe, which converts

hydrocarbons, carbon monoxide, and NOx into less harmful gases by using a

combination of platinum, palladium and rhodium as catalysts.

There are two types of catalytic converter, a two-way and a three-way converter. Two-

way converters were common until the 1980s, when three-way converters replaced

them on most automobile engines. See the catalytic converter article for further

details.

[edit]Evaporative emissions control

"EVAP" redirects here. EVAP may also refer to Evaporation.

Evaporative emissions are the result of gasoline vapors escaping from the vehicle's

fuel system. Since 1971, all U.S. vehicles have had fully sealed fuel systems that do

not vent directly to the atmosphere; mandates for systems of this type appeared

contemporaneously in other jurisdictions. In a typical system, vapors from the fuel

tank and carburetor bowl vent (on carbureted vehicles) are ducted to canisters

containing activated carbon. The vapors are adsorbed within the canister, and during

certain engine operational modes fresh air is drawn through the canister, pulling the

vapor into the engine,where it burns.

[edit]Emission testing

In 1966, the first emission test cycle was enacted in the State of California measuring

tailpipe emissions in PPM (parts per million).

Some cities are also using a technology developed by Dr. Donald Stedman of

the University of Denver, which uses lasers to detect emissions while vehicles pass by

on public roads, thus eliminating the need for owners to go to a test center. Stedman's

laser detection of exhaust gases is commonly used in metropolitan areas.[2]

[edit]Use of emission test data

Emission test results from individual vehicles are in many cases compiled to evaluate

the emissions performance of various classes of vehicles, the efficacy of the testing

program and of various other emission-related regulations (such as changes to fuel

formulations) and to model the effects of auto emissions on public health and the

environment. For example, the Environmental Working Groupused California ASM

emissions data to create an "Auto Asthma Index" that rates vehicle models according

to emissions of hydrocarbons and nitrogen oxides, chemical precursors

to photochemical smog.

Catalytic convertor

A catalytic converter (colloquially, "cat" or "catcon") is a device used to convert

toxic exhaust emissions from an internal combustion engine into non-toxic

substances. Inside a catalytic converter, a catalyst stimulates a chemical reaction in

which noxious byproducts of combustion are converted to less toxic substances by

dint of catalysed chemical reactions. The specific reactions vary with the type of

catalyst installed. Most present-day vehicles that run ongasoline are fitted with a

"three way" converter, so named because it converts the three main pollutants in

automobile exhaust: an oxidising reaction convertscarbon monoxide (CO)

and unburned hydrocarbons (HC), and a reduction reaction converts oxides of

nitrogen (NOx) to produce carbon dioxide (CO2), nitrogen(N2), and water (H2O).[1]

The first widespread introduction of catalytic converters was in the United

States market, where 1975 model year automobiles were so equipped to comply with

tightening U.S. Environmental Protection Agency regulations on automobile exhaust

emissions. The catalytic converters fitted were two-way models, combining carbon

monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2)

and water (H2O). Two-way catalytic converters of this type are now considered

obsolete except on lean burn engines.[citation needed] Since most vehicles at the time

used carburetors that provided a relatively richair-fuel ratio, oxygen (O2) levels in the

exhaust stream were in general insufficient for the catalytic reaction to occur.

Therefore, most such engines were also equipped with secondary air

injection systems to induct air into the exhaust stream to allow the catalyst to function.

Catalytic converters are still most commonly used on automobile exhaust systems,

but are also used on generator sets, forklifts, mining

equipment, trucks,buses, locomotives, airplanes and other engine fitted devices. This

is usually in response to government regulation, either through direct environmental

regulation or through Health and Safety regulations.

Construction

Metal-core converter

Ceramic-core converter

The catalytic converter consists of several components:

1. The catalyst core, or substrate. For automotive catalytic converters, the core is

usually a ceramic monolith with a honeycomb structure. Metallic foil monoliths

made of FeCrAl are used in some applications. This is partially a cost issue.

Ceramic cores are inexpensive when manufactured in large quantities. Metallic

cores are less expensive to build in small production runs. Either material is

designed to provide a high surface area to support the catalyst washcoat, and

therefore is often called a "catalyst support".[citation needed] The cordierite ceramic

substrate used in most catalytic converters was invented by Rodney

Bagley, Irwin Lachman and Ronald Lewis at Corning Glass, for which they

were inducted into the National Inventors Hall of Fame in 2002.[citation needed]

2. The washcoat. A washcoat is a carrier for the catalytic materials and is used to

disperse the materials over a high surface area. Aluminum oxide,Titanium

dioxide, Silicon dioxide, or a mixture of silica and alumina can be used. The

catalytic materials are suspended in the washcoat prior to applying to the core.

Washcoat materials are selected to form a rough, irregular surface, which

greatly increases the surface area compared to the smooth surface of the bare

substrate. This maximizes the catalytically active surface available to react with

the engine exhaust.

3. The catalyst itself is most often a precious metal. Platinum is the most active

catalyst and is widely used, but is not suitable for all applications because of

unwanted additional reactions[vague] and high cost. Palladium and rhodium are

two other precious metals used. Rhodium is used as areduction catalyst,

palladium is used as an oxidation catalysts, and platinum is used both for

reduction and oxidation. Cerium, iron, manganese andnickel are also used,

although each has its own limitations. Nickel is not legal for use in the

European Union (because of its reaction with carbon monoxide into nickel

tetracarbonyl). Copper can be used everywhere except North America,[clarification

needed] where its use is illegal because of the formation of dioxin.

[edit]Types

[edit]Two-way

A two-way (or "oxidation") catalytic converter has two simultaneous tasks:

1. Oxidation  of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2

2. Oxidation of hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide

and water: CxH2x+2 + [(3x+1)/2] O2 → xCO2 + (x+1) H2O (a combustion reaction)

This type of catalytic converter is widely used on diesel engines to reduce

hydrocarbon and carbon monoxide emissions. They were also used on gasoline

engines in American- and Canadian-market automobiles until 1981. Because of their

inability to control oxides of nitrogen, they were superseded by three-way converters.

[edit]Three-way

Since 1981, three-way (oxidation-reduction) catalytic converters have been used in

vehicle emission control systems in the United States and Canada; many other

countries have also adopted stringentvehicle emission regulations that in effect

require three-way converters on gasoline-powered vehicles. A three-way catalytic

converter has three simultaneous tasks:

1. Reduction  of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2

2. Oxidation  of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2

3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxH2x+2 +

[(3x+1)/2]O2 → xCO2 + (x+1)H2O

These three reactions occur most efficiently when the catalytic converter receives

exhaust from an engine running slightly above the stoichiometric point. This point is

between 14.6 and 14.8 parts air to 1 part fuel, by weight, for gasoline. The ratio

for Autogas (or liquefied petroleum gas (LPG)), natural gas and ethanol fuels is each

slightly different, requiring modified fuel system settings when using those fuels. In

general, engines fitted with 3-way catalytic converters are equipped with

a computerized closed-loop feedback fuel injection system using one or more oxygen

sensors, though early in the deployment of three-way

converters, carburetors equipped for feedback mixture control were used.

Three-way catalysts are effective when the engine is operated within a narrow band of

air-fuel ratios near stoichiometry, such that the exhaust gas oscillates between rich

(excess fuel) and lean (excess oxygen) conditions. However, conversion efficiency

falls very rapidly when the engine is operated outside of that band of air-fuel ratios.

Under lean engine operation, there is excess oxygen and the reduction of NOx is not

favored. Under rich conditions, the excess fuel consumes all of the available oxygen

prior to the catalyst, thus only stored oxygen is available for the oxidation function.

Closed-loop control systems are necessary because of the conflicting requirements

for effective NOx reduction and HC oxidation. The control system must prevent the

NOx reduction catalyst from becoming fully oxidized, yet replenish the oxygen storage

material to maintain its function as an oxidation catalyst.

[edit]Oxygen storage

Three-way catalytic converters can store oxygen from the exhaust gas stream, usually

when the air-fuel ratio goes lean.[6] When insufficient oxygen is available from the

exhaust stream, the stored oxygen is released and consumed (see cerium(IV) oxide).

A lack of sufficient oxygen occurs either when oxygen derived from NOx reduction is

unavailable or when certain maneuvers such as hard acceleration enrich the mixture

beyond the ability of the converter to supply oxygen.

[edit]Unwanted reactions

Unwanted reactions can occur in the three-way catalyst, such as the formation of

odoriferous hydrogen sulfide and ammonia. Formation of each can be limited by

modifications to the washcoat and precious metals used. It is difficult to eliminate

these byproducts entirely. Sulfur-free or low-sulfur fuels eliminate or reduce hydrogen

sulfide.

For example, when control of hydrogen-sulfide emissions is

desired, nickel or manganese is added to the washcoat. Both substances act to block

the absorption of sulfur by the washcoat. Hydrogen sulfide is formed when the

washcoat has absorbed sulfur during a low-temperature part of the operating cycle,

which is then released during the high-temperature part of the cycle and the sulfur

combines with HC.

[edit]For diesel engines

For compression-ignition (i.e., diesel engines), the most-commonly-used catalytic

converter is the Diesel Oxidation Catalyst (DOC). This catalyst uses O2 (oxygen) in

the exhaust gas stream to convert CO (carbon monoxide) to CO2 (carbon dioxide) and

HC (hydrocarbons) to H2O (water) and CO2. These converters often operate at 90

percent efficiency, virtually eliminating diesel odor and helping to reduce

visible particulates (soot). These catalyst are not active for NOx reduction because any

reductant present would react first with the high concentration of O2 in diesel exhaust

gas.

Reduction in NOx emissions from compression-ignition engine has previously been

addressed by the addition of exhaust gas to incoming air charge, known as exhaust

gas recirculation (EGR). In 2010, most light-duty diesel manufactures in the U.S.

added catalytic systems to their vehicles to meet new federal emissions requirements.

There are two techniques that have been developed for the catalytic reduction of

NOx emissions under lean exhaust condition - selective catalytic reduction (SCR) and

the lean NOx trap or NOx adsorber. Instead of precious metal-containing NOx

adsorbers, most manufacturers selected base-metal SCR systems that use

a reagent such as ammonia to reduce the NOx into nitrogen. Ammonia is supplied to

the catalyst system by the injection of urea into the exhaust, which then undergoes

thermal decomposition and hydrolysis into ammonia. One trademark product of urea

solution, also referred to as Diesel Emission Fluid (DEF), is AdBlue.

Diesel exhaust contains relatively high levels of particulate matter (soot), consisting in

large part of elemental carbon. Catalytic converters cannot clean up elemental

carbon, though they do remove up to 90 percent of the soluble organic fraction[citation

needed], so particulates are cleaned up by a soot trap or diesel particulate filter (DPF). A

DPF consists of a Cordierite or Silicon Carbide substrate with a geometry that forces

the exhaust flow through the substrate walls, leaving behind trapped soot particles. As

the amount of soot trapped on the DPF increases, so does the back pressure in the

exhaust system. Periodic regenerations (high temperature excursions) are required to

initiate combustion of the trapped soot and thereby reducing the exhaust back

pressure. The amount of soot loaded on the DPF prior to regeneration may also be

limited to prevent extreme exotherms from damaging the trap during regeneration. In

the U.S., all on-road light, medium and heavy-duty vehicles powered by diesel and

built after January 1, 2007, must meet diesel particulate emission limits that means

they effectively have to be equipped with a 2-Way catalytic converter and a diesel

particulate filter. Note that this applies only to the diesel engine used in the vehicle. As

long as the engine was manufactured before January 1, 2007, the vehicle is not

required to have the DPF system. This led to an inventory runup by engine

manufacturers in late 2006 so they could continue selling pre-DPF vehicles well into

2007.[7]

[edit]Lean Burn Spark Ignition Engines

For Lean Burn spark-ignition engines, an oxidation catalyst is used in the same

manner as in a diesel engine. Emissions from Lean Burn Spark Ignition Engines are

very similar to emissions from a Diesel Compression Ignition engine.

[edit]Installation

Many vehicles have a close-coupled catalysts located near the engine's exhaust

manifold. This unit heats up quickly due to its proximity to the engine, and reduces

cold-engine emissions by burning off hydrocarbons from the extra-rich mixture used to

start a cold engine.

In the past, some three-way catalytic converter systems used an air-injection tube

between the first (NOx reduction) and second (HC and CO oxidation) stages of the

converter. This tube was part of asecondary air injection system. The injected air

provided oxygen for the oxidation reactions. An upstream air injection point was also

sometimes present to provide oxygen during engine warmup, which caused unburned

fuel to ignite in the exhaust tract before reaching the catalytic converter. This cleaned

up the exhaust and reduced the engine runtime needed for the catalytic converter to

reach its "light-off" or operating temperature.

Most modern catalytic converter systems do not have air injection systems.[citation

needed] Instead, they provide a constantly varying air-fuel mixture that quickly and

continually cycles between lean and rich exhaust. Oxygen sensors are used to

monitor the exhaust oxygen content before and after the catalytic converter and this

information is used by the Electronic control unit to adjust the fuel injection so as to

prevent the first (NOx reduction) catalyst from becoming oxygen-loaded while ensuring

the second (HC and CO oxidization) catalyst is sufficiently oxygen-saturated. The

reduction and oxidation catalysts are typically contained in a common housing,

however in some instances they may be housed separately.

Damage

Poisoning

Catalyst poisoning occurs when the catalytic converter is exposed to exhaust

containing substances that coat the working surfaces, encapsulating the catalyst so

that it cannot contact and treat the exhaust. The most-notable contaminant is lead, so

vehicles equipped with catalytic converters can be run only on unleaded gasoline.

Other common catalyst poisons include fuel sulfur, manganese(originating primarily

from the gasoline additive MMT), and silicone, which can enter the exhaust stream if

the engine has a leak, allowing coolant into the combustion chamber. Phosphorus is

another catalyst contaminant. Although phosphorus is no longer used in gasoline, it

(and zinc, another low-level catalyst contaminant) was until recently widely used in

engine oil antiwear additives such aszinc dithiophosphate (ZDDP). Beginning in 2006,

a rapid phaseout of ZDDP in engine oils began.[citation needed]

Depending on the contaminant, catalyst poisoning can sometimes be reversed by

running the engine under a very heavy load for an extended period of time. The

increased exhaust temperature can sometimes liquefy or sublime the contaminant,

removing it from the catalytic surface. However, removal of lead deposits in this

manner is usually not possible because of lead's high boiling point.

Meltdown

Any condition that causes abnormally high levels of unburned hydrocarbons — raw or

partially burnt fuel — to reach the converter will tend to significantly elevate its

temperature, bringing the risk of a meltdown of the substrate and resultant catalytic

deactivation and severe exhaust restriction. Vehicles equipped with OBD-II diagnostic

systems are designed to alert the driver to a misfire condition by means of flashing the

"check engine" light on the dashboard.

Emissions regulations vary considerably from jurisdiction to jurisdiction. The earliest

on-road regulations which forced the use of Catalytic converters were the California

For Non-Road regulations California led the way with its 2001 Large Spark Ignition

Engine Regulation. This was followed by the United States Environmental Protection

Agency 50 State Program forNon-Road spark-ignition engines of over 25 brake

horsepower (19 kW) output built after January 1, 2004, are equipped with three-way

catalytic converters. In Japan, a similar set of regulations came into effect January 1,

2007. The European Union has regulations[8] beginning with Euro 1 regulations in

1992 and becoming progressively more stringent in subsequent years.[9]

Most automobile spark-ignition engines in North America have been fitted with

catalytic converters since the mid-1970s, and the technology used in non-automotive

applications is generally based on automotive technology.

Regulations for diesel engines are similarly varied, with some jurisdictions focusing on

NOx (nitric oxide and nitrogen dioxide) emissions and others focusing on particulate

(soot) emissions. This regulatory diversity is challenging for manufacturers of engines,

as it may not be economical to design an engine to meet two sets of regulations.

Regulations of fuel quality vary across jurisdictions. In North America, Europe, Japan

and Hong Kong, gasoline and diesel fuel are highly regulated, and compressed

natural gas and LPG (Autogas) are being reviewed for regulation. In most of Asia and

Africa, the regulations are often lax — in some places sulfur content of the fuel can

reach 20,000 parts per million (2%). Any sulfur in the fuel can be oxidized to

SO2 (sulfur dioxide) or even SO3 (sulfur trioxide) in the combustion chamber. If sulfur

passes over a catalyst, it may be further oxidized in the catalyst, i.e., SO2 may be

further oxidized to SO3. Sulfur oxides are precursors to sulfuric acid, a major

component of acid rain. While it is possible to add substances such as vanadium to

the catalyst washcoat to combat sulfur-oxide formation, such addition will reduce the

effectiveness of the catalyst. The most effective solution is to further refine fuel at the

refinery to produce ultra-low sulfur diesel. Regulations in Japan, Europe and North

America tightly restrict the amount of sulfur permitted in motor fuels. However, the

expense of producing such clean fuel may make it impractical for use in developing

countries. As a result, cities in these countries with high levels of vehicular traffic

suffer from acid rain, which damages stone and woodwork of buildings, poisons

humans and other animals, and damages local ecosystems.

Negative aspects

Some early converter designs greatly restricted the flow of exhaust, which negatively

affected vehicle performance, driveability, and fuel economy.[10] Because they were

used with carburetors incapable of precise fuel-air mixture control, they could

overheat and set fire to flammable materials under the car.[11] Removing a modern

catalytic converter in new condition will not increase vehicle performance without

retuning,[12] but their removal or "gutting" continues.[10][13] The exhaust section where

the converter was may be replaced with a welded-in section of straight pipe, or a

flanged section of "test pipe" legal for off-road use that can then be replaced with a

similarly fitted converter-choked section for legal on-road use, or emissions testing.[12] In the U.S. and many other jurisdictions, it is illegal to remove or disable a catalytic

converter for any reason other than its immediate replacement[citation needed]. It is a

violation of Section 203(a)(3)(A) of the 1990 Clean Air Act for a vehicle owner to

remove a converter from their own vehicle. Section 203(a)(3)(B) makes it illegal for

any person to sell or to install any part where a principle effect would be to bypass,

defeat, or render inoperative any device or element of design of a vehicles emission

control system. Vehicles without functioning catalytic converters generally fail

emission inspections. The automotive aftermarket supplies high-flow converters for

vehicles with upgraded engines, or whose owners prefer an exhaust system with

larger-than-stock capacity.[14]

Warm-up period

Most of the pollution put out by a car occurs during the first five minutes before the

catalytic converter has warmed up sufficiently.[15]

In 1999, BMW introduced the Electric Catalytic Convert, or "E-CAT", in their

flagship E38 750iL sedan. Coils inside the catalytic converter assemblies are heated

electrically just after engine start, bringing the catalyst up to operating temperature

much faster than traditional catalytic converters can, providing cleaner cold starts

and low emission vehicle (LEV) compliance.[citation needed]

Environmental impact

Catalytic converters have proven to be reliable and effective in reducing noxious

tailpipe emissions. However, they may have some adverse environmental impacts in

use:

The requirement for an internal combustion engine equipped with a three-way

catalyst to run at the stoichiometric point means it is less efficient than if it were

operated lean. Thus, there is an increases the amount of fossil fuel consumed and

the carbon-dioxide emissions from the vehicle. However, NOx control on lean-burn

engines is problematic and requires special lean NOx catalysts to meet U.S.

emissions regulations.[citation needed]

Although catalytic converters are effective at removing hydrocarbons and other

harmful emissions, they do not solve the fundamental problem created by burning

a fossil fuel. In addition to water, the main combustion product in exhaust gas

leaving the engine — through a catalytic converter or not — is carbon dioxide

(CO2).[16] Carbon dioxide produced from fossil fuels is one of the greenhouse

gases indicated by the Intergovernmental Panel on Climate Change (IPCC) to be a

"most likely" cause of global warming.[17] Additionally, the U.S. EPA has stated

catalytic converters are a significant and growing cause of global warming,

because of their release of nitrous oxide (N2O), a greenhouse gas over three

hundred times more potent than carbon dioxide.[18]

Catalytic converter production requires palladium or platinum; part of the world

supply of these precious metals is produced near Norilsk, Russia, where the

industry (among others) has caused Norilsk to be added to Time magazine's list of

most-polluted places.[19]

Theft

Because of the external location and the use of valuable precious metals

including platinum, palladium, and rhodium, converters are a target for thieves. The

problem is especially common among late-model Toyota trucks and SUVs, because

of their high ground clearance and easily removed bolt-on catalytic converters.

Welded-in converters are also at risk of theft from SUVs and trucks, as they can be

easily removed.[20][21] Theft removal of the converter can often inadvertently damage

the car's wiring or fuel line resulting in dangerous consequences. Rises in metal costs

in the U.S. during recent years have led to a large increase in theft incidents of the

converter,[22] which can then cost well over $1,000 to replace.[23]

Diagnostics

Various jurisdictions now legislate on-board diagnostics to monitor the function and

condition of the emissions-control system, including the catalytic converter. On-board

diagnostic systems take several forms.

Temperature sensors

Temperature sensors are used for two purposes. The first is as a warning system,

typically on two-way catalytic converters such as are still sometimes used on LPG

forklifts. The function of the sensor is to warn of catalytic converter temperature above

the safe limit of 750 °C (1,380 °F). More-recent catalytic-converter designs are not as

susceptible to temperature damage and can withstand sustained temperatures of 900

°C (1,650 °F).[citation needed] Temperature sensors are also used to monitor catalyst

functioning — usually two sensors will be fitted, with one before the catalyst and one

after to monitor the temperature rise over the catalytic-converter core. For every 1% of

CO in the exhaust gas stream, the exhaust gas temperature will rise by 100 °C.[citation

needed]

Oxygen sensors

The oxygen sensor is the basis of the closed-loop control system on a spark-ignited

rich-burn engine; however, it is also used for diagnostics. In vehicles with OBD II, a

second oxygen sensor is fitted after the catalytic converter to monitor the O2 levels.

The on-board computer makes comparisons between the readings of the two sensors.

If both sensors show the same output, the computer recognizes that the catalytic

converter either is not functioning or has been removed, and will operate a "check

engine" light and retard engine performance. Simple "oxygen sensor simulators" have

been developed to circumvent this problem by simulating the change across the

catalytic converter with plans and pre-assembled devices available on the Internet.

Although these are not legal for on-road use, they have been used with mixed results.[24] Similar devices apply an offset to the sensor signals, allowing the engine to run a

more fuel-economical lean burn that may, however, damage the engine or the

catalytic converter.[25]

NOx sensors

NOx sensors are extremely expensive and are in general used only when a

compression-ignition engine is fitted with a selective catalytic-reduction (SCR)

converter, or a NOx absorber catalyst in a feedback system. When fitted to an SCR

system, there may be one or two sensors. When one sensor is fitted it will be pre-

catalyst; when two are fitted, the second one will be post-catalyst. They are used for

the same reasons and in the same manner as an oxygen sensor — the only

difference is the substance being monitored.

Electronic Engine Management

GM Powertrain has long been a pioneer in offering electronic engine management for

industrial engines,adapting the technology that has transformed the automotive

industry to the specific needs of the industrial environment. The "brain" in every GM

Powertrain engine management system is an Electronic Control Module (ECM) which

was developed specifically for the industrial engine market. The ECM takes input from

various sensors and then uses that data to continually optimize engine operation and

performance. For example, if the engine knock sensor indicates there is premature

detonation, the ECM instantly adjusts spark timing to eliminate the problem. In

industrial applications, this can greatly increase the service life of the engine

For maximum reliability, GM Powertrain's commercial ECMs are manufactured using

thick-film hybrid technology, a technology more advanced than what is used in much

of the automotive industry. The circuits are formed by printing layers of conductive

and nonconductive ink onto a ceramic substrate. The result is an extremely rugged

and durable module that can handle very high temperatures and severe vibrations.

This enables the OEM to mount the ECM directly onto the engine. It is one example

of GM Powertrain's dedication to meeting the specific needs of the industrial engine

market

UNIT 2 ENGINE AUXILIARY SYSTEMS

Carburetor

Principles

The carburetor works on Bernoulli's principle: the faster air moves, the lower its static

pressure, and the higher its dynamic pressure. The throttle (accelerator) linkage does

not directly control the flow of liquid fuel. Instead, it actuates carburetor mechanisms

which meter the flow of air being pulled into the engine. The speed of this flow, and

therefore its pressure, determines the amount of fuel drawn into the airstream.

When carburetors are used in aircraft with piston engines, special designs and

features are needed to prevent fuel starvation during inverted flight. Later engines

used an early form of fuel injection known as a pressure carburetor.

Most production carbureted (as opposed to fuel-injected) engines have a single

carburetor and a matching intake manifold that divides and transports the air fuel

mixture to the intake valves, though some engines (like motorcycle engines) use

multiple carburetors on split heads. Multiple carburetor engines were also common

enhancements for modifying engines in the USA from the 1950s to mid-1960s, as well

as during the following decade of high-performance muscle cars fueling different

chambers of the engine's intake manifold.

Older engines used updraft carburetors, where the air enters from below the

carburetor and exits through the top. This had the advantage of never "flooding" the

engine, as any liquid fuel droplets would fall out of the carburetor instead of into

the intake manifold; it also lent itself to use of an oil bath air cleaner, where a pool of

oil below a mesh element below the carburetor is sucked up into the mesh and the air

is drawn through the oil-covered mesh; this was an effective system in a time when

paper air filters did not exist.

Beginning in the late 1930s, downdraft carburetors were the most popular type for

automotive use in the United States. In Europe, the sidedraft carburetors replaced

downdraft as free space in the engine bay decreased and the use of the SU-type

carburetor (and similar units from other manufacturers) increased. Some small

propeller-driven aircraft engines still use the updraft carburetor design.

Outboard motor carburetors are typically sidedraft, because they must be stacked one

on top of the other in order to feed the cylinders in a vertically oriented cylinder block.

1979 Evinrude Type I marine sidedraft carburetor

The main disadvantage of basing a carburetor's operation on Bernoulli's principle is

that, being a fluid dynamic device, the pressure reduction in a venturi tends to be

proportional to the square of the intake air speed. The fuel jets are much smaller and

limited mainly by viscosity, so that the fuel flow tends to be proportional to the

pressure difference. So jets sized for full power tend to starve the engine at lower

speed and part throttle. Most commonly this has been corrected by using multiple jets.

In SU and other movable jet carburetors, it was corrected by varying the jet size. For

cold starting, a different principle was used, in multi-jet carburetors. A flow resisting

valve called a choke, similar to the throttle valve, was placed upstream of the main jet

to reduce the intake pressure and suck additional fuel out of the jets.

[edit]Operation

Fixed-venturi, in which the varying air velocity in the venturi alters the fuel flow;

this architecture is employed in most carburetors found on cars.

Variable-venturi, in which the fuel jet opening is varied by the slide (which

simultaneously alters air flow). In "constant depression" carburetors, this is done by

a vacuum operated piston connected to a tapered needle which slides inside the

fuel jet. A simpler version exists, most commonly found on small motorcycles and

dirt bikes, where the slide and needle is directly controlled by the throttle position.

The most common variable venturi (constant depression) type carburetor is the

sidedraft SU carburetor and similar models from Hitachi, Zenith-Stromberg and

other makers. The UK location of the SU and Zenith-Stromberg companies helped

these carburetors rise to a position of domination in the UK car market, though

such carburetors were also very widely used on Volvos and other non-UK makes.

Other similar designs have been used on some European and a few Japanese

automobiles. These carburetors are also referred to as "constant velocity" or

"constant vacuum" carburetors. An interesting variation was Ford's VV (Variable

Venturi) carburetor, which was essentially a fixed venturi carburetor with one side

of the venturi hinged and movable to give a narrow throat at low rpm and a wider

throat at high rpm. This was designed to provide good mixing and airflow over a

range of engine speeds, though the VV carburetor proved problematic in service.

A high performance 4-barrel carburetor.

Under all engine operating conditions, the carburetor must:

Measure the airflow of the engine

Deliver the correct amount of fuel to keep the fuel/air mixture in the proper

range (adjusting for factors such as temperature)

Mix the two finely and evenly

This job would be simple if air and gasoline (petrol) were ideal fluids; in practice,

however, their deviations from ideal behavior due to viscosity, fluid drag, inertia, etc.

require a great deal of complexity to compensate for exceptionally high or low engine

speeds. A carburetor must provide the proper fuel/air mixture across a wide range of

ambient temperatures, atmospheric pressures, engine speeds and loads,

and centrifugal forces:

Cold start

Hot start

Idling or slow-running

Acceleration

High speed / high power at full throttle

Cruising at part throttle (light load)

In addition, modern carburetors are required to do this while maintaining low rates

of exhaust emissions.

To function correctly under all these conditions, most carburetors contain a complex

set of mechanisms to support several different operating modes, called circuits.

[edit]Basics

Cross-sectional schematic of a downdraft carburetor

A carburetor basically consists of an open pipe through which the air passes into

the inlet manifold of the engine. The pipe is in the form of a venturi: it narrows in

section and then widens again, causing the airflow to increase in speed in the

narrowest part. Below the venturi is a butterfly valve called the throttle valve — a

rotating disc that can be turned end-on to the airflow, so as to hardly restrict the flow

at all, or can be rotated so that it (almost) completely blocks the flow of air. This valve

controls the flow of air through the carburetor throat and thus the quantity of air/fuel

mixture the system will deliver, thereby regulating engine power and speed. The

throttle is connected, usually through a cable or a mechanical linkage of rods and

joints or rarely by pneumatic link, to the accelerator pedal on a car or the equivalent

control on other vehicles or equipment.

Fuel is introduced into the air stream through small holes at the narrowest part of the

venturi and at other places where pressure will be lowered when not running on full

throttle. Fuel flow is adjusted by means of precisely calibrated orifices, referred to

as jets, in the fuel path.

[edit]Off-idle circuit

As the throttle is opened up slightly from the fully closed position, the throttle plate

uncovers additional fuel delivery holes behind the throttle plate where there is a low

pressure area created by the throttle plate blocking air flow; these allow more fuel to

flow as well as compensating for the reduced vacuum that occurs when the throttle is

opened, thus smoothing the transition to metering fuel flow through the regular open

throttle circuit.

[edit]Main open-throttle circuit

As the throttle is progressively opened, the manifold vacuum is lessened since there

is less restriction on the airflow, reducing the flow through the idle and off-idle circuits.

This is where the venturishape of the carburetor throat comes into play, due

to Bernoulli's principle (i.e., as the velocity increases, pressure falls). The venturi

raises the air velocity, and this high speed and thus low pressure sucks fuel into the

airstream through a nozzle or nozzles located in the center of the venturi. Sometimes

one or more additional booster venturis are placed coaxially within the primary

venturi to increase the effect.

As the throttle is closed, the airflow through the venturi drops until the lowered

pressure is insufficient to maintain this fuel flow, and the idle circuit takes over again,

as described above.

Bernoulli's principle, which is a function of the velocity of the fluid, is a dominant effect

for large openings and large flow rates, but since fluid flow at small scales and low

speeds (low Reynolds number) is dominated by viscosity, Bernoulli's principle is

ineffective at idle or slow running and in the very small carburetors of the smallest

model engines. Small model engines have flow restrictions ahead of the jets to reduce

the pressure enough to suck the fuel into the air flow. Similarly the idle and slow

running jets of large carburetors are placed after the throttle valve where the pressure

is reduced partly by viscous drag, rather than by Bernoulli's principle. The most

common rich mixture device for starting cold engines was the choke, which works on

the same principle.

[edit]Power valve

For open throttle operation a richer mixture will produce more power, prevent pre-

ignition detonation, and keep the engine cooler. This is usually addressed with a

spring-loaded "power valve", which is held shut by engine vacuum. As the throttle

opens up, the vacuum decreases and the spring opens the valve to let more fuel into

the main circuit. On two-stroke engines, the operation of the power valve is the

reverse of normal — it is normally "on" and at a set rpm it is turned "off". It is activated

at high rpm to extend the engine's rev range, capitalizing on a two-stroke's tendency

to rev higher momentarily when the mixture is lean.

Alternative to employing a power valve, the carburetor may utilize a metering

rod or step-up rod system to enrich the fuel mixture under high-demand conditions.

Such systems were originated by Carter Carburetor[citation needed] in the 1950s for the

primary two venturis of their four barrel carburetors, and step-up rods were widely

used on most 1-, 2-, and 4-barrel Carter carburetors through the end of production in

the 1980s. The step-up rods are tapered at the bottom end, which extends into the

main metering jets. The tops of the rods are connected to a vacuum piston and/or a

mechanical linkage which lifts the rods out of the main jets when the throttle is opened

(mechanical linkage) and/or when manifold vacuum drops (vacuum piston). When the

step-up rod is lowered into the main jet, it restricts the fuel flow. When the step-up rod

is raised out of the jet, more fuel can flow through it. In this manner, the amount of fuel

delivered is tailored to the transient demands of the engine. Some 4-barrel

carburetors use metering rods only on the primary two venturis, but some use them

on both primary and secondary circuits, as in the Rochester Quadrajet.

[edit]Accelerator pump

Liquid gasoline, being denser than air, is slower than air to react to a force applied to

it. When the throttle is rapidly opened, airflow through the carburetor increases

immediately, faster than the fuel flow rate can increase. This transient oversupply of

air causes a lean mixture, which makes the engine misfire (or "stumble")—an effect

opposite what was demanded by opening the throttle. This is remedied by the use of a

small piston or diaphragm pump which, when actuated by the throttle linkage, forces a

small amount of gasoline through a jet into the carburetor throat.[4] This extra shot of

fuel counteracts the transient lean condition on throttle tip-in. Most accelerator pumps

are adjustable for volume and/or duration by some means. Eventually the seals

around the moving parts of the pump wear such that pump output is reduced; this

reduction of the accelerator pump shot causes stumbling under acceleration until the

seals on the pump are renewed.

The accelerator pump is also used to prime the engine with fuel prior to a cold start.

Excessive priming, like an improperly adjusted choke, can cause flooding. This is

when too much fuel and not enough air are present to support combustion. For this

reason, most carburetors are equipped with an unloader mechanism: The accelerator

is held at wide open throttle while the engine is cranked, the unloader holds the choke

open and admits extra air, and eventually the excess fuel is cleared out and the

engine starts.

[edit]Choke

When the engine is cold, fuel vaporizes less readily and tends to condense on the

walls of the intake manifold, starving the cylinders of fuel and making the engine

difficult to start; thus, a richer mixture (more fuel to air) is required to start and run

the engine until it warms up. A richer mixture is also easier to ignite.

To provide the extra fuel, a choke is typically used; this is a device that restricts the

flow of air at the entrance to the carburetor, before the venturi. With this restriction in

place, extra vacuum is developed in the carburetor barrel, which pulls extra fuel

through the main metering system to supplement the fuel being pulled from the idle

and off-idle circuits. This provides the rich mixture required to sustain operation at low

engine temperatures.

In addition, the choke can be connected to a cam (the fast idle cam) or other such

device which prevents the throttle plate from closing fully while the choke is in

operation. This causes the engine to idle at a higher speed. Fast idle serves as a way

to help the engine warm up quickly, and give a more stable idle while cold by

increasing airflow throughout the intake system which helps to better atomize the cold

fuel.

In many carbureted cars, the choke is controlled by a cable connected to a pull-knob

on the dashboard operated by the driver. In some carbureted cars it is automatically

controlled by a thermostatemploying a bimetallic spring, which is exposed to engine

heat, or to an electric heating element. This heat may be transferred to the choke

thermostat via simple convection, via engine coolant, or via air heated by the exhaust.

More recent designs use the engine heat only indirectly: A sensor detects engine heat

and varies electrical current to a small heating element, which acts upon the bimetallic

spring to control its tension, thereby controlling the choke. A choke unloader is a

linkage arrangement that forces the choke open against its spring when the vehicle's

accelerator is moved to the end of its travel. This provision allows a "flooded" engine

to be cleared out so that it will start.

Some carburetors do not have a choke but instead use a mixture enrichment circuit,

or enrichener. Typically used on small engines, notably motorcycles, enricheners

work by opening a secondary fuel circuit below the throttle valves. This circuit works

exactly like the idle circuit, and when engaged it simply supplies extra fuel when the

throttle is closed.

Classic British motorcycles, with side-draft slide throttle carburetors, used another

type of "cold start device", called a "tickler". This is simply a spring-loaded rod that,

when depressed, manually pushes the float down and allows excess fuel to fill the

float bowl and flood the intake tract. If the "tickler" is held down too long it also floods

the outside of the carburetor and the crankcase below, and is therefore a fire hazard.

[edit]Other elements

The interactions between each circuit may also be affected by various mechanical or

air pressure connections and also by temperature sensitive and electrical

components. These are introduced for reasons such as response, fuel

efficiency or automobile emissions control. Various air bleeds (often chosen from a

precisely calibrated range, similarly to the jets) allow air into various portions of the

fuel passages to enhance fuel delivery and vaporization. Extra refinements may be

included in the carburetor/manifold combination, such as some form of heating to aid

fuel vaporization such as anearly fuel evaporator.

[edit]Fuel supply

[edit]Float chamber

Holley "Visi-Flo" model #1904 carburetors from the 1950s, factory equipped with transparent glass

bowls.

To ensure a ready mixture, the carburetor has a "float chamber" (or "bowl") that

contains a quantity of fuel at near-atmospheric pressure, ready for use. This reservoir

is constantly replenished with fuel supplied by a fuel pump. The correct fuel level in

the bowl is maintained by means of a float controlling an inletvalve, in a manner very

similar to that employed in a cistern (e.g. a toilet tank). As fuel is used up, the float

drops, opening the inlet valve and admitting fuel. As the fuel level rises, the float rises

and closes the inlet valve. The level of fuel maintained in the float bowl can usually be

adjusted, whether by a setscrew or by something crude such as bending the arm to

which the float is connected. This is usually a critical adjustment, and the proper

adjustment is indicated by lines inscribed into a window on the float bowl, or a

measurement of how far the float hangs below the top of the carburetor when

disassembled, or similar. Floats can be made of different materials, such as

sheet brass soldered into a hollow shape, or of plastic; hollow floats can spring small

leaks and plastic floats can eventually become porous and lose their flotation; in either

case the float will fail to float, fuel level will be too high, and the engine will not run

unless the float is replaced. The valve itself becomes worn on its sides by its motion in

its "seat" and will eventually try to close at an angle, and thus fails to shut off the fuel

completely; again, this will cause excessive fuel flow and poor engine operation.

Conversely, as the fuel evaporates from the float bowl, it leaves sediment, residue,

and varnishes behind, which clog the passages and can interfere with the float

operation. This is particularly a problem in automobiles operated for only part of the

year and left to stand with full float chambers for months at a time; commercial fuel

stabilizer additives are available that reduce this problem.

Usually, special vent tubes allow air to escape from the chamber as it fills or enter as

it empties, maintaining atmospheric pressure within the float chamber; these usually

extend into the carburetor throat. Placement of these vent tubes can be somewhat

critical to prevent fuel from sloshing out of them into the carburetor, and sometimes

they are modified with longer tubing. Note that this leaves the fuel at atmospheric

pressure, and therefore it cannot travel into a throat which has been pressurized by

a supercharger mounted upstream; in such cases, the entire carburetor must be

contained in an airtight pressurized box to operate. This is not necessary in

installations where the carburetor is mounted upstream of the supercharger, which is

for this reason the more frequent system. However, this results in the supercharger

being filled with compressed fuel/air mixture, with a strong tendency to explode should

the engine backfire; this type of explosion is frequently seen in drag races, which for

safety reasons now incorporate pressure releasing blow-off plates on the intake

manifold, breakaway bolts holding the supercharger to the manifold, and shrapnel-

catching ballistic nylon blankets surrounding the superchargers.

If the engine must be operated in any orientation (for example a chain saw), a float

chamber cannot work. Instead, a diaphragm chamber is used. A flexible diaphragm

forms one side of the fuel chamber and is arranged so that as fuel is drawn out into

the engine the diaphragm is forced inward by ambient air pressure. The diaphragm is

connected to the needle valve and as it moves inward it opens the needle valve to

admit more fuel, thus replenishing the fuel as it is consumed. As fuel is replenished

the diaphragm moves out due to fuel pressure and a small spring, closing the needle

valve. A balanced state is reached which creates a steady fuel reservoir level, which

remains constant in any orientation.

[edit]Multiple carburetor barrels

Holley model #2280 2-barrel carburetor

Colombo Type 125 "Testa Rossa" engine in a 1961 Ferrari 250TR Spider with six Weber two-barrel

carburetors inducting air through 12 air horns; one individually adjustable barrel for each cylinder.

While basic carburetors have only one venturi, many carburetors have more than one

venturi, or "barrel". Two barrel and four barrel configurations are commonly used to

accommodate the higher air flow rate with large engine displacement. Multi-barrel

carburetors can have non-identical primary and secondary barrel(s) of different sizes

and calibrated to deliver different air/fuel mixtures; they can be actuated by the linkage

or by engine vacuum in "progressive" fashion, so that the secondary barrels do not

begin to open until the primaries are almost completely open. This is a desirable

characteristic which maximizes airflow through the primary barrel(s) at most engine

speeds, thereby maximizing the pressure "signal" from the venturis, but reduces the

restriction in airflow at high speeds by adding cross-sectional area for greater airflow.

These advantages may not be important in high-performance applications where part

throttle operation is irrelevant, and the primaries and secondaries may all open at

once, for simplicity and reliability; also, V-configuration engines, with two cylinder

banks fed by a single carburetor, may be configured with two identical barrels, each

supplying one cylinder bank. In the widely seen V8 and 4-barrel carburetor

combination, there are often two primary and two secondary barrels.

The spread-bore 4-barrel carburetor, first released by Rochester in the 1965 model

year as the "Quadrajet"[citation needed] has a much greater spreadbetween the sizes of the

primary and secondary throttle bores. The primaries in such a carburetor are quite

small relative to conventional 4-barrel practice, while the secondaries are quite large.

The small primaries aid low-speed fuel economy and drivability, while the large

secondaries permit maximum performance when it is called for. To tailor airflow

through the secondary venturis, each of the secondary throats has an air valve at the

top. This is configured much like a choke plate, and is lightly spring-loaded into the

closed position. The air valve opens progressively in response to engine speed and

throttle opening, gradually allowing more air to flow through the secondary side of the

carburetor. Typically, the air valve is linked to metering rods which are raised as the

air valve opens, thereby adjusting secondary fuel flow.

Multiple carburetors can be mounted on a single engine, often with progressive

linkages; two four-barrel carburetors (often referred to as "dual-quads") were

frequently seen on high performance American V8s, and multiple two barrel

carburetors are often now seen on very high performance engines. Large numbers of

small carburetors have also been used (see photo), though this configuration can limit

the maximum air flow through the engine due to the lack of a common plenum; with

individual intake tracts, not all cylinders are drawing air at once as the engine's

crankshaft rotates.[5]

[edit]Carburetor adjustment

Too much fuel in the fuel-air mixture is referred to as too rich, and not enough fuel is

too lean. The mixture is normally adjusted by one or more needle valveson an

automotive carburetor, or a pilot-operated lever on piston-engined aircraft (since

mixture is air density (altitude) dependent). The (stoichiometric) air togasoline ratio is

14.7:1, meaning that for each weight unit of gasoline, 14.7 units of air will be

consumed. Stoichiometric mixture are different for various fuels other than gasoline.

Ways to check carburetor mixture adjustment include: measuring the carbon

monoxide, hydrocarbon, and oxygen content of the exhaust using a gas analyzer, or

directly viewing the colour of the flame in the combustion chamber through a special

glass-bodied spark plug sold under the name "Colortune"; the flame colour of

stoichiometric burning is described as a "bunsen blue", turning to yellow if the mixture

is rich and whitish-blue if too lean.

The mixture can also be judged by removing and scrutinizing the spark plugs. black,

dry, sooty plugs indicate a mixture too rich; white to light gray plugs indicate a lean

mixture. A proper mixture is indicated by brownish-gray plugs.

In the 1980s, many American-market vehicles used special "feedback" carburetors

that could change the base mixture in response to signals from an exhaust

gas oxygen sensor. These were mainly used because they were less expensive than

fuel injection systems; they worked well enough to meet 1980s emissions

requirements and were based on existing carburetor designs. Eventually, however,

falling hardware prices and tighter emissions standards caused fuel injection to

supplant carburetors in new-vehicle production.

Where multiple carburetors are used the mechanical linkage of their throttles must be

synchronized for smooth engine running.

In this tutorial we will be looking at the Electronic Fuel Injection system, with particular focus upon the sensors and actuators, and their inputs and outputs to and from the vehicle's ECM. The tutorial looks at the multi-point injection system, with single-point being covered in a later tutorial.

Overview

Both the multi-point and the single-point systems operate in a very similar fashion, having an electromechanically operated injector or injectors opening for a predetermined length of time called the injector pulse width. The pulse width is determined by the engine’s Electronic Control Module (ECM and depends on the engine temperature, the engine load and the information from the oxygen (lambda) sensor. The fuel is delivered from the tank through a filter, and a regulator determines its operating pressure. The fuel is delivered to the engine in precise quantities and in most cases is injected into the inlet manifold to await the valve’s opening, then drawn into the combustion chamber by the incoming air.

The Fuel Tank

This is the obvious place to start in any full system explanation. Unlike the tanks on early carburettor-equipped vehicles, it is a sealed unit that allows the natural gassing of the fuel to aid delivery to the pump by slightly pressurising the system. When the filler cap is removed, pressure is heard to escape because the fuel filler caps are no longer vented.

The Fuel Pump

This type of high-pressure fuel pump (Fig 1.0) is called a roller cell pump, with the fuel entering the pump and being compressed by rotating cells which force it through the pump at a high pressure. The pump can produce a pressure of 8 bar (120 psi) with a delivery rate of approximately 4 to 5 litres per minute. Within the pump is a pressure relief valve that lifts off its seat at 8 bar to arrest the pressure if a blockage in the filter or fuel lines or elsewhere causes it to become obstructed. The other end of the pump (output) is home to a non-return valve which, when the voltage to the pump is removed, closes the return to the tank and maintains pressure within the system. The normal operating pressure within this system is approximately 2 bar (30 psi), at which the current draw on the pump is 3 to 5 amps. Fuel passing across the fuel pump's armature is subjected to sparks and arcing; this sounds quite dangerous, but the absence of oxygen means that there will not be an explosion!

Figure 1.0

The majority of fuel pumps fitted to today’s motor vehicles are fitted within the vehicle’s petrol tank and are referred to as ‘submerged’ fuel pumps. The pump is invariably be located with the fuel sender unit and both units can sometimes be accessed through an inspection hole either in the boot floor or under the rear seat. Mounted vertically, the pump comprises an inner and outer gear assembly that is called the ‘gerotor’. The combined assembly is secured in the tank using screws and sealed with a rubber gasket, or a bayonet-type locking ring. On some models, there are two fuel pumps, the submerged pump acting as a ‘lift’ pump to the external roller cell pump.

Figure 1.1

Figure 1.2

The waveform illustrated in Fig 1.1 shows the current for each sector of the commutator. The majority of fuel pumps have 6 to 8 sectors, and a repetitive point on the waveform can indicate wear and an impending failure. In the illustration waveform it can be seen that there is a lower current draw on one sector and this is repeated when the pump has rotated through 720°. This example has 8 sectors per rotation.

Fig 1.2 shows typical access to the fuel-submerged pump to measure current draw.

The current drawn by the fuel pump depends upon the fuel pressure but should be no more than 8 amps, as found on the Bosch K-Jetronic mechanical fuel injection which has a system pressure of 75 psi.

Fuel Supply

A conventional ‘flow and return’ system has a supply of fuel delivered to the fuel rail, and the unwanted fuel is passed through the pressure regulator back to the tank. It is the restriction in the fuel line created by the pressure regulator that provides the system operational pressure.

Returnless Fuel Systems

Have been adopted by several motor manufacturers and differ from the conventional by having a delivery pipe only to the fuel rail with no return flow back to the tank.

The returnless systems, both the mechanical and the electronic versions, were necessitated by emissions laws. The absence of heated petrol returning to the fuel tank reduces the amount of evaporative emissions, while the fuel lines are kept short, thus reducing build costs.

Mechanical Returnless Fuel Systems

The ‘returnless’ system differs from the norm by having the pressure regulator inside the fuel tank. When the fuel pump is activated, fuel flows into the system until the required pressure is obtained; at this point ‘excess’ fuel is bled past the pressure regulator and back into the tank.

The ‘flow and return’ system has a vacuum supply to the pressure regulator: this enables the fuel pressure to be increased whenever the manifold vacuum drops, providing fuel enrichment under acceleration.

The ‘returnless’ system has no mechanical compensation affecting the fuel pressure, which remains at a higher than usual 44 to 50 psi. By increasing the delivery pressure, the ECM (Electronic Control Module) can alter the injection pulse width to give the precise delivery, regardless of the engine load and without fuel pressure compensation.

Electronic Returnless Fuel Systems

This version has all the required components fitted within the one unit of the submersible fuel pump. It contains a small particle filter (in addition to the strainer), pump, electronic pressure regulator, fuel level sensor and a sound isolation system. The electronic pressure regulator allows the pressure to be increased under acceleration conditions, and the pump’s output can be adjusted to suit the engine's fuel demand. This prolongs the pump’s life as it is no longer providing a larger than required output delivery.

The Electronic Control Module (ECM) supplies the required pressure information, while the fuel pump’s output signal is supplied in the form of a digital squarewave. Altering the squarewave’s duty cycle affects the pump’s delivery output.

To compensate for the changing viscosity of the fuel with changing fuel temperature, a fuel rail temperature sensor is installed. A pulsation damper may also be fitted ahead of or inside the fuel rail.

Injectors

The injector is an electromechanical device, which is fed by a 12 volt supply from either the fuel injection relay or the ECM. The voltage is present only when the engine is cranking or running, because it is controlled by a tachometric relay. The injector is supplied with fuel from a common fuel rail. The injector pulse width depends on the input signals seen by the ECM from its various engine sensors, and varies to compensate for cold engine starting and warm-up periods, the initial wide pulse getting narrower as the engine warms to operating temperature. The pulse width also expands under acceleration and contracts under light load conditions.

The injector has constant voltage supply while the engine is running and the earth path is switched via the ECM. An example of a typical waveform is shown below in Fig 1.3.

Figure 1.3

Multi-point injection may be either sequential or simultaneous. A simultaneous system fires all 4 injectors at the same time with each cylinder receiving 2 injection pulses per cycle (720° crankshaft rotation). A sequential system receives just 1 injection pulse per cycle, timed to coincide with the opening of the inlet valve. As a very rough guide the injector pulse widths for an engine at normal operating temperature at idle speed are around 2.5 ms for simultaneous and 3.5 ms for sequential.

An electromechanical injector of course takes a short time to react, as it requires a level of magnetism to build before the pintle is lifted off its seat. This time is called the ‘solenoid reaction time’. This delay is important to monitor and can sometimes occupy a third of the total pulse width. A good example of the delay in opening can be seen in the example waveform shown below in Fig 1.4.

The waveform is ‘split’ into two clearly defined areas. The first part of the waveform is responsible for the electromagnetic force lifting the pintle, in this example taking approximately 0.6 ms. At this point the current can be seen to level off before rising again as the pintle is held open. With this level off ind it can be seen that the amount of time that the injector is held open is not necessarily the same as the time measured. It is not however possible to calculate the time taken for the injector’s spring to fully close the injector and cut off the fuel flow.

This test is ideal for identifying an injector with an unacceptably slow solenoid reaction time. Such an injector would not deliver the required amount of fuel and the cylinder in question would run lean.

Figure 1.4

Fig 1.5 shows both the injector voltage and current displayed simultaneously.

Figure 1.5

Fuel injection

Fuel rail connected to the injectors that are mounted just above the intake manifold on a four cylinder

engine.

Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel

delivery system used inautomotive petrol engines, having almost completely replaced carburetors in the late 1980s.

A fuel injection system is designed and calibrated specifically for the type(s) of fuel it will handle. Most fuel injection

systems are for gasoline ordiesel applications. With the advent of electronic fuel injection (EFI), the diesel and

gasoline hardware has become similar. EFI's programmablefirmware has permitted common hardware to be used

with different fuels.

Carburetors were the predominant method used to meter fuel on gasoline engines before the widespread use of fuel

injection. A variety of injection systems have existed since the earliest usage of the internal combustion engine.

The primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel by forcibly

pumping it through a small nozzle under high pressure, while a carburetor relies on suction created by intake air

rushing through a venturi to draw the fuel into the airstream.

Objectives

The functional objectives for fuel injection systems can vary. All share the central task

of supplying fuel to the combustion process, but it is a design decision how a

particular system will be optimized. There are several competing objectives such as:

power output

fuel efficiency

emissions performance

ability to accommodate alternative fuels

reliability

driveability and smooth operation

initial cost

maintenance cost

diagnostic capability

range of environmental operation

Engine tuning

Certain combinations of these goals are conflicting, and it is impractical for a single

engine control system to fully optimize all criteria simultaneously. In practice,

automotive engineers strive to best satisfy a customer's needs competitively. The

modern digital electronic fuel injection system is far more capable at optimizing these

competing objectives consistently than a carburetor. Carburetors have the potential to

atomize fuel better (see Pogue and Allen Caggiano patents).

Benefits

Engine operation

Operational benefits to the driver of a fuel-injected car include smoother and more

dependable engine response during quick throttle transitions, easier and more

dependable engine starting, better operation at extremely high or low ambient

temperatures, increased maintenance intervals, and increased fuel efficiency. On a

more basic level, fuel injection does away with the choke which on carburetor-

equipped vehicles must be operated when starting the engine from cold and then

adjusted as the engine warms up.

An engine's air/fuel ratio must be precisely controlled under all operating conditions to

achieve the desired engine performance, emissions, driveability, and fuel economy.

Modern electronic fuel-injection systems meter fuel very accurately, and use closed

loop fuel-injection quantity-control based on a variety of feedback signals from

an oxygen sensor, a mass airflow (MAF) or manifold absolute pressure (MAP) sensor,

a throttle position (TPS), and at least one sensor on the crankshaft and/or camshaft(s)

to monitor the engine's rotational position. Fuel injection systems can react rapidly to

changing inputs such as sudden throttle movements, and control the amount of fuel

injected to match the engine's dynamic needs across a wide range of operating

conditions such as engine load, ambient air temperature, engine temperature, fuel

octane level, and atmospheric pressure.

A multipoint fuel injection system generally delivers a more accurate and equal mass

of fuel to each cylinder than can a carburetor, thus improving the cylinder-to-cylinder

distribution. Exhaustemissions are cleaner because the more precise and accurate

fuel metering reduces the concentration of toxic combustion byproducts leaving the

engine, and because exhaust cleanup devices such as the catalytic converter can be

optimized to operate more efficiently since the exhaust is of consistent and predictable

composition.

Fuel injection generally increases engine fuel efficiency. With the improved cylinder-

to-cylinder fuel distribution, less fuel is needed for the same power output. When

cylinder-to-cylinder distribution is less than ideal, as is always the case to some

degree with a carburetor or throttle body fuel injection, some cylinders receive excess

fuel as a side effect of ensuring that all cylinders receive sufficientfuel. Power output is

asymmetrical with respect to air/fuel ratio; burning extra fuel in the rich cylinders does

not reduce power nearly as quickly as burning too little fuel in the lean cylinders.

However, rich-running cylinders are undesirable from the standpoint of exhaust

emissions, fuel efficiency, engine wear, and engine oil contamination. Deviations from

perfect air/fuel distribution, however subtle, affect the emissions, by not letting the

combustion events be at the chemically ideal (stoichiometric) air/fuel ratio. Grosser

distribution problems eventually begin to reduce efficiency, and the grossest

distribution issues finally affect power. Increasingly poorer air/fuel distribution affects

emissions, efficiency, and power, in that order. By optimizing the homogeneity of

cylinder-to-cylinder mixture distribution, all the cylinders approach their maximum

power potential and the engine's overall power output improves.

A fuel-injected engine often produces more power than an equivalent carbureted

engine. Fuel injection alone does not necessarily increase an engine's maximum

potential output. Increased airflow is needed to burn more fuel, which in turn releases

more energy and produces more power. The combustion process converts the fuel's

chemical energy into heat energy, whether the fuel is supplied by fuel injectors or a

carburetor. However, airflow is often improved with fuel injection, the components of

which allow more design freedom to improve the air's path into the engine. In contrast,

a carburetor's mounting options are limited because it is larger, it must be carefully

oriented with respect to gravity, and it must be equidistant from each of the engine's

cylinders to the maximum practicable degree. These design constraints generally

compromise airflow into the engine. Furthermore, a carburetor relies on a

restrictive venturi to create a local air pressure difference, which forces the fuel into

the air stream. The flow loss caused by the venturi, however, is small compared to

other flow losses in the induction system. In a well-designed carburetor induction

system, the venturi is not a significant airflow restriction.

Fuel is saved while the car is coasting because the car's movement is helping to keep

the engine rotating, so less fuel is used for this purpose. Control units on modern cars

react to this and reduce or stop fuel flow to the engine reducing wear on the

brakes[citation needed].

History and development

Herbert Akroyd Stuart developed the first system laid out on modern lines (with a

highly accurate 'jerk pump' to meter out fuel oil at high pressure to an injector. This

system was used on the hot bulb engine and was adapted and improved by Robert

Bosch and Clessie Cummins for use on diesel engines — Rudolf Diesel's original

system employed a cumbersome[citation needed] 'air-blast' system using highly compressed

air[clarification needed].

The first use of direct gasoline injection was on the Hesselman engine invented by

Swedish engineer Jonas Hesselman in 1925.[1][2] Hesselman engines use the

ultra lean burn principle; fuel is injected toward the end of the compression stroke,

then ignited with a spark plug. They are often started on gasoline and then switched to

diesel or kerosene.[3] Fuel injection was in widespread commercial use in diesel

engines by the mid-1920s. Because of its greater immunity to wildly changing g-

forces on the engine, the concept was adapted for use in gasoline-powered aircraft

during World War II, and direct injection was employed in some notable designs like

the Junkers Jumo 210, the Daimler-Benz DB 601, the BMW 801, the Shvetsov ASh-

82FN (M-82FN) and later versions of the Wright R-3350used in the B-29

Superfortress.

Alfa Romeo tested one of the very first electric injection systems (Caproni-Fuscaldo)

in Alfa Romeo 6C2500 with "Ala spessa" body in 1940 Mille Miglia. The engine had

six electrically operated injectors and were fed by a semi-high pressure circulating fuel

pump system.[4]

Mechanical

The term Mechanical when applied to fuel injection is used to indicate that metering

functions of the fuel injection (how the correct amount of fuel for any given situation is

determined and delivered) is not achieved electronically but rather through

mechanical means alone.

In the 1940s, hot rodder Stuart Hilborn offered mechanical injection for

racers, salt cars, and midgets.[5]

One of the first commercial gasoline injection systems was a mechanical system

developed by Bosch and introduced in 1952 on the Goliath GP700 and Gutbrod

Superior 600. This was basically a high pressure diesel direct-injection pump with an

intake throttle valve set up. (Diesels only change amount of fuel injected to vary

output; there is no throttle.) This system used a normal gasoline fuel pump, to provide

fuel to a mechanically driven injection pump, which had separate plungers per injector

to deliver a very high injection pressure directly into the combustion chamber.

Another mechanical system, also by Bosch, but injecting the fuel into the port above

the intake valve was later used by Porsche from 1969 until 1973 for the 911

production range and until 1975 on the Carrera 3.0 in Europe. Porsche continued

using it on its racing cars into the late seventies and early eighties. Porsche racing

variants such as the 911 RSR 2.7 & 3.0, 904/6, 906, 907, 908, 910, 917 (in its regular

normally aspirated or 5.5 Liter/1500 HP Turbocharged form), and 935 all

used Bosch or Kugelfischer built variants of injection. The Kugelfischer system was

also used by the BMW 2000/2002 Tii and some versions of the Peugeot 404/504 and

Lancia Flavia. Lucas also offered a mechanical system which was used by some

Maserati, Aston Martin and Triumph models between ca. 1963 and 1973.

A system similar to the Bosch inline mechanical pump was built by SPICA for Alfa

Romeo, used on the Alfa Romeo Montreal and on US market 1750 and 2000 models

from 1969 to 1981. This was specifically designed to meet the US emission

requirements, and allowed Alfa to meet these requirements with no loss in

performance and a reduction in fuel consumption.

Chevrolet introduced a mechanical fuel injection option, made by General

Motors' Rochester Products division, for its 283 V8 engine in 1956 (1957 US model

year). This system directed the inducted engine air across a "spoon shaped" plunger

that moved in proportion to the air volume. The plunger connected to the fuel metering

system which mechanically dispensed fuel to the cylinders via distribution tubes. This

system was not a "pulse" or intermittent injection, but rather a constant flow system,

metering fuel to all cylinders simultaneously from a central "spider" of injection lines.

The fuel meter adjusted the amount of flow according to engine speed and load, and

included a fuel reservoir, which was similar to a carburetor's float chamber. With its

own high-pressure fuel pump driven by a cable from the distributor to the fuel meter,

the system supplied the necessary pressure for injection. This was "port" injection,

however, in which the injectors are located in the intake manifold, very near the intake

valve. (Direct fuel injection is a fairly recent innovation for automobile engines. As

recent as 1954 in the aforementioned Mercedes-Benz 300SL or the Gutbrod in 1953.)

The highest performance version of the fuel injected engine was rated at 283 bhp

(211.0 kW) from 283 cubic inches (4.6 L). This made it among the early production

engines in history to exceed 1 hp/in³ (45.5 kW/L), after Chrysler's Hemi engine and a

number of others. General Motors' fuel injected engine — usually referred to as the

"fuelie" — was optional on the Corvette for the 1957 model year.

During the 1960s, other mechanical injection systems such as Hilborn were

occasionally used on modified American V8 engines in various racing applications

such as drag racing, oval racing, and road racing.[6] These racing-derived systems

were not suitable for everyday street use, having no provisions for low speed metering

or often none even for starting (fuel had to be squirted into the injector tubes while

cranking the engine in order to start it). However they were a favorite in the

aforementioned competition trials in which essentially wide-open throttle operation

was prevalent. Constant-flow injection systems continue to be used at the highest

levels of drag racing, where full-throttle, high-RPM performance is key.[7]

Electronic

The first commercial electronic fuel injection (EFI) system was Electrojector,

developed by the Bendix Corporation and was to be offered by American

Motors (AMC) in 1957.[8][9] A special muscle carmodel, the Rambler Rebel, showcased

AMC's new 327   cu   in (5.4   L) engine . The Electrojector was an option and rated at

288 bhp (214.8 kW).[10] With no Venturi effect or heated carburetor (to help vaporize

the gasoline) AMC's EFI equipped engine breathed easier with denser cold air to pack

more power sooner, reaching peak torque at 500 rpm lower than the equivalent no-

fuel injection engine.[6]The Rebel Owners Manual described the design and operation

of the new system.[11] Initial press information about the Bendix system in December

1956 was followed in March 1957 by a price bulletin that pegged the option

at US$395, but due to supplier difficulties, fuel-injected Rebels would only be available

after June 15.[12] This was to have been the first production EFI engine, but

Electrojector's teething problems meant only pre-production cars were so equipped:

thus, very few cars so equipped were ever sold[13] and none were made available to

the public.[14] The EFI system in the Rambler was a far more-advanced setup than the

mechanical types then appearing on the market and the engines ran fine in warm

weather, but suffered hard starting in cooler temperatures.[12]

Chrysler offered Electrojector on the 1958 Chrysler 300D, Dodge D500, Plymouth

Fury, and DeSoto Adventurer, arguably the first series-production cars equipped with

an EFI system. It was jointly engineered by Chrysler and Bendix. The early electronic

components were not equal to the rigors of underhood service, however, and were too

slow to keep up with the demands of "on the fly" engine control. Most of the 35

vehicles originally so equipped were field-retrofitted with 4-barrel carburetors. The

Electrojector patents were subsequently sold to Bosch.

Bosch developed an electronic fuel injection system, called D-Jetronic (D for Druck,

German for "pressure"), which was first used on the VW 1600TL/E in 1967. This was

a speed/density system, using engine speed and intake manifold air density to

calculate "air mass" flow rate and thus fuel requirements. This system was adopted

by VW, Mercedes-Benz, Porsche, Citroën, Saab, and Volvo. Lucas licensed the

system for production with Jaguar. Bosch superseded the D-Jetronic system with

the K-Jetronic and L-Jetronic systems for 1974, though some cars (such as the Volvo

164) continued using D-Jetronic for the following several years.

Chevrolet Cosworth Vega engine showing Bendix electronic fuel injection

The Cadillac Seville was introduced in 1975 with an EFI system made by Bendix and

modelled very closely on Bosch's D-Jetronic. L-Jetronic first appeared on the 1974

Porsche 914, and uses a mechanical airflow meter (L for Luft, German for "air") that

produces a signal that is proportional to "air volume". This approach required

additional sensors to measure the atmospheric pressure and temperature, to

ultimately calculate "air mass". L-Jetronic was widely adopted on European cars of

that period, and a few Japanese models a short time later.

The limited production Chevrolet Cosworth Vega was introduced in March 1975 using

a Bendix EFI system with pulse-time manifold injection, four injector valves, an

electronic control unit (ECU), five independent sensors and two fuel pumps. The EFI

system was developed to satisfy stringent emission control requirements and market

demands for a technologically advanced responsive vehicle. 5000 hand-built

Cosworth Vega engines were produced but only 3508 cars were sold through 1976.[15]

A major milestone was reached in 1980 when Motorola Corporation introduced the

first engine computer with microprocessor (digital) control, the EEC III module, which

is now the standard approach. The advent of the digital microprocessor permitted the

integration of all powertrain sub-systems into a single control module. [16]

In 1981 Chrysler Corporation introduced an EFI system featuring a sensor that directly

measures the air mass flow into the engine, on the Imperial automobile (5.2L V8) as

standard equipment. The mass air sensor utilizes a heated platinum wire placed in the

incoming air flow. The rate of the wire's cooling is proportional to the air mass flowing

across the wire. Since the hot wire sensor directly measures air mass, the need for

additional temperature and pressure sensors was eliminated. This system was

independently developed and engineered in Highland Park, Michigan and

manufactured at Chrysler's Electronics division in Huntsville, Alabama, USA.[17][18]

Supersession of carburetors

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When efficient combustion takes place in an internal combustion engine, the proper

number of fuel molecules and oxygen molecules are sent to the engine's combustion

chamber(s), where fuel combustion (i.e., fuel oxidation) takes place. When efficient

combustion takes place, neither extra fuel or extra oxygen molecules remain: each

fuel molecule is matched with the appropriate number of oxygen molecules. This

balanced condition is called stoichiometry.

In the 1970s and 1980s in the US, the federal government imposed increasingly

strict exhaust emission regulations. During that time period, the vast majority of

gasoline-fueled automobile and light truck engines did not use fuel injection. To

comply with the new regulations, automobile manufacturers often made extensive and

complex modifications to the engine carburetor(s). While a simple carburetor system

has certain advantages compared to the fuel injection systems that were available

during the 1970s and 1980s (including lower manufacturing cost), the more complex

carburetor systems installed on many engines beginning in the early 1970s did not

usually have these advantages. So in order to more easily comply with government

emissions control regulations, automobile manufacturers, beginning in the late 1970s,

furnished more of their gasoline-fueled engines with fuel injection systems, and fewer

with complex carburetor systems.

There are three primary types of toxic emissions from an internal combustion

engine: Carbon Monoxide (CO), unburnt hydrocarbons (HC), and oxides of

nitrogen (NOx). CO and HC result from incomplete combustion of fuel due to

insufficient oxygen in the combustion chamber. NOx, in contrast, results from

excessive oxygen in the combustion chamber. The opposite causes of these

pollutants makes it difficult to control all three simultaneously. Once the permissible

emission levels dropped below a certain point, catalytic treatment of these three main

pollutants became necessary. This required a particularly large increase in fuel

metering accuracy and precision, for simultaneous catalysis of all three pollutants

requires that the fuel/air mixture be held within a very narrow range of stoichiometry.

The open loop fuel injection systems had already improved cylinder-to-cylinder fuel

distribution and engine operation over a wide temperature range, but did not offer

sufficient fuel/air mixture control to enable effective exhaust catalysis. Closed

loop fuel injection systems improved the air/fuel mixture control with an exhaust

gas oxygen sensor. The O2 sensor is mounted in the exhaust system upstream of the

catalytic converter, and enables the engine management computer to determine and

adjust the air/fuel ratio precisely and quickly.

Fuel injection was phased in through the latter '70s and '80s at an accelerating rate,

with the US, French and German markets leading and the UK and Commonwealth

markets lagging somewhat, and since the early 1990s, almost all gasoline passenger

cars sold in first world markets like the United States, Canada, Europe, Japan, and

Australia have come equipped with electronic fuel injection (EFI). Many motorcycles

still utilize carbureted engines, though all current high-performance designs have

switched to EFI.

Fuel injection systems have evolved significantly since the mid-1980s. Current

systems provide an accurate, reliable and cost-effective method of metering fuel and

providing maximum engine efficiency with clean exhaust emissions, which is why EFI

systems have replaced carburetors in the marketplace. EFI is becoming more reliable

and less expensive through widespread usage. At the same time, carburetors are

becoming less available, and more expensive. Even marine applications are adopting

EFI as reliability improves. Virtually all internal combustion engines, including

motorcycles, off-road vehicles, and outdoor power equipment, may eventually use

some form of fuel injection.

The carburetor remains in use in developing countries where vehicle emissions are

unregulated and diagnostic and repair infrastructure is sparse. Fuel injection is

gradually replacing carburetors in these nations too as they adopt emission

regulations conceptually similar to those in force in Europe, Japan, Australia and

North America. NASCAR will legalize and adopt fuel injectors to take the place of

carburetors starting at the 2012 NASCAR Sprint Cup Series season.[19][20][21]

Basic function

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The process of determining the necessary amount of fuel, and its delivery into the

engine, are known as fuel metering. Early injection systems used mechanical

methods to meter fuel (non electronic, or mechanical fuel injection). Modern systems

are nearly all electronic, and use an electronic solenoid (the injector) to inject the fuel.

An electronic engine control unit calculates the mass of fuel to inject.

Modern fuel injection schemes follow much the same setup. There is a mass airflow

sensor or manifold absolute pressure sensor at the intake, typically mounted either in

the air tube feeding from the air filter box to the throttle body, or mounted directly to

the throttle body itself. The mass airflow sensor does exactly what its name implies; it

senses the mass of the air that flows past it, giving the computer an accurate idea of

how much air is entering the engine. The next component in line is the Throttle Body.

The throttle body has a throttle position sensor mounted onto it, typically on the

butterfly valve of the throttle body. The throttle position sensor (TPS) reports to the

computer the position of the throttle butterfly valve, which the ECM uses to calculate

the load upon the engine. The fuel system consists of a fuel pump (typically mounted

in-tank), a fuel pressure regulator, fuel lines (composed of either high strength plastic,

metal, or reinforced rubber), a fuel rail that the injectors connect to, and the fuel

injector(s). There is a coolant temperature sensor that reports the engine temperature

to the ECM, which the engine uses to calculate the proper fuel ratio required. In

sequential fuel injection systems there is a camshaft position sensor, which the ECM

uses to determine which fuel injector to fire. The last component is the oxygen sensor.

After the vehicle has warmed up, it uses the signal from the oxygen sensor to perform

fine tuning of the fuel trim.

The fuel injector acts as the fuel-dispensing nozzle. It injects liquid fuel directly into the

engine's air stream. In almost all cases this requires an external pump. The pump and

injector are only two of several components in a complete fuel injection system.

In contrast to an EFI system, a carburetor directs the induction air through a venturi,

which generates a minute difference in air pressure. The minute air pressure

differences both emulsify (premix fuel with air) the fuel, and then acts as the force to

push the mixture from the carburetor nozzle into the induction air stream. As more air

enters the engine, a greater pressure difference is generated, and more fuel is

metered into the engine. A carburetor is a self-contained fuel metering system, and is

cost competitive when compared to a complete EFI system.

An EFI system requires several peripheral components in addition to the injector(s), in

order to duplicate all the functions of a carburetor. A point worth noting during times of

fuel metering repair is that early EFI systems are prone to diagnostic ambiguity. A

single carburetor replacement can accomplish what might require numerous repair

attempts to identify which one of the several EFI system components is

malfunctioning. Newer EFI systems since the advent of OBD II diagnostic systems,

can be very easy to diagnose due to the increased ability to monitor the realtime data

streams from the individual sensors. This gives the diagnosing technician realtime

feedback as to the cause of the drivability concern, and can dramatically shorten the

number of diagnostic steps required to ascertain the cause of failure, something which

isn't as simple to do with a carburetor. On the other hand, EFI systems require little

regular maintenance; a carburetor typically requires seasonal and/or altitude

adjustments.

Detailed function

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Note: These examples specifically apply to a modern EFI gasoline engine. Parallels to fuels other than gasoline can be made, but only conceptually.

Typical EFI components

Animated cut through diagram of a typical fuel injector.

Injectors

Fuel Pump

Fuel Pressure Regulator

ECM - Engine Control Module; includes a digital computer and circuitry to

communicate with sensors and control outputs.

Wiring Harness

Various Sensors (Some of the sensors required are listed here.)

Crank/Cam Position: Hall effect sensor Airflow: MAF sensor, sometimes this is inferred with a MAP sensor Exhaust Gas Oxygen: Oxygen sensor, EGO sensor, UEGO sensor

Functional description

Central to an EFI system is a computer called the Engine Control Unit (ECU),

which monitors engine operating parameters via varioussensors. The ECU

interprets these parameters in order to calculate the appropriate amount of fuel to

be injected, among other tasks, and controls engine operation by manipulating fuel

and/or air flow as well as other variables. The optimum amount of injected fuel

depends on conditions such as engine and ambient temperatures, engine speed

and workload, and exhaust gas composition.

The electronic fuel injector is normally closed, and opens to inject pressurized fuel

as long as electricity is applied to the injector's solenoid coil. The duration of this

operation, called the pulse width, is proportional to the amount of fuel desired. The

electric pulse may be applied in closely controlled sequence with the valve events

on each individual cylinder (in a sequential fuel injection system), or in groups of

less than the total number of injectors (in a batch fire system).

Since the nature of fuel injection dispenses fuel in discrete amounts, and since the

nature of the 4-stroke engine has discrete induction (air-intake) events, the ECU

calculates fuel in discrete amounts. In a sequential system, the injected fuel mass

is tailored for each individual induction event. Every induction event, of every

cylinder, of the entire engine, is a separate fuel mass calculation, and each injector

receives a unique pulse width based on that cylinder's fuel requirements.

It is necessary to know the mass of air the engine "breathes" during each induction

event. This is proportional to the intake manifold's air pressure/temperature, which

is proportional to throttle position. The amount of air inducted in each intake event

is known as "air-charge", and this can be determined using several methods.

(See MAF sensor, and MAP sensor.)

The three elemental ingredients for combustion are fuel, air and ignition. However,

complete combustion can only occur if the air and fuel is present in the

exact stoichiometric ratio, which allows all the carbon and hydrogen from the fuel

to combine with all the oxygen in the air, with no undesirable polluting

leftovers. Oxygen sensors monitor the amount of oxygen in the exhaust, and the

ECU uses this information to adjust the air-to-fuel ratio in real-time.

To achieve stoichiometry, the air mass flow into the engine is measured and

multiplied by the stoichiometric air/fuel ratio 14.64:1 (by weight) for gasoline. The

required fuel mass that must be injected into the engine is then translated to the

required pulse width for the fuel injector. The stoichiometric ratio changes as a

function of the fuel; diesel, gasoline, ethanol, methanol, propane, methane (natural

gas), or hydrogen.

Deviations from stoichiometry are required during non-standard operating

conditions such as heavy load, or cold operation, in which case, the mixture ratio

can range from 10:1 to 18:1 (for gasoline). In early fuel injection systems this was

accomplished with a thermotime switch.

Pulse width is inversely related to pressure difference across the injector inlet and

outlet. For example, if the fuel line pressure increases (injector inlet), or the

manifold pressure decreases (injector outlet), a smaller pulse width will admit the

same fuel. Fuel injectors are available in various sizes and spray characteristics as

well. Compensation for these and many other factors are programmed into the

ECU's software.

Various injection schemes

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Single-point injection

Single-point injection, called Throttle-body injection (TBI) by General

Motors and Central Fuel Injection (CFI) by Ford, was introduced in the 1940s in

large aircraft engines (then called thepressure carburetor) and in the 1980s in the

automotive world. The SPI system injects fuel at the throttle body (the same location

where a carburetor introduced fuel). The induction mixture passes through the intake

runners like a carburetor system, and is thus labelled a "wet manifold system". Fuel

pressure is usually specified to be in the area of 10-15 psi. The justification for single-

point injection was low cost. Many of the carburetor's supporting components could be

reused such as the air cleaner, intake manifold, and fuel line routing. This postponed

the redesign and tooling costs of these components. Most of these components were

later redesigned for the next phase of fuel injection's evolution, which is individual port

injection, commonly known as MPFI or "multi-point fuel injection". TBI was used

extensively on American-made passenger cars and light trucks in the 1980-1995

timeframe and some transition-engined European cars throughout the early and mid-

1990s. Mazda called their system EGI, and even introduced an electronically

controlled version called the EGI-S.

Continuous injection

In a continuous injection system, fuel flows at all times from the fuel injectors, but at a

variable flow rate. This is in contrast to most fuel injection systems, which provide fuel

during short pulses of varying duration, with a constant rate of flow during each pulse.

Continuous injection systems can be multi-point or single-point, but not direct.

The most common automotive continuous injection system is Bosch's K-Jetronic (K

for kontinuierlich, German for "continuous" — a.k.a. CIS — Continuous Injection

System), introduced in 1974. Gasoline is pumped from the fuel tank to a large control

valve called a fuel distributor, which separates the single fuel supply pipe from the

tank into smaller pipes, one for each injector. The fuel distributor is mounted atop a

control vane through which all intake air must pass, and the system works by varying

fuel volume supplied to the injectors based on the angle of the air vane, which in turn

is determined by the volume flowrate of air past the vane, and by the control pressure.

The control pressure is regulated with a mechanical device called the control pressure

regulator (CPR) or the warm-up regulator (WUR). Depending on the model, the CPR

may be used to compensate for altitude, full load, and/or a cold engine. On cars

equipped with an oxygen sensor, the fuel mixture is adjusted by a device called the

frequency valve. The injectors are simple spring-loaded check valves with nozzles;

once fuel system pressure becomes high enough to overcome the counterspring, the

injectors begin spraying. K-Jetronic was used for many years between 1974 and the

mid 1990s by BMW, Lamborghini, Ferrari, Mercedes-

Benz, Volkswagen, Ford, Porsche, Audi, Saab, DeLorean, andVolvo. There was also

a variant of the system called KE-Jetronic with electronic instead of mechanical

control of the control pressure. Some Toyotas and other Japanese cars from the

1970s to the early 1990s used an application of Bosch's multipoint L-Jetronic system

manufactured under license by DENSO. Chrysler used a similar continuous fuel

injection system on the 1981-1983 Imperial.

In piston aircraft engines, continuous-flow fuel injection is the most common type. In

contrast to automotive fuel injection systems, aircraft continuous flow fuel injection is

all mechanical, requiring no electricity to operate. Two common types exist: the

Bendix RSA system, and the TCM system. The Bendix system is a direct descendant

of the pressure carburetor. However, instead of having a discharge valve in the barrel,

it uses a flow divider mounted on top of the engine, which controls the discharge rate

and evenly distributes the fuel to stainless steel injection lines which go to the intake

ports of each cylinder. The TCM system is even more simple. It has no venturi, no

pressure chambers, no diaphragms, and no discharge valve. The control unit is fed by

a constant-pressure fuel pump. The control unit simply uses a butterfly valve for the

air which is linked by a mechanical linkage to a rotary valve for the fuel. Inside the

control unit is another restriction which is used to control the fuel mixture. The

pressure drop across the restrictions in the control unit controls the amount of fuel

flowing, so that fuel flow is directly proportional to the pressure at the flow divider. In

fact, most aircraft using the TCM fuel injection system feature a fuel flow gauge which

is actually a pressure gauge that has been calibrated in gallons per hour or pounds

per hour of fuel.

Central port injection (CPI)

General Motors implemented a system called "central port injection" (CPI) or "central

port fuel injection" (CPFI). It uses tubes with poppet valves from a central injector to

spray fuel at each intake port rather than the central throttle-body[citation needed]. Pressure

specifications typically mirror that of a TBI system. The two variants were CPFI from

1992 to 1995, and CSFI from 1996 and on[citation needed]. CPFI is a batch-fire system, in

which fuel is injected to all ports simultaneously. The 1996 and later CSFI system

sprays fuel sequentially.[22]

Multi-point fuel injection

Multi-point fuel injection injects fuel into the intake ports just upstream of each

cylinder's intake valve, rather than at a central point within an intake manifold. MPFI

(or just MPI) systems can besequential, in which injection is timed to coincide with

each cylinder's intake stroke; batched, in which fuel is injected to the cylinders in

groups, without precise synchronization to any particular cylinder's intake stroke;

or simultaneous, in which fuel is injected at the same time to all the cylinders. The

intake is only slightly wet, and typical fuel pressure runs between 40-60 psi.

Many modern EFI systems utilize sequential MPFI; however, in newer gasoline

engines, direct injection systems are beginning to replace sequential ones.

Direct injection

Direct fuel injection costs more than indirect injection systems: the injectors are

exposed to more heat and pressure, so more costly materials and higher-precision

electronic management systems are required. However, the entire intake is dry,

making this a very clean system. In a common rail system, the fuel from the fuel tank

is supplied to the common header (called the accumulator). This fuel is then sent

through tubing to the injectors which inject it into the combustion chamber. The

header has a high pressure relief valve to maintain the pressure in the header and

return the excess fuel to the fuel tank. The fuel is sprayed with the help of a nozzle

which is opened and closed with a needle valve, operated with a solenoid. When the

solenoid is not activated, the spring forces the needle valve into the nozzle passage

and prevents the injection of fuel into the cylinder. The solenoid lifts the needle valve

from the valve seat, and fuel under pressure is sent in the engine cylinder. Third-

generation common rail diesels use piezoelectric injectors for increased precision,

with fuel pressures up to 1,800 bar/26,000 psi.

Gasoline engines incorporate gasoline direct injection engine technology.

Diesel engines

Diesel engines must use fuel injection, and it must be timed (unlike on petrol engines).

Throughout the early history of diesels, they were always fed by a mechanical pump

with a small separate cylinder for each cylinder, feeding separate fuel lines and

individual injectors. Most such pumps were in-line, though some were rotary.

Earlier systems, relying on crude injectors, often injected into a sub-chamber shaped

to swirl the compressed air and improve combustion; this was known as indirect

injection. However, it was less thermally efficient than the now universal direct

injection in which initiation of combustion takes place in a depression (often toroidal)

in the crown of the piston.

Petrol/gasoline engines

Main article: gasoline direct injection

Modern petrol engines (gasoline engines) also utilise direct injection, which is referred

to as gasoline direct injection. This is the next step in evolution from multi-point fuel

injection, and offers another magnitude of emission control by eliminating the "wet"

portion of the induction system along the inlet tract.

By virtue of better dispersion and homogeneity of the directly injected fuel, the cylinder

and piston are cooled, thereby permitting higher compression ratios and more

aggressive ignition timing, with resultant enhanced power output. More precise

management of the fuel injection event also enables better control of emissions.

Finally, the homogeneity of the fuel mixture allows for leaner air/fuel ratios, which

together with more precise ignition timing can improve fuel efficiency. Along with this,

the engine can operate with stratified (lean burn) mixtures, and hence avoid throttling

losses at low and part engine load. Some direct-injection systems

incorporate piezoelectronic fuel injectors. With their extremely fast response time,

multiple injection events can occur during each cycle of each cylinder of the engine.

The first use of direct petrol injection was on the Hesselman engine, invented by

Swedish engineer Jonas Hesselman in 1925.[23][24]

Maintenance hazards

Fuel injection introduces potential hazards in engine maintenance due to the high fuel

pressures used. Residual pressure can remain in the fuel lines long after an injection-

equipped engine has been shut down. This residual pressure must be relieved, and if

it is done so by external bleed-off, the fuel must be safely contained. If a high-

pressure diesel fuel injector is removed from its seat and operated in open air, there is

a risk to the operator of injury by hypodermic jet-injection, even with only 100 psi

(6.9 bar) pressure.[25] The first known such injury occurred in 1937 during a diesel

engine maintenance operation.[26]

Diesel Fuel Injection System

The diesel internal combustion engine differs from the gasoline powered Otto cycle by

using highly compressed hot air to ignite the fuel rather than using a spark plug

(compression ignition rather than spark ignition).

In the true diesel engine, only air is initially introduced into the combustion chamber.

The air is then compressed with a compression ratio typically between 15:1 and 22:1

resulting in 40-bar (4.0 MPa; 580 psi) pressure compared to 8 to 14 bars (0.80 to 1.4

MPa) (about 200 psi) in the petrol engine. This high compression heats the air to 550

°C (1,022 °F). At about the top of the compression stroke, fuel is injected directly into

the compressed air in the combustion chamber. This may be into a (typically toroidal)

void in the top of the piston or a pre-chamber depending upon the design of the

engine. The fuel injector ensures that the fuel is broken down into small droplets, and

that the fuel is distributed evenly. The heat of the compressed air vaporizes fuel from

the surface of the droplets. The vapour is then ignited by the heat from the

compressed air in the combustion chamber, the droplets continue to vaporise from

their surfaces and burn, getting smaller, until all the fuel in the droplets has been

burnt. The start of vaporisation causes a delay period during ignition and the

characteristic diesel knocking sound as the vapour reaches ignition temperature and

causes an abrupt increase in pressure above the piston. The rapid expansion of

combustion gases then drives the piston downward, supplying power to the

crankshaft.[23] Engines for scale-model aeroplanes use a variant of the Diesel principle

but premix fuel and air via a carburation system external to the combustion chambers.

As well as the high level of compression allowing combustion to take place without a

separate ignition system, a high compression ratio greatly increases the engine's

efficiency. Increasing the compression ratio in a spark-ignition engine where fuel and

air are mixed before entry to the cylinder is limited by the need to prevent

damaging pre-ignition. Since only air is compressed in a diesel engine, and fuel is not

introduced into the cylinder until shortly before top dead centre (TDC), premature

detonation is not an issue and compression ratios are much higher.

[edit]Early fuel injection systems

Diesel's original engine injected fuel with the assistance of compressed air, which

atomized the fuel and forced it into the engine through a nozzle (a similar principle to

an aerosol spray). The nozzle opening was closed by a pin valve lifted by the

camshaft to initiate the fuel injection before top dead centre (TDC). This is called an

air-blast injection. Driving the three stage compressor used some power but the

efficiency and net power output was more than any other combustion engine at that

time.

Diesel engines in service today raise the fuel to extreme pressures by mechanical

pumps and deliver it to the combustion chamber by pressure-activated injectors

without compressed air. With direct injected diesels, injectors spray fuel through 4 to

12 small orifices in its nozzle. The early air injection diesels always had a superior

combustion without the sharp increase in pressure during combustion. Research is

now being performed and patents are being taken out to again use some form of air

injection to reduce the nitrogen oxides and pollution, reverting to Diesel's original

implementation with its superior combustion and possibly quieter operation. In all

major aspects, the modern diesel engine holds true to Rudolf Diesel's original design,

that of igniting fuel by compression at an extremely high pressure within the cylinder.

With much higher pressures and high technology injectors, present-day diesel

engines use the so-called solid injection system applied by Herbert Akroyd Stuart for

his hot bulb engine. The indirect injection engine could be considered the latest

development of these low speed hot bulb ignition engines..

[edit]Fuel delivery

A vital component of all diesel engines is a mechanical or electronic governor which

regulates the idling speed and maximum speed of the engine by controlling the rate of

fuel delivery. Unlike Otto-cycle engines, incoming air is not throttled and a diesel

engine without a governor cannot have a stable idling speed and can easily

overspeed, resulting in its destruction. Mechanically governed fuel injection systems

are driven by the engine's gear train.[24] These systems use a combination of springs

and weights to control fuel delivery relative to both load and speed.[24] Modern

electronically controlled diesel engines control fuel delivery by use of an electronic

control module (ECM) or electronic control unit (ECU). The ECM/ECU receives an

engine speed signal, as well as other operating parameters such as intake manifold

pressure and fuel temperature, from a sensor and controls the amount of fuel and

start of injection timing through actuators to maximise power and efficiency and

minimise emissions. Controlling the timing of the start of injection of fuel into the

cylinder is a key to minimizing emissions, and maximizing fuel economy (efficiency),

of the engine. The timing is measured in degrees of crank angle of the piston before

top dead centre. For example, if the ECM/ECU initiates fuel injection when the piston

is 10 degrees before TDC, the start of injection, or timing, is said to be 10° BTDC.

Optimal timing will depend on the engine design as well as its speed and load.

Advancing the start of injection (injecting before the piston reaches to its SOI-TDC)

results in higher in-cylinder pressure and temperature, and higher efficiency, but also

results in elevated engine noise and increased oxides of nitrogen (NOx) emissions due

to higher combustion temperatures. Delaying start of injection causes incomplete

combustion, reduced fuel efficiency and an increase in exhaust smoke, containing a

considerable amount of particulate matter and unburned hydrocarbons.

[edit]Major advantages

Diesel engines have several advantages over other internal combustion engines:

They burn less fuel than a petrol engine performing the same work, due to the

engine's higher temperature of combustion and greater expansion ratio.[1] Gasoline

engines are typically 30 percent efficient while diesel engines can convert over 45

percent of the fuel energy into mechanical energy[25] (see Carnot cycle for further

explanation).

They have no high voltage electrical ignition system, resulting in high reliability

and easy adaptation to damp environments. The absence of coils, spark plug

wires, etc., also eliminates a source of radio frequency emissions which can

interfere with navigation and communication equipment, which is especially

important in marine and aircraft applications.

The life of a diesel engine is generally about twice as long as that of a petrol

engine[26] due to the increased strength of parts used. Diesel fuel has better

lubrication properties than petrol as well.

Bus powered by biodiesel

Diesel fuel  is distilled directly from petroleum. Distillation yields some gasoline,

but the yield would be inadequate without catalytic reforming, which is a more

costly process.

Diesel fuel is considered safer than petrol in many applications. Although diesel

fuel will burn in open air using a wick, it will not explode and does not release a

large amount of flammable vapor. The low vapor pressure of diesel is especially

advantageous in marine applications, where the accumulation of explosive fuel-air

mixtures is a particular hazard. For the same reason, diesel engines are immune

to vapor lock.

For any given partial load the fuel efficiency (mass burned per energy

produced) of a diesel engine remains nearly constant, as opposed to petrol and

turbine engines which use proportionally more fuel with partial power outputs.[27][28]

[29][30]

They generate less waste heat in cooling and exhaust.[1]

Diesel engines can accept super- or turbo-charging pressure without any

natural limit, constrained only by the strength of engine components. This is unlike

petrol engines, which inevitably suffer detonation at higher pressure.

The carbon monoxide content of the exhaust is minimal, therefore diesel

engines are used in underground mines.[31]

Biodiesel  is an easily synthesized, non-petroleum-based fuel

(through transesterification) which can run directly in many diesel engines, while

gasoline engines either need adaptation to runsynthetic fuels or else use them as

an additive to gasoline (e.g., ethanol added to gasohol).

[edit]Mechanical and electronic injection

Many configurations of fuel injection have been used over the past century (1901–

2000).

Most present day (2008) diesel engines make use of a camshaft, rotating at half

crankshaft speed, lifted mechanical single plunger high-pressure fuel pump driven by

the engine crankshaft. For each engine cylinder, the corresponding plunger in the fuel

pump measures out the correct amount of fuel and determines the timing of each

injection. These engines use injectors that are very precise spring-loaded valves that

open and close at a specific fuel pressure. Separate high-pressure fuel lines connect

the fuel pump with each cylinder. Fuel volume for each single combustion is controlled

by a slanted groove in the plunger which rotates only a few degrees releasing the

pressure and is controlled by a mechanical governor, consisting of weights rotating at

engine speed constrained by springs and a lever. The injectors are held open by the

fuel pressure. On high-speed engines the plunger pumps are together in one unit.[32] The length of fuel lines from the pump to each injector is normally the same for

each cylinder in order to obtain the same pressure delay.

A cheaper configuration on high-speed engines with fewer than six cylinders is to use

an axial-piston distributor pump, consisting of one rotating pump plunger delivering

fuel to a valve and line for each cylinder (functionally analogous to points and

distributor cap on an Otto engine).[24]

Many modern systems have a single fuel pump which supplies fuel constantly at high

pressure with a common rail (single fuel line common) to each injector. Each injector

has a solenoid operated by an electronic control unit, resulting in more accurate

control of injector opening times that depend on other control conditions, such as

engine speed and loading, and providing better engine performance and fuel

economy. This design is also mechanically simpler than the combined pump and

valve design, making it generally more reliable, and less loud, than its mechanical

counterpart.[citation needed] This system does have have the drawback of requiring a

reliable electrical system for operation.

Both mechanical and electronic injection systems can be used in

either direct or indirect injection configurations.

Older diesel engines with mechanical injection pumps could be inadvertently run in

reverse, albeit very inefficiently. When this occurs, massive amounts of soot are

ejected from the air intake. This was often a consequence of push starting a vehicle

using the wrong gear. Large ship diesels are capable of running either direction.

[edit]Indirect injectionMain article: Indirect injection

An indirect injection diesel engine delivers fuel into a chamber off the combustion

chamber, called a pre-chamber or ante-chamber, where combustion begins and then

spreads into the main combustion chamber, assisted by turbulence created in the

chamber. This system allows for a smoother, quieter running engine, and because

combustion is assisted by turbulence, injector pressures can be lower, about 100 bar

(10 MPa; 1,500 psi), using a single orifice tapered jet injector. Mechanical injection

systems allowed high-speed running suitable for road vehicles (typically up to speeds

of around 4,000 rpm). The pre-chamber had the disadvantage of increasing heat loss

to the engine's cooling system, and restricting the combustion burn, which reduced

the efficiency by 5–10 percent.[33] Indirect injection engines were used in small-

capacity, high-speed diesel engines in automotive, marine and construction uses from

the 1950s, until direct injection technology advanced in the 1980s[citation needed]. Indirect

injection engines are cheaper to build and it is easier to produce smooth, quiet-

running vehicles with a simple mechanical system. In road-going vehicles most prefer

the greater efficiency and better controlled emission levels of direct injection. Indirect

injection diesels can still be found in the many ATV diesel applications.

[edit]Direct injection

Direct injection diesel engines have injectors mounted at the top of the combustion

chamber. The injectors are activated using one of two methods - hydraulic pressure

from the fuel pump, or an electonic signal from an engine controller.

Hydraulic pressure activated injectors can produce harsh engine noise. Fuel

consumption was about 15 to 20 percent lower than indirect injection diesels. The

extra noise was generally not a problem for industrial uses of the engine. But for

automotive usage, buyers had to decide whether or not the increased fuel efficiency

would compensate for the extra noise.

Electronic control of the fuel injection transformed the direct injection engine. This was

pioneered by Fiat in 1986 (Croma). The injection pressure remained around 300 bar

(30 MPa; 4,400 psi), but the injection timing fuel quantity, EGR, and turbo boost are all

electronically controlled. This gives more precise control of these parameters,

resulting in lowered emissions and quieter, smoother running engines.[citation needed]

[edit]Unit direct injectionMain article: Unit Injector

Unit direct injection also injects fuel directly into the cylinder of the engine. In this

system the injector and the pump are combined into one unit positioned over each

cylinder controlled by the camshaft. Each cylinder has its own unit eliminating the

high-pressure fuel lines, achieving a more consistent injection. This type of injection

system, also developed by Bosch, is used by Volkswagen AG in cars (where it is

called a Pumpe-Düse-System—literally pump-nozzle system) and by Mercedes Benz

("PLD") and most major diesel engine manufacturers in large commercial engines

(CAT, Cummins,Detroit Diesel, Volvo). With recent advancements, the pump pressure

has been raised to 2,400 bar (240 MPa; 35,000 psi),[34] allowing injection parameters

similar to common rail systems.[35]

[edit]Common rail direct injectionMain article: Common rail

In common rail systems, the separate pulsing high-pressure fuel line to each cylinder's

injector is also eliminated. Instead, a high-pressure pump pressurizes fuel at up to

2,500 bar (250 MPa; 36,000 psi),[36] in a "common rail". The common rail is a tube that

supplies each computer-controlled injector containing a precision-machined nozzle

and a plunger driven by a solenoid or piezoelectricactuator.

[edit]Cold weather[edit]Starting

In cold weather, high speed diesel engines can be difficult to start because the mass

of the cylinder block and cylinder head absorb the heat of compression, preventing

ignition due to the higher surface-to-volume ratio. Pre-chambered engines make use

of small electric heaters inside the pre-chambers called glowplugs, while the direct-

injected engines have these glowplugs in the combustion chamber. These engines

also generally have a higher compression ratio of 19:1 to 21:1. Low-speed and

compressed-air-started larger and intermediate-speed diesels do not have glowplugs

and compression ratios are around 16:1.[citation needed]

Some engines (e.g., some Cummins models) use resistive grid heaters in the intake

manifold to warm the inlet air until the engine reaches operating temperature. Engine

block heaters (electric resistive heaters in the engine block) connected to the utility

grid are often used when an engine is turned off for extended periods (more than an

hour) in cold weather to reduce startup time and engine wear. Block heaters are also

used for emergency power standby Diesel-powered generators which must rapidly

pick up load on a power failure. In the past, a wider variety of cold-start methods were

used. Some engines, such as Detroit Diesel [37]  engines and Lister-Petter engines,

used[when?] a system to introduce small amounts of ether into the inlet manifold to start

combustion.[citation needed]Saab-Scania marine engines, Field Marshall tractors (among

others) used slow-burning solid-fuel 'cigarettes' which were fitted into the cylinder

head as a primitive glow plug.[citation needed]

Lucas developed the Thermostart, where an electrical heating element was combined

with a small fuel valve in the inlet manifold. Diesel fuel slowly dripped from the valve

onto the hot element and ignited. The flame heated the inlet manifold and when the

engine was cranked, the flame was drawn into the cylinders to start combustion.[citation

needed]

International Harvester developed a tractor in the 1930s that had a 7-litre 4-cylinder

engine which started as a gasoline engine and ran on diesel after warming up. The

cylinder head had valves which opened for a portion of the compression stroke to

reduce the effective compression ratio, and a magneto produced the spark. An

automatic ratchet system automatically disengaged the ignition system and closed the

valves once the engine had run for 30 seconds. The operator then switched off the

petrol fuel system and opened the throttle on the diesel injection system.[citation needed]

Recent direct-injection systems[which?] are advanced to the extent that pre-chambers

systems are not needed by using a common rail fuel system with electronic fuel

injection.[citation needed]

[edit]Gelling

Diesel fuel is also prone to waxing or gelling in cold weather; both are terms for the

solidification of diesel oil into a partially crystalline state. The crystals build up in the

fuel line (especially in fuel filters), eventually starving the engine of fuel and causing it

to stop running. Low-output electric heaters in fuel tanks and around fuel lines are

used to solve this problem. Also, most engines have a spill return system, by which

any excess fuel from the injector pump and injectors is returned to the fuel tank. Once

the engine has warmed, returning warm fuel prevents waxing in the tank. Due to

improvements in fuel technology with additives, waxing rarely occurs in all but the

coldest weather when a mix of diesel and kerosene should be used to run a vehicle.

[edit]Types

[edit]Size Groups

Two Cycle Diesel engine with Roots blower, typical of Locomotive Engines

There are three size groups of Diesel engines[38]

Small - Under 188 kW output

Medium

Large

[edit]Basic Types of Diesel Engines

There are two basic types of Diesel Engines[38]

Four Cycle

Two Cycle

[edit]Early

Rudolf Diesel based his engine on the design of the Gas engine created by Nikolaus

Otto in 1876 with the goal of improving its efficiency. He patented his Diesel engine

concepts in patents that were set forth in 1892 and 1893.[39] As such, diesel engines in

the late 19th and early 20th centuries used the same basic layout and form as

industrial steam engines, with long-bore cylinders, external valve gear, cross-head

bearings and an open crankshaft connected to a large flywheel.[dubious – discuss] Smaller

engines would be built with vertical cylinders, while most medium- and large-sized

industrial engines were built with horizontal cylinders, just as steam engines had

been. Engines could be built with more than one cylinder in both cases. The largest

early diesels resembled the triple-expansion steam reciprocating engine, being tens of

feet high with vertical cylinders arranged in-line. These early engines ran at very slow

speeds—partly due to the limitations of their air-blast injector equipment and partly so

they would be compatible with the majority of industrial equipment designed for steam

engines; maximum speeds of between 100 and 300 rpm were common. Engines were

usually started by allowing compressed air into the cylinders to turn the engine,

although smaller engines could be started by hand.[40]

In 1897 when the first Diesel engine was completed Adolphus Busch traveled to

Cologne and negotiated exclusive right to produce the Diesel engine in the USA and

Canada. In his examination of the engine it was noted that the Diesel at that time

operated at efficiencies of 32 to 35 percent thermodynamic efficiency when a typical

triple expansion steam engine would operate at about 18 percent.[10]

In the early decades of the 20th century, when large diesel engines were first being

used, the engines took a form similar to the compound steam engines common at the

time, with the piston being connected to the connecting rod by a crosshead bearing.

Following steam engine practice some manufactures made double-acting two-stroke

and four-stroke diesel engines to increase power output, with combustion taking place

on both sides of the piston, with two sets of valve gear and fuel injection. While it

produced large amounts of power and was very efficient, the double-acting diesel

engine's main problem was producing a good seal where the piston rod passed

through the bottom of the lower combustion chamber to the crosshead bearing, and

no more were built. By the 1930s turbochargers were fitted to some engines.

Crosshead bearings are still used to reduce the wear on the cylinders in large long-

stroke main marine engines.

[edit]Modern

A Yanmar 2GM20 marine diesel engine, installed in a sailboat

As with petrol engines, there are two classes of diesel engines in current use: two-

stroke and four-stroke. The four-stroke type is the "classic" version, tracing its lineage

back to Rudolf Diesel's prototype. It is also the most commonly used form, being the

preferred power source for many motor vehicles, especially buses and trucks. Much

larger engines, such as used for railroad locomotion and marine propulsion, are often

two-stroke units, offering a more favourablepower-to-weight ratio, as well as better

fuel economy. The most powerful engines in the world are two-stroke diesels of

mammoth dimensions.[41]

Two-stroke diesel engine operation is similar to that of petrol counterparts, except that

fuel is not mixed with air before induction, and the crankcase does not take an active

role in the cycle. The traditional two-stroke design relies upon a mechanically

driven positive displacement blower to charge the cylinders with air before

compression and ignition. The charging process also assists in expelling

(scavenging) combustion gases remaining from the previous power stroke.

The archetype of the modern form of the two-stroke diesel is the Detroit

Diesel engine, in which the blower pressurizes a chamber in the engine block that is

often referred to as the "air box". The (much larger) Electro-Motive prime mover used

in EMD diesel-electric locomotives is built to the same principle.

In a two-stroke diesel engine, as the cylinder's piston approaches the bottom dead

centre exhaust ports or valves are opened relieving most of the excess pressure after

which a passage between the air box and the cylinder is opened, permitting air flow

into the cylinder.[42][43] The air flow blows the remaining combustion gases from the

cylinder—this is the scavenging process. As the piston passes through bottom centre

and starts upward, the passage is closed and compression commences, culminating

in fuel injection and ignition. Refer to two-stroke diesel engines for more detailed

coverage of aspiration types and supercharging of two-stroke diesel engines.

Normally, the number of cylinders are used in multiples of two, although any number

of cylinders can be used as long as the load on the crankshaft is counterbalanced to

prevent excessive vibration. The inline-six-cylinder design is the most prolific in light-

to medium-duty engines, though small V8 and larger inline-four displacement engines

are also common. Small-capacity engines (generally considered to be those below

five litres in capacity) are generally four- or six-cylinder types, with the four-cylinder

being the most common type found in automotive uses. Five-cylinder diesel engines

have also been produced, being a compromise between the smooth running of the

six-cylinder and the space-efficient dimensions of the four-cylinder. Diesel engines for

smaller plant machinery, boats, tractors, generators and pumps may be four-, three-

or two-cylinder types, with the single-cylinder diesel engine remaining for light

stationary work. Direct reversible two-stroke marine diesels need at least three

cylinders for reliable restarting forwards and reverse, while four-stroke diesels need at

least six cylinders.

The desire to improve the diesel engine's power-to-weight ratio produced several

novel cylinder arrangements to extract more power from a given capacity. The

uniflow opposed-piston engine uses two pistons in one cylinder with the combustion

cavity in the middle and gas in- and outlets at the ends. This makes a comparatively

light, powerful, swiftly running and economic engine suitable for use in aviation. An

example is the Junkers Jumo 204/205. The Napier Deltic engine, with three cylinders

arranged in a triangular formation, each containing two opposed pistons, the whole

engine having three crankshafts, is one of the better known.

[edit]Low-speed diesels

Low-speed diesel engines (as used in ships and other applications where overall

engine weight is relatively unimportant) often have a thermal efficiency which exceeds

50 percent.[1][2]

[edit]Gas generatorMain article: Free-piston engine

Before 1950, Sulzer started experimenting with two-stroke engines with boost

pressures as high as 6 atmospheres, in which all the output power was taken from an

exhaust gas turbine. The two-stroke pistons directly drove air compressor pistons to

make a positive displacement gas generator. Opposed pistons were connected by

linkages instead of crankshafts. Several of these units could be connected to provide

power gas to one large output turbine. The overall thermal efficiency was roughly

twice that of a simple gas turbine.[44] This system was derived from Raúl Pateras

Pescara's work on free-piston engines in the 1930s.

[edit]Advantages and disadvantages versus spark-ignition engines

This section needs additional citations for verification. Please help improve

this article by adding citations to reliable sources. Unsourced material may

be challenged and removed. (February 2011)

[edit]Power and fuel economy

The MAN S80ME-C7 low speed diesel engines use 155 gram fuel per kWh for an

overall energy conversion efficiency of 54.4 percent, which is the highest conversion

of fuel into power by any internal orexternal combustion engine.[1] Diesel engines are

more efficient than gasoline (petrol) engines of the same power rating, resulting in

lower fuel consumption. A common margin is 40 percent more miles per gallon for an

efficient turbodiesel. For example, the current model Škoda Octavia,

using Volkswagen Group engines, has a combined Euro rating of 6.2 L/100 km

(38 miles per US gallon, 16 km/L) for the 102 bhp (76 kW) petrol engine and

4.4 L/100 km (54 mpg, 23 km/L) for the 105 bhp (78 kW) diesel engine.

However, such a comparison does not take into account that diesel fuel is denser and

contains about 15 percent more energy by volume. Although the calorific value of the

fuel is slightly lower at 45.3 MJ/kg (megajoules per kilogram) than petrol at

45.8 MJ/kg, liquid diesel fuel is significantly denser than liquid petrol. This is significant

because volume of fuel, in addition to mass, is an important consideration in mobile

applications. No vehicle has an unlimited volume available for fuel storage.

Adjusting the numbers to account for the energy density of diesel fuel, the overall

energy efficiency is still about 20 percent greater for the diesel version.

While a higher compression ratio is helpful in raising efficiency, diesel engines are

much more efficient than gasoline (petrol) engines when at low power and at engine

idle. Unlike the petrol engine, diesels lack a butterfly valve (throttle) in the inlet

system, which closes at idle. This creates parasitic loss and destruction of availability

of the incoming air, reducing the efficiency of petrol engines at idle. In many

applications, such as marine, agriculture, and railways, diesels are left idling and

unattended for many hours, sometimes even days. These advantages are especially

attractive in locomotives (see dieselisation).

The average diesel engine has a poorer power-to-weight ratio than the petrol engine.

This is because the diesel must operate at lower engine speeds[45] and because it

needs heavier, stronger parts to resist the operating pressure caused by the high

compression ratio of the engine and the large amounts of torque generated to the

crankshaft. In addition, diesels are often built with stronger parts to give them longer

lives and better reliability, important considerations in industrial applications.

For most industrial or nautical applications, reliability is considered more important

than light weight and high power. Diesel fuel is injected just before the power stroke.

As a result, the fuel cannot burn completely unless it has a sufficient amount of

oxygen. This can result in incomplete combustion and black smoke in the exhaust if

more fuel is injected than there is air available for the combustion process. Modern

engines with electronic fuel delivery can adjust the timing and amount of fuel delivery

(by changing the duration of the injection pulse), and so operate with less waste of

fuel. In a mechanical system, the injection timing and duration must be set to be

efficient at the anticipated operating rpm and load, and so the settings are less than

ideal when the engine is running at any other RPM than what it is timed for. The

electronic injection can "sense" engine revs, load, even boost and temperature, and

continuously alter the timing to match the given situation. In the petrol engine, air and

fuel are mixed for the entire compression stroke, ensuring complete mixing even at

higher engine speeds.

Diesel engines usually have longer stroke lengths in order to achieve the necessary

compression ratios. As a result piston and connecting rods are heavier and more

force must be transmitted through the connecting rods and crankshaft to change the

momentum of the piston. This is another reason that a diesel engine must be stronger

for the same power output as a petrol engine.

Yet it is this characteristic that has allowed some enthusiasts to acquire significant

power increases with turbocharged engines by making fairly simple and inexpensive

modifications. A petrol engine of similar size cannot put out a comparable power

increase without extensive alterations because the stock components cannot

withstand the higher stresses placed upon them. Since a diesel engine is already built

to withstand higher levels of stress, it makes an ideal candidate for performance

tuning at little expense. However, it should be said that any modification that raises

the amount of fuel and air put through a diesel engine will increase its operating

temperature, which will reduce its life and increase service requirements. These are

issues with newer, lighter, high-performance diesel engines which are not "overbuilt"

to the degree of older engines and they are being pushed to provide greater power in

smaller engines. The addition of a turbocharger or supercharger to the engine greatly

assists in increasing fuel economy and power output, mitigating the fuel-air intake

speed limit mentioned above for a given engine displacement. Boost pressures can

be higher on diesels than on petrol engines, due to the latter's susceptibility to knock,

and the higher compression ratio allows a diesel engine to be more efficient than a

comparable spark ignition engine. Because the burned gases are expanded further in

a diesel engine cylinder, the exhaust gas is cooler, meaning turbochargers require

less cooling, and can be more reliable, than with spark-ignition engines.

With a diesel, boost pressure is essentially unlimited. It is literally possible to run as

much boost as the engine will physically stand before breaking apart.

The increased fuel economy of the diesel engine over the petrol engine means that

the diesel produces less carbon dioxide (CO2) per unit distance. Recent advances in

production and changes in the political climate have increased the availability and

awareness of biodiesel, an alternative to petroleum-derived diesel fuel with a much

lower net-sum emission of CO2, due to the absorption of CO2 by plants used to

produce the fuel. Although concerns are now being raised as to the negative effect

this is having on the world food supply, as the growing of crops specifically

for biofuels takes up land that could be used for food crops and uses water that could

be used by both humans and animals. However, the use of waste vegetable oil,

sawmill waste from managed forests in Finland, and advances in the production of

vegetable oil from algae demonstrate great promise in providing feed stocks for

sustainable biodiesel that are not in competition with food production.

Diesel engines have a lower rotational speed than an equivalent size petrol engine

because the diesel-air mixture burns slower than the petrol-air mixture.[citation needed] A

combination of improved mechanical technology (such as multi-stage injectors which

fire a short "pilot charge" of fuel into the cylinder to warm the combustion chamber

before delivering the main fuel charge), higher injection pressures that have improved

the atomisation of fuel into smaller droplets, and electronic control (which can adjust

the timing and length of the injection process to optimise it for all speeds and

temperatures) have mitigated most of these problems in the latest generation of

common-rail designs, while greatly improving engine efficiency. Poor power and

narrow torque bands have been addressed by superchargers, turbochargers,

(especially variable geometry turbochargers), intercoolers, and a large efficiency

increase from about 35 percent for IDI to 45 percent for the latest engines in the last

15 years.

Even though diesel engines have a theoretical fuel efficiency of 75 percent, in practice

it is lower. Engines in large diesel trucks, buses, and newer diesel cars can achieve

peak efficiencies around 45 percent,[46] and could reach 55 percent efficiency in the

near future.[47] However, average efficiency over a driving cycle is lower than peak

efficiency. For example, it might be 37 percent for an engine with a peak efficiency of

44 percent.[48]

[edit]EmissionsMain article: Diesel exhaust

In diesel engines, conditions in the engine differ from the spark-ignition engine, since

power is directly controlled by the fuel supply, rather than by controlling the air supply.

Thus when the engine runs at low power, there is enough oxygen present to burn the

fuel, and diesel engines only make significant amounts of carbon monoxide when

running under a load.

Diesel exhaust is well known for its characteristic smell; but in Britain this smell in

recent years has become much less because the sulfur is now removed from the fuel

in the oil refinery.

Diesel exhaust has been found to contain a long list of toxic air contaminants. Among

these pollutants, fine particle pollution is perhaps the most important as a cause

of diesel's harmful health effects.

[edit]Power and torque

For commercial uses requiring towing, load carrying and other tractive tasks, diesel

engines tend to have better torque characteristics. Diesel engines tend to have their

torque peak quite low in their speed range (usually between 1600 and 2000 rpm for a

small-capacity unit, lower for a larger engine used in a truck). This provides smoother

control over heavy loads when starting from rest, and, crucially, allows the diesel

engine to be given higher loads at low speeds than a petrol engine, making them

much more economical for these applications. This characteristic is not so desirable in

private cars, so most modern diesels used in such vehicles use electronic

control, variable geometry turbochargers and shorter piston strokes to achieve a wider

spread of torque over the engine's speed range, typically peaking at around 2500–

3000 rpm.

While diesel engines tend to have more torque at lower engine speeds than petrol

engines, diesel engines tend to have a narrower power band than petrol engines.

Naturally aspirated diesels tend to lack power and torque at the top of their speed

range. This narrow band is a reason why a vehicle such as a truck may have

a gearbox with as many as 18 or more gears, to allow the engine's power to be used

effectively at all speeds. Turbochargers tend to improve power at high engine speeds;

superchargers improve power at lower speeds; and variable geometry turbochargers

improve the engine's performance equally by flattening the torque curve.

[edit]Noise

The characteristic noise of a diesel engine is variably called diesel clatter, diesel

nailing, or diesel knock.[49] Diesel clatter is caused largely by the diesel combustion

process; the sudden ignition of the diesel fuel when injected into the combustion

chamber causes a pressure wave. Engine designers can reduce diesel clatter

through: indirect injection; pilot or pre-injection; injection timing; injection rate;

compression ratio; turbo boost; and exhaust gas recirculation (EGR).[50] Common rail

diesel injection systems permit multiple injection events as an aid to noise reduction.

Diesel fuels with a higher cetane rating modify the combustion process and reduce

diesel clatter.[49] CN (Cetane number) can be raised by distilling higher quality crude

oil, by catalyzing a higher quality product or by using a cetane improving additive.

Some oil companies market high cetane or premium diesel. Biodiesel has a higher

cetane number than petrodiesel, typically 55CN for 100% biodiesel.[citation needed]

A combination of improved mechanical technology such as multi-stage injectors which

fire a short "pilot charge" of fuel into the cylinder to initiate combustion before

delivering the main fuel charge, higher injection pressures that have improved the

atomisation of fuel into smaller droplets, and electronic control (which can adjust the

timing and length of the injection process to optimise it for all speeds and

temperatures), have partially mitigated these problems in the latest generation of

common-rail designs, while improving engine efficiency.

[edit]Reliability

The lack of an electrical ignition system greatly improves the reliability. The high

durability of a diesel engine is also due to its overbuilt nature (see above), a benefit

that is magnified by the lower rotating speeds in diesels. Diesel fuel is a better

lubricant than petrol so is less harmful to the oil film on piston

rings and cylinder bores; it is routine for diesel engines to cover 250,000 miles

(400,000 km) or more without a rebuild.

Due to the greater compression force required and the increased weight of the

stronger components, starting a diesel engine is harder. More torque is required to

push the engine through compression.

Either an electrical starter or an air-start system is used to start the engine turning. On

large engines, pre-lubrication and slow turning of an engine, as well as heating, are

required to minimise the amount of engine damage during initial start-up and running.

Some smaller military diesels can be started with an explosive cartridge, called

a Coffman starter, which provides the extra power required to get the machine turning.

In the past, Caterpillar and John Deere used a small petrol pony engine in their

tractors to start the primary diesel engine. The pony engine heated the diesel to aid in

ignition and used a small clutch and transmission to spin up the diesel engine. Even

more unusual was an International Harvester design in which the diesel engine had its

own carburetor and ignition system, and started on petrol. Once warmed up, the

operator moved two levers to switch the engine to diesel operation, and work could

begin. These engines had very complex cylinder heads, with their own petrol

combustion chambers, and were vulnerable to expensive damage if special care was

not taken (especially in letting the engine cool before turning it off).

[edit]Quality and variety of fuels

Petrol/gasoline engines are limited in the variety and quality of the fuels they can burn.

Older petrol engines fitted with a carburetor required a volatile fuel that would vaporise

easily to create the necessary air-fuel ratio for combustion. Because both air and fuel

are admitted to the cylinder, if the compression ratio of the engine is too high or the

fuel too volatile (with too low an octane rating), the fuel will ignite under compression,

as in a diesel engine, before the piston reaches the top of its stroke. This pre-ignition

causes a power loss and over time major damage to the piston and cylinder. The

need for a fuel that is volatile enough to vaporise but not too volatile (to avoid pre-

ignition) means that petrol engines will only run on a narrow range of fuels. There has

been some success at dual-fuel engines that use petrol and ethanol, petrol

and propane, and petrol and methane.

In diesel engines, a mechanical injector system vaporizes the fuel directly into the

combustion chamber or a pre-combustion chamber (as opposed to a Venturi jet in a

carburetor, or a fuel injector in a fuel injection system vaporising fuel into the intake

manifold or intake runners as in a petrol engine). This forced vaporisation means that

less-volatile fuels can be used. More crucially, because only air is inducted into the

cylinder in a diesel engine, the compression ratio can be much higher as there is no

risk of pre-ignition provided the injection process is accurately timed. This means that

cylinder temperatures are much higher in a diesel engine than a petrol engine,

allowing less volatile fuels to be used.

Diesel fuel is a form of light fuel oil, very similar to kerosene/paraffin, but diesel

engines, especially older or simple designs that lack precision electronic injection

systems, can run on a wide variety of other fuels. Some of the most common

alternatives are Jet A-1 type jet fuel or vegetable oil from a very wide variety of plants.

Some engines can be run on vegetable oil without modification, and most others

require fairly basic alterations. Biodiesel is a pure diesel-like fuel refined from

vegetable oil and can be used in nearly all diesel engines. Requirements for fuels to

be used in diesel engines are the ability of the fuel to flow along the fuel lines, the

ability of the fuel to lubricate the injector pump and injectors adequately, and its

ignition qualities (ignition delay, cetane number). Inline mechanical injector pumps

generally tolerate poor-quality or bio-fuels better than distributor-type pumps. Also,

indirect injection engines generally run more satisfactorily on bio-fuels than direct

injection engines. This is partly because an indirect injection engine has a much

greater 'swirl' effect, improving vaporisation and combustion of fuel, and because (in

the case of vegetable oil-type fuels) lipid depositions can condense on the cylinder

walls of a direct-injection engine if combustion temperatures are too low (such as

starting the engine from cold).

It is often reported that Diesel designed his engine to run on peanut oil. Diesel stated

in his published papers, "at the Paris Exhibition in 1900 (Exposition Universelle) there

was shown by the Otto Company a small diesel engine, which, at the request of the

French Government ran on Arachide (earth-nut or pea-nut) oil (see biodiesel), and

worked so smoothly that only a few people were aware of it. The engine was

constructed for using mineral oil, and was then worked on vegetable oil without any

alterations being made. The French Government at the time thought of testing the

applicability to power production of the Arachide, or earth-nut, which grows in

considerable quantities in their African colonies, and can easily be cultivated there."

Diesel himself later conducted related tests and appeared supportive of the idea.[51]

Most large marine diesels (sometimes called cathedral engines due to their size[citation

needed]) run on heavy fuel oil (sometimes called "bunker oil"), which is a thick, viscous

and almost flameproof fuel which is very safe to store and cheap to buy in bulk as it is

a waste product from the petroleum refining industry. The fuel must be heated to thin

it out (often by the exhaust header) and is often passed through multiple injection

stages to vaporise it.

[edit]Fuel and fluid characteristics

Main article: Diesel fuel

Diesel engines can operate on a variety of different fuels, depending on configuration,

though the eponymous diesel fuel derived from crude oil is most common. The

engines can work with the full spectrum of crude oil distillates, from natural gas,

alcohols, petrol, wood gas to the fuel oils from diesel oil to residual fuels.[52]

The type of fuel used is a combination of service requirements, and fuel costs. Good-

quality diesel fuel can be synthesised from vegetable oil and alcohol. Diesel fuel can

be made from coal or other carbon base using the Fischer-Tropsch

process. Biodiesel is growing in popularity since it can frequently be used in

unmodified engines, though production remains limited. Recently, biodiesel from

coconut, which can produce a very promising coco methyl ester (CME), has

characteristics which enhance lubricity and combustion giving a regular diesel engine

without any modification more power, less particulate matter or black smoke, and

smoother engine performance. The Philippines pioneers in the research on Coconut

based CME with the help of German and American scientists. Petroleum-derived

diesel is often called petrodiesel if there is need to distinguish the source of the fuel.

Pure plant oils are increasingly being used as a fuel for cars, trucks and

remote combined heat and power generation especially in Germany where hundreds

of decentralised small- and medium-sized oil presses cold press oilseed,

mainly rapeseed, for fuel. There is a Deutsches Institut für Normung fuel standard

for rapeseed oil fuel.

Residual fuels are the "dregs" of the distillation process and are a thicker, heavier oil,

or oil with higher viscosity, which are so thick that they are not readily pumpable

unless heated. Residual fuel oils are cheaper than clean, refined diesel oil, although

they are dirtier. Their main considerations are for use in ships and very large

generation sets, due to the cost of the large volume of fuel consumed, frequently

amounting to many tonnes per hour. The poorly refined biofuels straight vegetable

oil (SVO) and waste vegetable oil (WVO) can fall into this category, but can be viable

fuels on non common rail or TDI PD diesels with the simple conversion of fuel heating

to 80 to 100 degrees Celsius to reduce viscosity, and adequate filtration to OEM

standards. Engines using these heavy oils have to start and shut down on standard

diesel fuel, as these fuels will not flow through fuel lines at low temperatures. Moving

beyond that, use of low-grade fuels can lead to serious maintenance problems

because of their high sulphur and lower lubrication properties. Most diesel engines

that power ships like supertankers are built so that the engine can safely use low-

grade fuels due to their separate cylinder and crankcase lubrication.

Normal diesel fuel is more difficult to ignite and slower in developing fire than petrol

because of its higher flash point, but once burning, a diesel fire can be fierce.

Fuel contaminants such as dirt and water are often more problematic in diesel

engines than in petrol engines. Water can cause serious damage, due to corrosion, to

the injection pump and injectors; and dirt, even very fine particulate matter, can

damage the injection pumps due to the close tolerances that the pumps are machined

to. All diesel engines will have a fuel filter (usually much finer than a filter on a petrol

engine), and a water trap. The water trap (which is sometimes part of the fuel filter)

often has a float connected to a warning light, which warns when there is too much

water in the trap, and must be drained before damage to the engine can result. The

fuel filter must be replaced much more often on a diesel engine than on a petrol

engine, changing the fuel filter every 2-4 oil changes is not uncommon for some

vehicles.

[edit]Safety

[edit]Fuel flammability

Diesel fuel has low flammability, leading to a low risk of fire caused by fuel in a vehicle

equipped with a diesel engine.

In yachts diesels are used because petrol engines generate combustible vapors,

which can accumulate in the bottom of the vessel, sometimes causing explosions.

Therefore ventilation systems on petrol powered vessels are required.[53]

The United States Army and NATO use only diesel engines and turbines because of

fire hazard. Although neither gasoline nor diesel is explosive in liquid form, both can

create an explosive air/vapor mix under the right conditions. However, diesel fuel is

less prone due to its lower vapor pressure, which is an indication of evaporation rate.

The Material Safety Data Sheet[54] for ultra-low sulfur diesel fuel indicates a vapor

explosion hazard for diesel indoors, outdoors, or in sewers.

US Army gasoline-engined tanks during World War II were nicknamed Ronsons,

because of their greater likelihood of catching fire when damaged by enemy fire.

(Although tank fires were usually caused by detonation of the ammunition rather than

fuel.)

[edit]Maintenance hazards

Fuel injection introduces potential hazards in engine maintenance due to the high fuel

pressures used. Residual pressure can remain in the fuel lines long after an injection-

equipped engine has been shut down. This residual pressure must be relieved, and if

it is done so by external bleed-off, the fuel must be safely contained. If a high-

pressure diesel fuel injector is removed from its seat and operated in open air, there is

a risk to the operator of injury by hypodermic jet-injection, even with only

100 psi pressure.[55] The first known such injury occurred in 1937 during a diesel

engine maintenance operation.[56]

[edit]Diesel applications

The characteristics of diesel have different advantages for different applications.

[edit]Passenger cars

Diesel engines have long been popular in bigger cars and this is spreading to smaller

cars. Diesel engines tend to be more economical at regular driving speeds and are

much better at city speeds. Their reliability and life-span tend to be better (as

detailed). Some 40% or more of all cars sold in Europe are diesel-powered where

they are considered a low CO2 option. Mercedes-Benz in conjunction with Robert

Bosch GmbH produced diesel-powered passenger cars starting in 1936 and very

large numbers are used all over the world (often as "Grande Taxis" in the Third

World).

[edit]Railroad rolling stock

Diesel engines have eclipsed steam engines as the prime mover on all non-electrified

railroads in the industrialized world. The first diesel locomotives appeared in the early

20th century, and diesel multiple units soon after.

While electric locomotives have now replaced the diesel locomotive almost completely

on passenger traffic in Europe and Asia, diesel is still today very popular for cargo-

hauling freight trains and on tracks where electrification is not feasible.

Most modern diesel locomotives are actually diesel-electric locomotives: the diesel

engine is used to power an electric generator that in turn powers electric traction

engines with no mechanical connection between diesel engine and traction.

[edit]Other transport uses

Larger transport applications (trucks, buses, etc.) also benefit from the diesel's

reliability and high torque output. Diesel displaced paraffin (or tractor vaporising oil,

TVO) in most parts of the world by the end of the 1950s with the U.S. following some

20 years later.

Aircraft

Marine

Motorcycles

In merchant ships and boats, the same advantages apply with the relative safety of

diesel fuel an additional benefit. The German pocket battleships were the largest

diesel warships, but the German torpedo-boats known as E-boats (Schnellboot) of the

Second World War were also diesel craft. Conventional submarines have used them

since before the First World War, relying on the almost total absence of carbon

monoxide in the exhaust. American World War II diesel-electric submarines operated

on two-stroke cycle as opposed to the four-stroke cycle that other navies used.

[edit]Military fuel standardisation

NATO has a single vehicle fuel policy and has selected diesel for this purpose. The

use of a single fuel simplifies wartime logistics. NATO and the United States Marine

Corps have even been developing a diesel military motorcycle based on

a Kawasaki off road motorcycle, with a purpose designed naturally aspirated direct

injection diesel at Cranfield University in England, to be produced in the USA,

because motorcycles were the last remaining gasoline-powered vehicle in their

inventory. Before this, a few civilian motorcycles had been built using adapted

stationary diesel engines, but the weight and cost disadvantages generally

outweighed the efficiency gains.

[edit]Non-transport uses

A 1944 V12 2300 kW power plant undergoing testing & restoration works

Diesel engines are also used to power permanent, portable, and backup generators,

irrigation pumps,[57] corn grinders,[58] and coffee de-pulpers.[59]

[edit]Engine speeds

Within the diesel engine industry, engines are often categorized by their rotational

speeds into three unofficial groups:

High-speed engines,

medium-speed engines, and

slow-speed engines

High- and medium-speed engines are predominantly four-stroke engines; except for

the Detroit Diesel two-stroke range. Medium-speed engines are physically larger than

high-speed engines and can burn lower-grade (slower-burning) fuel than high-speed

engines. Slow-speed engines are predominantly large two-stroke crosshead engines,

hence very different from high- and medium-speed engines. Due to the lower

rotational speed of slow- and medium-speed engines, there is more time for

combustion during the power stroke of the cycle, allowing the use of slower-burning

fuels than high-speed engines.

[edit]High-speed engines

High-speed (approximately 1,000 rpm and greater) engines are used to

power trucks (lorries), buses, tractors, cars, yachts, compressors, pumps and

smallelectrical generators. As of 2008, most high-speed engines have direct injection.

Many modern engines, particularly in on-highway applications, have common

rail direct injection, which is cleaner burning.

[edit]Medium-speed engines

Medium-speed engines are used in large electrical generators, ship propulsion and

mechanical drive applications such as large compressors or pumps. Medium speed

diesel engines operate on either diesel fuel or heavy fuel oil by direct injection in the

same manner as low-speed engines.

Engines used in electrical generators run at approximately 300 to 1000 rpm and are

optimized to run at a set synchronous speed depending on the generation frequency

(50 or 60 hertz) and provide a rapid response to load changes. Typical synchronous

speeds for modern medium-speed engines are 500/514 rpm (50/60 Hz), 600 rpm

(both 50 and 60 Hz), 720/750 rpm, and 900/1000 rpm.

As of 2009, the largest medium-speed engines in current production have outputs up

to approximately 20 MW (27,000 hp). and are supplied by companies like MAN

B&W, Wärtsilä,[60] and Rolls-Royce (who acquired Ulstein Bergen Diesel in 1999).

Most medium-speed engines produced are four-stroke machines, however there are

some two-stroke medium-speed engines such as by EMD (Electro-Motive Diesel),

and the Fairbanks Morse OP (Opposed-piston engine) type.

Typical cylinder bore size for medium-speed engines ranges from 20 cm to 50 cm,

and engine configurations typically are offered ranging from in-line 4-cylinder units to

V-configuration 20-cylinder units. Most larger medium-speed engines are started with

compressed air direct on pistons, using an air distributor, as opposed to a pneumatic

starting motor acting on the flywheel, which tends to be used for smaller engines.

There is no definitive engine size cut-off point for this.

It should also be noted that most major manufacturers of medium-speed engines

make natural gas-fueled versions of their diesel engines, which in fact operate on

the Otto cycle, and require spark ignition, typically provided with a spark plug.[52] There

are also dual (diesel/natural gas/coal gas) fuel versions of medium and low speed

diesel engines using a lean fuel air mixture and a small injection of diesel fuel (so-

called "pilot fuel") for ignition. In case of a gas supply failure or maximum power

demand these engines will instantly switch back to full diesel fuel operation.[52][61][62]

[edit]Low-speed engines

The MAN B&W 5S50MC 5-cylinder, 2-stroke, low-speed marine diesel engine. This particular engine

is found aboard a 29,000 tonne chemical carrier.

Also known as slow-speed, or traditionally oil engines, the largest diesel engines are

primarily used to power ships, although there are a few land-based power generation

units as well. These extremely large two-stroke engines have power outputs up to

approximately 85 MW (114,000 hp), operate in the range from approximately 60 to

200 rpm and are up to 15 m (50 ft) tall, and can weigh over 2,000 short tons (1,800 t).

They typically use direct injection running on cheap low-grade heavy fuel, also known

as Bunker C fuel, which requires heating in the ship for tanking and before injection

due to the fuel's high viscosity. The heat for fuel heating is often provided by waste

heat recovery boilers located in the exhaust ducting of the engine, which produce the

steam required for fuel heating. Provided the heavy fuel system is kept warm and

circulating, engines can be started and stopped on heavy fuel.

Large and medium marine engines are started with compressed air directly applied to

the pistons. Air is applied to cylinders to start the engine forwards or backwards

because they are normally directly connected to the propeller without clutch or

gearbox, and to provide reverse propulsion either the engine must be run backwards

or the ship will utilise an adjustable propeller. At least three cylinders are required

with two-stroke engines and at least six cylinders withfour-stroke engines to

provide torque every 120 degrees.

Companies such as MAN B&W Diesel, (formerly Burmeister & Wain)

and Wärtsilä (which acquired Sulzer Diesel) design such large low-speed engines.

They are unusually narrow and tall due to the addition of a crosshead bearing. As of

2007, the 14-cylinder Wärtsilä-Sulzer 14RTFLEX96-C turbocharged two-stroke diesel

engine built by Wärtsilä licensee Doosan in Korea is the most powerful diesel engine

put into service, with a cylinder bore of 960 mm (37.8 in) delivering 114,800 hp

(85.6 MW). It was put into service in September 2006, aboard the world's largest

container ship Emma Maersk which belongs to the A.P. Moller-Maersk Group. Typical

bore size for low-speed engines ranges from approximately 35 to 98 cm (14 to 39 in).

As of 2008, all produced low-speed engines with crosshead bearings are in-line

configurations; no Vee versions have been produced.

[edit]Supercharging and turbocharging

Most diesels are now turbocharged and some are both turbo charged

and supercharged. Because diesels do not have fuel in the cylinder before

combustion is initiated, more than one bar (100 kPa) of air can be loaded in the

cylinder without preignition. A turbocharged engine can produce significantly more

power than a naturally aspirated engine of the same configuration, as having more air

in the cylinders allows more fuel to be burned and thus more power to be produced. A

supercharger is powered mechanically by the engine's crankshaft, while a

turbocharger is powered by the engine exhaust, not requiring any mechanical power.

Turbocharging can improve the fuel economy[63] of diesel engines by recovering waste

heat from the exhaust, increasing the excess air factor, and increasing the ratio of

engine output to friction losses.

A two-stroke engine does not have a discrete exhaust and intake stroke and thus is

incapable of self-aspiration. Therefore all two-stroke engines must be fitted with a

blower to charge the cylinders with air and assist in dispersing exhaust gases, a

process referred to as scavenging. In some cases, the engine may also be fitted with

a turbocharger, whose output is directed into the blower inlet. A few designs employ a

hybrid turbocharger for scavenging and charging the cylinders, which device is

mechanically driven at cranking and low speeds to act as a blower.

As turbocharged or supercharged engines produce more power for a given engine

size as compared to naturally aspirated engines, attention must be paid to the

mechanical design of components, lubrication, and cooling to handle the power.

Pistons are usually cooled with lubrication oil sprayed on the bottom of the piston.

Large engines may use water, sea water, or oil supplied throughtelescoping pipes

attached to the crosshead.

[edit]Current and future developments

See also: Diesel car history

As of 2008, many common rail and unit injection systems already employ new

injectors using stacked piezoelectric wafers in lieu of a solenoid, giving finer control of

the injection event.[64]

Variable geometry turbochargers have flexible vanes, which move and let more air

into the engine depending on load. This technology increases both performance and

fuel economy. Boost lag is reduced as turbo impeller inertia is compensated for.[65]

Accelerometer pilot control (APC) uses an accelerometer to provide feedback on the

engine's level of noise and vibration and thus instruct the ECU to inject the minimum

amount of fuel that will produce quiet combustion and still provide the required power

(especially while idling).[66]

The next generation of common rail diesels is expected to use variable injection

geometry, which allows the amount of fuel injected to be varied over a wider range,

and variable valve timing (see Mitsubishi's 4N13 diesel engine) similar to that

on petrol engines. Particularly in the United States, coming tougher emissions

regulations present a considerable challenge to diesel engine manufacturers.

Ford's HyTrans Project has developed a system which starts the ignition in 400 ms,

saving a significant amount of fuel on city routes, and there are other methods to

achieve even more efficient combustion, such as homogeneous charge compression

ignition, being studied.[67][68]

Lead–acid batteryFrom Wikipedia, the free encyclopedia

Lead–acid battery

lead acid car battery

specific energy 30–40 Wh/kg

energy density 60–75 Wh/l

specific power 180 W/kg

Charge/discharge efficiency 50%–92% [3]

Energy/consumer-price 7(sld)-18(fld) Wh/US$ [4]

Self-discharge rate 3–20%/month [5]

Cycle durability 500–800 cycles

Nominal cell voltage 2.105 V

Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable

battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, their ability to supply

high surge currents means that the cells maintain a relatively large power-to-weight ratio. These features, along with

their low cost, make them attractive for use in motor vehicles to provide the high current required by automobile

starter motors.

Lead–acid batteries (under 5 kg) account for 1.5% of all portable secondary battery sales in Japan by number of units

sold (25% by price).[1]Sealed lead–acid batteries accounted for 10% by weight of all portable battery sales in the EU in

2000. [2]

Electrochemistry

In the charged state, each cell contains negative electrodes of elemental lead (Pb)

and positive electrodes of lead(IV) oxide (PbO2) in an electrolyte of approximately

33.5% v/v (4.2 Molar) sulfuric acid(H2SO4).

In the discharged state both the positive and negative become lead(II) sulfate (PbSO4)

and the electrolyte loses much of its dissolved sulfuric acid and becomes primarily

water. Due to the freezing-point depression of water, as the battery discharges and

the concentration of sulfuric acid decreases, the electrolyte is more likely to freeze

during winter weather.

[edit]Discharge

Fully Discharged: Two identical lead sulfate plates

During discharge, both plates return to lead sulfate. The process is driven by the

conduction of electrons from the positive plate back into the cell at the negative plate.

Negative Plate Reaction: Pb(s) + HSO−

4(aq) → PbSO4(s) + 2e−

Positive Plate Reaction: PbO2(s) + HSO−

4(aq) + 4H+(aq) + 2e− → PbSO4(s) + 2H2O(l)

[edit]Recharging

Fully Charged: Lead and Lead Oxide plates

Subsequent charging places the battery back in its charged state, changing the

lead sulfates into lead and lead oxides. The process is driven by the forcible

removal of electrons from the negative plate and the forcible introduction of

them to the positive plate.

Negative Plate Reaction: PbSO4(s) + H+(aq) + 2e− → Pb(s) + HSO−

4(aq)Positive Plate Reaction: PbSO4(s) + 2H2O(l) → PbO2(s) + HSO−

4(aq) + 3H+(aq) + 2e−

Overcharging with high

charging voltages generates oxygen and hydrogen gas by electrolysis of

water, which is lost to the cell. Periodic maintenance of lead acid

batteries requires inspection of the electrolyte level and replacement of

any water that has been lost.

[edit]Voltages for common usages

These are general voltage ranges for six-cell lead-acid batteries:

Open-circuit (quiescent) at full charge: 12.6 V to 12.8 V (2.10–2.13V

per cell)

Open-circuit at full discharge: 11.8 V to 12.0 V

Loaded at full discharge: 10.5 V.

Continuous-preservation (float) charging: 13.4 V for gelled electrolyte;

13.5 V for AGM (absorbed glass mat) and 13.8 V for flooded cells

1. All voltages are at 20 °C (68 °F), and must be adjusted

−0.022V/°C for temperature changes.

2. Float voltage  recommendations vary, according to the

manufacturer's recommendation.

3. Precise float voltage (±0.05 V) is critical to longevity; insufficient

voltage (causes sulfation) which is almost as detrimental as

excessive voltage (causing corrosion and electrolyte loss)

Typical (daily) charging: 14.2 V to 14.5 V (depending on temperature

and manufacturer's recommendation)

Equalization charging (for flooded lead acids): 15 V for no more than

2 hours. Battery temperature must be monitored.

Gassing threshold: 14.4 V

After full charge, terminal voltage drops quickly to 13.2 V and then

slowly to 12.6 V.

Portable batteries, such as for miners' cap lamps (headlamps) typically

have two cells, and use one third of these voltages.[3]

[edit]Measuring the charge level

A hydrometer can be used to test the specific gravity of each cell as a measure of its

state of charge.

Because the electrolyte takes part in the charge-discharge reaction, this

battery has one major advantage over other chemistries. It is relatively

simple to determine the state of charge by merely measuring the specific

gravity (S.G.) of the electrolyte, the S.G. falling as the battery

discharges. Some battery designs include a simple hydrometer using

colored floating balls of differing density. When used in diesel-

electric submarines, the S.G. was regularly measured and written on a

blackboard in the control room to indicate how much longer the boat

could remain submerged.[4]

A battery's open-circuit voltage can be used to estimate the state of charge, in this

case for a 12-volt battery.[5]

[edit]Construction

[edit]Plates

The lead–acid cell can be demonstrated using sheet lead plates for the

two electrodes. However such a construction produces only around one

ampere for roughly postcard sized plates, and for only a few minutes.

Gaston Planté found a way to provide a much larger effective surface

area. In Planté's design, the positive and negative plates were formed of

two spirals of lead foil, separated with a sheet of cloth and coiled up. The

cells initially had low capacity, so a slow process of "forming" was

required to corrode the lead foils, creating lead dioxide on the plates and

roughening them to increase surface area. Initially this process used

electricity from primary batteries; when generators became available

after 1870, the cost of production of batteries greatly declined.[6] Planté

plates are still used in some stationary applications, where the plates are

mechanically grooved to increase their surface area.

Faure pasted-plate construction is typical of automotive batteries. Each

plate consists of a rectangular lead grid alloyed with antimony or calcium

to improve the mechanical characteristics. The holes of the grid are filled

with a paste of red lead and 33% dilute sulfuric acid. (Different

manufacturers vary the mixture). The paste is pressed into the holes in

the grid which are slightly tapered on both sides to better retain the

paste. This porous paste allows the acid to react with the lead inside the

plate, increasing the surface area many fold. Once dry, the plates are

stacked with suitable separators and inserted in the battery container. An

odd number of plates is usually used, with one more nagative plate than

positive. Each alternate plate is connected.

The positive plates are the chocolate brown color of Lead(IV) Oxide, and

the negative are the slate gray of "spongy" lead at the time of

manufacture. In this charged state the plates are called 'formed'.

One of the problems with the plates is that the plates increase in size as

the active material absorbs sulfate from the acid during discharge, and

decrease as they give up the sulfate during charging. This causes the

plates to gradually shed the paste. It is important that there is room

underneath the plates to catch this shed material. If it reaches the plates,

the cell short-circuits.

The paste contains carbon black, blanc fixe (barium sulfate)

and lignosulfonate. The blanc fixe acts as a seed crystal for the lead–to–

lead sulfate reaction. The blanc fixe must be fully dispersed in the paste

in order for it to be effective. The lignosulfonate prevents the negative

plate from forming a solid mass during the discharge cycle, instead

enabling the formation of long needle–like crystals. The long crystals

have more surface area and are easily converted back to the original

state on charging. Carbon black counteracts the effect of inhibiting

formation caused by the lignosulfonates.

Sulfonated naphthalene condensate dispersant is a more effective

expander than lignosulfonate and speeds up formation. This dispersant

improves dispersion of barium sulfate in the paste, reduces hydroset

time, produces a more breakage-resistant plate, reduces fine lead

particles and thereby improves handling and pasting characteristics. It

extends battery life by increasing end–of–charge voltage. Sulfonated

naphthalene requires about one-third to one-half the amount of

lignosulfonate and is stable to higher temperatures.[7]

Practical cells are usually not made with pure lead but have small

amounts of antimony, tin, calcium or selenium alloyed in the plate

material to add strength and simplify manufacture. The alloying element

has a great effect on the life of the batteries, with calcium-alloyed plates

preferred over antimony for longer life and less water consumption on

each charge/discharge cycle.

About 60% of the weight of an automotive-type lead–acid battery rated

around 60 Ah (8.7 kg of a 14.5 kg battery) is lead or internal parts made

of lead; the balance is electrolyte, separators, and the case.[6]

[edit]Separators

Separators between the positive and negative plates prevent short-

circuit through physical contact, mostly through dendrites (‘treeing’), but

also through shedding of the active material. Separators obstruct the

flow of ions between the plates and increase the internal resistance of

the cell. Wood, rubber, glass fiber mat, cellulose,

and PVC or polyethylene plastic have been used to make separators.

Wood was the original choice, but deteriorated in the acid electrolyte.

Rubber separators were stable in the battery acid.

An effective separator must possess a number of mechanical properties;

such as permeability, porosity, pore size distribution, specific surface

area, mechanical design and strength, electrical resistance, ionic

conductivity, and chemical compatibility with the electrolyte. In service,

the separator must have good resistance to acid and oxidation. The area

of the separator must be a little larger than the area of the plates to

prevent material shorting between the plates. The separators must

remain stable over the battery's operating temperature range.

[edit]Applications

Most of the world's lead–acid batteries are automobile starting, lighting

and ignition (SLI) batteries, with an estimated 320 million units shipped

in 1999.[6] In 1992 about 3 million tons of lead were used in the

manufacture of batteries.

Wet cell stand-by (stationary) batteries designed for deep discharge are

commonly used in large backup power supplies for telephone and

computer centers, grid energy storage, and off-grid household electric

power systems.[8] Lead–acid batteries are used in emergency lighting in

case of power failure.

Traction (propulsion) batteries are used for in golf carts and other battery

electric vehicles. Large lead–acid batteries are also used to power

the electric motors in diesel-electric (conventional)submarines and are

used on nuclear submarines as well. Valve-regulated lead acid

batteries cannot spill their electrolyte. They are used in back-up

power supplies for alarm and smaller computer systems (particularly in

uninterruptible power supplies) and for electric scooters,

electric wheelchairs, electrified bicycles, marine applications, battery

electric vehicles or micro hybrid vehicles, and motorcycles.

Lead–acid batteries were used to supply the filament (heater) voltage,

with 2 V common in early vacuum tube (valve) radio receivers.

[edit]Cycles

[edit]Starting batteriesMain article: Car battery

Lead acid batteries designed for starting automotive engines are not

designed for deep discharge. They have a large number of thin plates

designed for maximum surface area, and therefore maximum current

output, but which can easily be damaged by deep discharge. Repeated

deep discharges will result in capacity loss and ultimately in premature

failure, as the electrodes disintegrate due tomechanical stresses that

arise from cycling. Starting batteries kept on continuous float charge will

have corrosion in the electrodes and result in premature failure. Starting

batteries should be kept open circuit but charged regularly (at least once

every two weeks) to prevent sulfation.

Starting batteries are lighter weight than deep cycle batteries of the

same battery dimensions, because the cell plates do not extend all the

way to the bottom of the battery case. This allows loose disintegrated

lead to fall off the plates and collect under the cells, to prolong the

service life of the battery. If this loose debris rises high enough it can

touch the plates and lead to failure of a cell, resulting in loss of battery

voltage and capacity.

[edit]Deep cycle batteriesMain article: Deep cycle battery

Specially designed deep-cycle cells are much less susceptible to

degradation due to cycling, and are required for applications where the

batteries are regularly discharged, such as photovoltaicsystems, electric

vehicles (forklift, golf cart, electric cars and other) and uninterruptible

power supplies. These batteries have thicker plates that can deliver

less peak current, but can withstand frequent discharging.[9]

Some batteries are designed as a compromise between starter (high-

current) and deep cycle batteries. They are able to be discharged to a

greater degree than automotive batteries, but less so than deep cycle

batteries. They may be referred to as "Marine/Motorhome" batteries, or

"leisure batteries".

[edit]Fast and slow charge and discharge

Charge current needs to match the ability of the battery to absorb the energy. Using

too large of a charge current on a small battery can lead to boiling and venting of the

electrolyte. In this image a VRLA battery case has ballooned due to the high gas

pressure developed during overcharge.

The capacity of a lead–acid battery is not a fixed quantity but varies

according to how quickly it is discharged. An empirical relationship exists

between discharge rate and capacity, known as Peukert's law.

When a battery is charged or discharged, this initially affects only the

reacting chemicals, which are at the interface between the electrodes

and the electrolyte. With time, the charge stored in the chemicals at the

interface, often called "interface charge", spreads by diffusion of these

chemicals throughout the volume of the active material.

If a battery has been completely discharged (e.g. the car lights were left

on overnight) and next is given a fast charge for only a few minutes, then

during the short charging time it develops only a charge near the

interface. The battery voltage may rise to be close to the charger voltage

so that the charging current decreases significantly. After a few hours

this interface charge will spread to the volume of the electrode and

electrolyte, leading to an interface charge so low that it may be

insufficient to start the car.[10]

On the other hand, if the battery is given a slow charge, which takes

longer, then the battery will become more fully charged. During a slow

charge the interface charge has time to redistribute to the volume of the

electrodes and electrolyte, while being replenished by the charger. The

battery voltage remains below the charger voltage throughout this

process allowing charge to flow into the battery.

Similarly, if a battery is subject to a fast discharge (such as starting a

car, a current draw of more than 100 amps) for a few minutes, it will

appear to go dead, exhibiting reduced voltage and power. However, it

may have only lost its interface charge. If the discharge is halted for a

few minutes the battery may resume normal operation at the appropriate

voltage and power for its state of discharge. On the other hand, if a

battery is subject to a slow, deep discharge (such as leaving the car

lights on, a current draw of less than 7 amps) for hours, then any

observed reduction in battery performance is likely permanent.

[edit]Valve regulated

In a valve regulated lead acid (VRLA) battery the hydrogen and oxygen

produced in the cells largely recombine into water. Leakage is minimal,

although some electrolyte still escapes if the recombination cannot keep

up with gas evolution. Since VRLA batteries do not require (and make

impossible) regular checking of the electrolyte level, they have been

called maintenance free batteries. However, this is somewhat of a

misnomer. VRLA cells do require maintenance. As electrolyte is lost,

VRLA cells "dry-out" and lose capacity. This can be detected by taking

regular internal resistance,conductance or impedance measurements.

Regular testing reveals whether more involved testing and maintenance

is required. Recent maintenance procedures have been developed

allowing "rehydration", often restoring significant amounts of lost

capacity.

VRLA types became popular on motorcycles around 1983,[11] because

the acid electrolyte is absorbed into the separator, so it cannot spill.[12] The separator also helps them better withstand vibration. They are

also popular in stationary applications such as telecommunications sites,

due to their small footprint and installation flexibility.[13]

The electrical characteristics of VRLA batteries differ somewhat from

wet-cell lead–acid batteries, requiring caution in charging and

discharging.

[edit]Sulfation

Lead–acid batteries lose the ability to accept a charge when discharged

for too long due to sulfation, the crystallization of lead sulfate. They

generate electricity through a double sulfate chemical reaction. Lead

and Lead(IV) Oxide, which are the active materials on the battery's

plates, react with sulfuric acid in the electrolyte to form lead sulfate. The

lead sulfate first forms in a finely divided,amorphous state, and easily

reverts to lead, lead oxide and sulfuric acid when the battery recharges.

As batteries cycle through numerous discharge and charges, the lead

sulfate slowly converts to a stable crystalline form that no longer

dissolves on recharging. Thus, not all the lead is returned to the battery

plates, and the amount of usable active material necessary for electricity

generation declines over time.

Sulfation occurs in all lead–acid batteries during normal operation. It

clogs the grids, impedes recharging and ultimately expands, cracking the

plates and destroying the battery. In addition, the sulfate portion (of the

lead sulfate) is not returned to the electrolyte as sulfuric acid. The large

crystals physically block the electrolyte from entering the pores of the

plates. Sulfation can be avoided if the battery is fully recharged

immediately after a discharge cycle.[14]

Sulfation also affects the charging cycle, resulting in longer charging

times, less efficient and incomplete charging, and higher battery

temperatures.

The process can often be at least partially prevented and/or reversed by

a desulfation technique called pulse conditioning, in which short but

powerful current surges are repeatedly sent through the damaged

battery. Over time, this procedure tends to break down and dissolve the

sulfate crystals, restoring some capacity.[15]

Higher temperature speeds both desulfation and sulfation, although too

much heat damages the battery by accelerating corrosion.

[edit]Stratification

A typical lead–acid battery contains a mixture with varying

concentrations of water and acid. There is a slight difference in density

between water and acid, and if the battery is allowed to sit idle for long

periods of time, the mixture can separate into distinct layers with the

water rising to the top and the acid sinking to the bottom. This results in

a difference of acid concentration across the surface of the plates, and

can lead to greater corrosion of the bottom half of the plates.[6]

Frequent charging and discharging tends to stir up the mixture, since

the electrolysis of water during charging forms hydrogen and oxygen

bubbles that rise and displace the liquid as the bubbles move upward.

Batteries in moving vehicles are also subject to sloshing and splashing in

the cells, as the vehicle accelerates, brakes, and turns.

[edit]Risk of explosion

Car battery after explosion

Excessive charging electrolyzes some of the water emitting hydrogen

and oxygen. This process is known as "gassing". Wet cells have open

vents to release any gas produced, and VRLA batteries rely on valves

fitted to each cell. Wet cells come with catalytic caps to recombine any

emitted hydrogen. A VRLA cell normally recombines

any hydrogen and oxygen produced inside the cell, but malfunction or

overheating may cause gas to build up. If this happens (e.g., by

overcharging) the valve vents the gas and normalizes the pressure,

producing a characteristic acid smell. Valves can sometimes fail

however, if dirt and debris accumulate, allowing pressure to build up.

If the accumulated hydrogen and oxygen within either a VRLA or wet cell

is ignited, an explosion results. The force can burst the plastic casing or

blow the top off the battery, spraying acid and casing shrapnel. An

explosion in one cell may ignite the combustible gas mixture in

remaining cells.

The cell walls of VRLA batteries typically swell when the internal

pressure rises. The deformation varies from cell to cell, and is greater at

the ends where the walls are unsupported by other cells. Such over-

pressurized batteries should be carefully isolated and discarded.

Personnel working near batteries at risk for explosion should protect

their eyes and exposed skin from burns due to spraying acid and fire by

wearing a face shield, overalls, and gloves. Using goggles instead of

a face shield sacrifices safety by leaving one's face exposed to acid and

heat from a potential explosion.

[edit]Environment

[edit]Environmental concerns

According to a 2003 report entitled, "Getting the Lead Out,"

by Environmental Defense and the Ecology Center of Ann Arbor, Mich.,

the batteries of vehicles on the road contained an estimated 2,600,000

metric tons (2,600,000 long tons; 2,900,000 short tons) of lead. Some

lead compounds are extremely toxic. Long-term exposure to even tiny

amounts of these compounds can cause brain and kidney damage,

hearing impairment, and learning problems in children.[16] The auto

industry uses over 1,000,000 metric tons (980,000 long tons; 1,100,000

short tons) every year, with 90% going to conventional lead-acid vehicle

batteries. While lead recycling is a well-established industry, more than

40,000 metric tons (39,000 long tons; 44,000 short tons) ends up in

landfills every year. According to the federal Toxic Release Inventory,

another 70,000 metric tons (69,000 long tons; 77,000 short tons) are

released in the lead mining and manufacturing process.[17]

Attempts are being made to develop alternatives (particularly for

automotive use) because of concerns about the environmental

consequences of improper disposal and of lead smelting operations,

among other reasons. Alternatives are unlikely to displace them for

applications such as engine starting or backup power systems, since the

batteries are low-cost although heavy.

[edit]RecyclingSee also: Automotive battery recycling

Lead–acid battery recycling is one of the most successful recycling

programs in the world. In the United States 97% of all battery lead was

recycled between 1997 and 2001.[18] An effective pollution control system

is a necessity to prevent lead emission. Continuous improvement in

battery recycling plants and furnace designs is required to keep pace

with emission standards for lead smelters.

[edit]Additives

Since the 1950s chemical additives have been used to reduce lead

sulfate build up on plates and improve battery condition when added to

the electrolyte of a vented lead–acid battery. Such treatments are rarely,

if ever, effective.[19]

Two compounds used for such purposes are Epsom salts and EDTA.

Epsom salts reduces the internal resistance in a weak or damaged

battery and may allow a small amount of extended life. EDTA can be

used to dissolve the sulfate deposits of heavily discharged plates.

However, the dissolved material is then no longer available to participate

in the normal charge/discharge cycle, so a battery temporarily revived

with EDTA will have a reduced life expectancy. Residual EDTA in the

lead–acid cell forms organic acids which will accelerate corrosion of the

lead plates and internal connectors.

The active materials change physical form during charge/discharge,

resulting in growth and distortion of the electrodes, and shedding of

electrode into the electrolyte. Once the active material has fallen out of

the plates, it cannot be restored into position by any chemical treatment.

Similarly, internal physical problems such as cracked plates, corroded

connectors, or damaged separators cannot be restored chemically.

[edit]Corrosion problems

Corrosion of the external metal parts of the lead–acid battery results

from a chemical reaction of the battery terminals, lugs and connectors.

Corrosion on the positive terminal is caused by electrolysis, due a

mismatch of metal alloys used in the manufacture of the battery terminal

and cable connector. White corrosion is usually lead or zinc

sulfate crystals. Aluminum connectors corrode to aluminum sulfate.

Copper connectors produce blue and white corrosion crystals. Corrosion

of a battery's terminals can be reduced by coating the terminals with

petroleum jelly[citation needed] or a commercially available product made for

the purpose.

If the battery is over-filled with water and electrolyte, thermal expansion

can force some of the liquid out of the battery vents onto the top of the

battery. This solution can then react with the lead and other metals in the

battery connector and cause corrosion.

The electrolyte can weep from the plastic-to-lead seal where the battery

terminals penetrate the plastic case.

Acid fumes that vaporize through the vent caps, often caused by

overcharging, and insufficient battery box ventilation can allow the

sulfuric acid fumes to build up and react with the exposed metals.

Electric Generator

In electricity generation, an electric generator is a device that converts mechanical

energy to electrical energy. A generator forces electric charge (usually carried

by electrons) to flow through an external electrical circuit. It is analogous to a water

pump, which causes water to flow (but does not create water). The source of

mechanical energy may be a reciprocating or turbine steam engine, water falling

through a turbine or waterwheel, an internal combustion engine, a wind turbine, a

handcrank, compressed air or any other source of mechanical energy.

Early 20th century alternator made inBudapest, Hungary, in the power generating hall of

a hydroelectric station

Early Ganz Generator in Zwevegem,West Flanders, Belgium

The reverse conversion of electrical energy into mechanical energy is done by

an electric motor, and motors and generators have many similarities. In fact many

motors can be mechanically driven to generate electricity, and very frequently make

acceptable generators.

DynamoMain article: Dynamo

Dynamos are no longer used for power generation due to the size and complexity of the commutator

needed for high power applications. This large belt-driven high-current dynamo produced 310

amperes at 7 volts, or 2,170 watts, when spinning at 1400 RPM.

Dynamo Electric Machine [End View, Partly Section] (U.S. Patent 284,110)

The dynamo was the first electrical generator capable of delivering power for

industry. The dynamo uses electromagnetic principles to convert mechanical rotation

into pulsed DC through the use of acommutator. The first dynamo was built

by Hippolyte Pixii in 1832.

Through a series of accidental discoveries, the dynamo became the source of many

later inventions, including the DC electric motor, the AC alternator, the

AC synchronous motor, and the rotary converter.

A dynamo machine consists of a stationary structure, which provides a constant

magnetic field, and a set of rotating windings which turn within that field. On small

machines the constant magnetic field may be provided by one or more permanent

magnets; larger machines have the constant magnetic field provided by one or more

electromagnets, which are usually called field coils.

Large power generation dynamos are now rarely seen due to the now nearly universal

use of alternating current for power distribution and solid state electronic AC to DC

power conversion. But before the principles of AC were discovered, very large direct-

current dynamos were the only means of power generation and distribution. Now

power generation dynamos are mostly a curiosity.

[edit]Alternator

Without a commutator, a dynamo becomes an alternator, which is a synchronous

singly fed generator. When used to feed an electric power grid, an alternator must

always operate at a constant speed that is precisely synchronized to the electrical

frequency of the power grid. A DC generator can operate at any speed within

mechanical limits, but always outputs direct current.

Typical alternators use a rotating field winding excited with direct current, and a

stationary (stator) winding that produces alternating current. Since the rotor field only

requires a tiny fraction of the power generated by the machine, the brushes for the

field contact can be relatively small. In the case of a brushless exciter, no brushes are

used at all and the rotor shaft carries rectifiers to excite the main field winding.

[edit]Other rotating electromagnetic generators

Other types of generators, such as the asynchronous or induction singly fed

generator, the doubly fed generator, or the brushless wound-rotor doubly fed

generator, do not incorporate permanent magnets or field windings (i.e.,

electromagnets) that establish a constant magnetic field, and as a result, are seeing

success in variable speed constant frequency applications, such as wind turbines or

other renewable energy technologies.

The full output performance of any generator can be optimized with electronic control

but only the doubly fed generators or the brushless wound-rotor doubly fed

generator incorporate electronic control with power ratings that are substantially less

than the power output of the generator under control, a feature which, by itself, offers

cost, reliability and efficiency benefits.

[edit]MHD generatorMain article: MHD generator

A magnetohydrodynamic generator directly extracts electric power from moving hot

gases through a magnetic field, without the use of rotating electromagnetic machinery.

MHD generators were originally developed because the output of a plasma MHD

generator is a flame, well able to heat the boilers of a steam power plant. The first

practical design was the AVCO Mk. 25, developed in 1965. The U.S. government

funded substantial development, culminating in a 25 MW demonstration plant in 1987.

In the Soviet Union from 1972 until the late 1980s, the MHD plant U 25 was in regular

commercial operation on the Moscow power system with a rating of 25 MW, the

largest MHD plant rating in the world at that time.[2] MHD generators operated as

a topping cycle are currently (2007) less efficient than combined-cycle gas turbines.

[edit]Terminology

The two main parts of a generator or motor can be described in either mechanical or

electrical terms.

Mechanical:

Rotor : The rotating part of an electrical machine

Stator : The stationary part of an electrical machine

Electrical:

Armature : The power-producing component of an electrical machine. In a

generator, alternator, or dynamo the armature windings generate the electric

current. The armature can be on either the rotor or the stator.

Field : The magnetic field component of an electrical machine. The magnetic

field of the dynamo or alternator can be provided by either electromagnets or

permanent magnets mounted on either the rotor or the stator.

Because power transferred into the field circuit is much less than in the armature

circuit, AC generators nearly always have the field winding on the rotor and the stator

as the armature winding. Only a small amount of field current must be transferred to

the moving rotor, using slip rings. Direct current machines (dynamos) require

a commutator on the rotating shaft to convert the alternating currentproduced by the

armature to direct current, so the armature winding is on the rotor of the machine.

[edit]Excitation

A small early 1900s 75 KVA direct-driven power station AC alternator, with a separate belt-driven

exciter generator.

Main article: Excitation (magnetic)

An electric generator or electric motor that uses field coils rather than permanent

magnets requires a current to be present in the field coils for the device to be able to

work. If the field coils are not powered, the rotor in a generator can spin without

producing any usable electrical energy, while the rotor of a motor may not spin at all.

Smaller generators are sometimes self-excited, which means the field coils are

powered by the current produced by the generator itself. The field coils are connected

in series or parallel with the armature winding. When the generator first starts to turn,

the small amount of remanent magnetism present in the iron core provides a magnetic

field to get it started, generating a small current in the armature. This flows through

the field coils, creating a larger magnetic field which generates a larger armature

current. This "bootstrap" process continues until the magnetic field in the core levels

off due to saturation and the generator reaches a steady state power output.

Very large power station generators often utilize a separate smaller generator to

excite the field coils of the larger. In the event of a severe widespread power

outage where islanding of power stations has occurred, the stations may need to

perform ablack start to excite the fields of their largest generators, in order to restore

customer power service.[3]

[edit]Equivalent circuit

Equivalent circuit of generator and load.

G = generator

VG=generator open-circuit voltage

RG=generator internal resistance

VL=generator on-load voltage

RL=load resistance

The equivalent circuit of a generator and load is shown in the diagram to the right. The

generator's VG and RG parameters can be determined by measuring the winding

resistance (corrected to operating temperature), and measuring the open-circuit and

loaded voltage for a defined current load.

[edit]Vehicle-mounted generators

Early motor vehicles until about the 1960s tended to use DC generators with

electromechanical regulators. These have now been replaced by alternators with built-

in rectifier circuits, which are less costly and lighter for equivalent output. Moreover,

the power output of a DC generator is proportional to rotational speed, whereas the

power output of an alternator is independent of rotational speed. As a result, the

charging output of an alternator at engine idle speed can be much greater than that of

a DC generator. Automotive alternators power the electrical systems on the vehicle

and recharge the battery after starting. Rated output will typically be in the range 50-

100 A at 12 V, depending on the designed electrical load within the vehicle. Some

cars now have electrically poweredsteering assistance and air conditioning, which

places a high load on the electrical system. Large commercial vehicles are more likely

to use 24 V to give sufficient power at the starter motor to turn over a large diesel

engine. Vehicle alternators do not use permanent magnets and are typically only 50-

60% efficient over a wide speed range.[4] Motorcycle alternators often use permanent

magnet stators made with rare earth magnets, since they can be made smaller and

lighter than other types. See also hybrid vehicle.

Some of the smallest generators commonly found power bicycle lights. These tend to

be 0.5 ampere, permanent-magnet alternators supplying 3-6 W at 6 V or 12 V. Being

powered by the rider, efficiency is at a premium, so these may incorporate rare-earth

magnets and are designed and manufactured with great precision. Nevertheless, the

maximum efficiency is only around 80% for the best of these generators—60% is

more typical—due in part to the rolling friction at the tyre–generator interface from

poor alignment, the small size of the generator, bearing losses and cheap design. The

use of permanent magnets means that efficiency falls even further at high speeds

because the magnetic field strength cannot be controlled in any way. Hub generators

remedy many of these flaws since they are internal to the bicycle hub and do not

require an interface between the generator and tyre. Until recently, these generators

have been expensive and hard to find. Major bicycle component manufacturers like

Shimano and SRAM have only just entered this market. However, significant gains

can be expected in future as cycling becomes more mainstream transportation and

LED technology allows brighter lighting at the reduced current these generators are

capable of providing.

Sailing yachts may use a water or wind powered generator to trickle-charge the

batteries. A small propeller, wind turbine or impeller is connected to a low-power

alternator and rectifier to supply currents of up to 12 A at typical cruising speeds.

[edit]Engine-generator

Main article: Engine-generator

An engine-generator is the combination of an electrical generator and

an engine (prime mover) mounted together to form a single piece of self-contained

equipment. The engines used are usually piston engines, but gas turbines can also be

used. Many different versions are available - ranging from very small

portable petrol powered sets to large turbine installations.

[edit]Human powered electrical generators

Main article: Self-powered equipment

Protesters at Occupy Wall Street using bicycles connected to a motor and one-way diode to charge

batteries for their electronics[5]

A generator can also be driven by human muscle power (for instance, in field radio

station equipment).

Human powered direct current generators are commercially available, and have been

the project of some DIY enthusiasts. Typically operated by means of pedal power, a

converted bicycle trainer, or a foot pump, such generators can be practically used to

charge batteries, and in some cases are designed with an integral inverter. The

average adult could generate about 125-200 watts on a pedal powered generator, but

at a power of 200 W, a typical healthy human will reach complete exhaustion and fail

to produce any more power after approximately 1.3 hours.[6] Portable radio receivers

with a crank are made to reduce battery purchase requirements, see clockwork radio.

During the mid 20th century, pedal powered radios were used throughout the

Australian outback, to provide schooling,(school of the air) medical and other needs in

remote stations and towns.

[edit]Linear electric generator

In the simplest form of linear electric generator, a sliding magnet moves back and

forth through a solenoid - a spool of copper wire. An alternating current is induced in

the loops of wire by Faraday's law of induction each time the magnet slides through.

This type of generator is used in the Faraday flashlight. Larger linear electricity

generators are used in wave power schemes.

[edit]Tachogenerator

Tachogenerators are frequently used to power tachometers to measure the speeds of

electric motors, engines, and the equipment they power. Generators generate voltage

roughly proportional to shaft speed. With precise construction and design, generators

can be built to produce very precise voltages for certain ranges of shaft speeds

Starter motorFrom Wikipedia, the free encyclopedia

This article is about engine starters. For other kinds of starters, see Starter (disambiguation).

An automobile starter motor

A starter motor (also starting motor or starter) is an electric motor for rotating an internal-combustion engine so as

to initiate the engine's operation under its own power.

Electric starter

1. Main Housing (yoke)

2. Overrunning clutch , and Pinion gear assembly

3. Armature

4. Field coils  with Brushes attached

5. Brush-carrier

6. Solenoid

The modern starter motor is either a permanent-magnet or a series-parallel

wound direct current electric motor with a starter solenoid (similar to a relay) mounted

on it. When current from the starting battery is applied to the solenoid, usually through

a key-operated switch, the solenoid engages a lever that pushes out the

drive pinion on the starter driveshaft and meshes the pinion with the starter ring

gear on the flywheel of the engine.

The solenoid also closes high-current contacts for the starter motor, which begins to

turn. Once the engine starts, the key-operated switch is opened, a spring in the

solenoid assembly pulls the pinion gear away from the ring gear, and the starter motor

stops. The starter's pinion is clutched to its driveshaft through an overrunning sprag

clutch which permits the pinion to transmit drive in only one direction. In this manner,

drive is transmitted through the pinion to the flywheel ring gear, but if the pinion

remains engaged (as for example because the operator fails to release the key as

soon as the engine starts, or if there is a short and the solenoid remains engaged),

the pinion will spin independently of its driveshaft. This prevents the engine driving the

starter, for such backdrive would cause the starter to spin so fast as to fly apart.

However, this sprag clutch arrangement would preclude the use of the starter as a

generator if employed in hybrid scheme mentioned above, unless modifications were

made. Also, a standard starter motor is only designed for intermittent use which would

preclude its use as a generator; the electrical components are designed only to

operate for typically under 30 seconds before overheating (by too-slow dissipation of

heat from ohmic losses), to save weight and cost. This is the same reason why most

automobile owner's manuals instruct the operator to pause for at least ten seconds

after each ten or fifteen seconds of cranking the engine, when trying to start an engine

that does not start immediately.

This overrunning-clutch pinion arrangement was phased into use beginning in the

early 1960s; before that time, a Bendix drive was used. The Bendix system places the starter

drive pinion on a helically cut driveshaft. When the starter motor begins turning, the inertia of the

drive pinion assembly causes it to ride forward on the helix and thus engage with the ring gear. When

the engine starts, backdrive from the ring gear causes the drive pinion to exceed the rotative speed of

the starter, at which point the drive pinion is forced back down the helical shaft and thus out of mesh

with the ring gear.

Hear a Folo-Thru starter

A starter motor with Bendix Folo-Thru drive cranks a Chrysler Slant-6 engine. The Folo-Thru drive pinion stays engaged through a cylinder firing but not causing the engine to start

Problems listening to this file? See media help.

An intermediate development between the Bendix drive developed in the 1930s and

the overrunning-clutch designs introduced in the 1960s was the Bendix Folo-Thru

drive. The standard Bendix drive would disengage from the ring gear as soon as the

engine fired, even if it did not continue to run. The Folo-Thru drive contains a latching

mechanism and a set of flyweights in the body of the drive unit. When the starter

motor begins turning and the drive unit is forced forward on the helical shaft by inertia,

it is latched into the engaged position. Only once the drive unit is spun at a speed

higher than that attained by the starter motor itself (i.e., it is backdriven by the running

engine) will the flyweights pull radially outward, releasing the latch and permitting the

overdriven drive unit to be spun out of engagement. In this manner, unwanted starter

disengagement is avoided before a successful engine start.

[edit]Gear reduction

Hear a gear-reduction starter

A Chrysler gear-reduction starter cranks a V8 engine

Problems listening to this file? See media help.

Chrysler Corporation contributed materially to the modern development of the starter

motor. In 1962, Chrysler introduced a starter incorporating ageartrain between the

motor and the driveshaft. Rolls Royce had introduced a conceptually similar starter in

1946,[citation needed] but Chrysler's was the first volume-production unit. The motor shaft

has integrally cut gear teeth forming a pinion which meshes with a larger adjacent

driven gear to provide a gear reduction ratio of 3.75:1. This permits the use of a

higher-speed, lower-current, lighter and more compact motor assembly while

increasing cranking torque.[3] Variants of this starter design were used on most rear-

and four-wheel-drive vehicles produced by Chrysler Corporation from 1962 through

1987. It makes a unique, distinct sound when cranking the engine, which led to it

being nicknamed the "Highland Park Hummingbird"—a reference to Chrysler's

headquarters in Highland Park, Michigan.[4]

The Chrysler gear-reduction starter formed the conceptual basis for the gear-

reduction starters that now predominate in vehicles on the road. Many Japanese

automakers phased in gear reduction starters in the 1970s and 1980s.[citation needed] Light

aircraft engines also made extensive use of this kind of starter, because its light

weight offered an advantage.

Those starters not employing offset geartrains like the Chrysler unit generally employ

planetary epicyclic geartrains instead. Direct-drive starters are almost entirely

obsolete owing to their larger size, heavier weight and higher current requirements.[citation needed]

[edit]Movable pole shoe

Ford also issued a nonstandard starter, a direct-drive "movable pole shoe" design that

provided cost reduction rather than electrical or mechanical benefits. This type of

starter eliminated the solenoid, replacing it with a movable pole shoe and a separate

starter relay. This starter operates as follows: The driver turns the key, activating the

starter switch. A small electric current flows through the switch-type starter solenoid,

closing the contacts and sending large battery current to the starter motor. One of the

pole shoes, hinged at the front, linked to the starter drive, and spring-loaded away

from its normal operating position, is swung into position by the magnetic field created

by electricity flowing through its field coil. This moves the starter drive forward to

engage the flywheel ring gear, and simultaneously closes a pair of contacts supplying

current to the rest of the starter motor winding. Once the engine starts and the driver

releases the starter switch, a spring retracts the pole shoe, which pulls the starter

drive out of engagement with the ring gear.

This starter was used on Ford vehicles from 1973 through 1990, when a gear-

reduction unit conceptually similar to the Chrysler unit replaced it.

[edit]Pneumatic starter

Main article: Air start system

Some gas turbine engines and Diesel engines, particularly on trucks, use

a pneumatic self-starter. The system consists of a geared turbine, an air

compressor and a pressure tank. Compressed air released from the tank is used to

spin the turbine, and through a set of reduction gears, engages the ring gear on the

flywheel, much like an electric starter. The engine, once running, powers the

compressor to recharge the tank.

Aircraft with large gas turbine engines are typically started using a large volume of

low-pressure compressed air, supplied from a very small engine referred to as

an auxiliary power unit, located elsewhere in the aircraft. After starting the main

engines, the APU often continues to operate, supplying additional power to operate

aircraft equipment. Alternately, aircraft engines can be rapidly started using a mobile

ground-based pneumatic starting engine, referred to as a start cart or air start cart.

On larger diesel generators found in large shore installations and especially on ships,

a pneumatic starting gear is used. The air motor is normally powered by compressed

air at pressures of 10–30 bar. The air motor is made up of a center drum about the

size of a soup can with four or more slots cut into it to allow for the vanes to be placed

radially on the drum to form chambers around the drum. The drum is offset inside a

round casing so that the inlet air for starting is admitted at the area where the drum

and vanes form a small chamber compared to the others. The compressed air can

only expand by rotating the drum which allows the small chamber to become larger

and puts another one of the cambers in the air inlet. The air motor spins much too fast

to be used directly on the flywheel of the engine, instead a large gearing reduction

such as a planetary gear is used to lower the output speed. A Bendix gear is used to

engage the flywheel.

On large diesel generators and almost all diesel engines used as the prime mover of

ships will use compressed air acting directly on the cylinder head. This is not ideal for

smaller diesels as it provides too much cooling on starting. Also the cylinder head

needs to have enough space to support an extra valve for the air start system. The air

start system operates very similar to a distributor in a car. There is an air distributor

that is geared to the camshaft of the diesel engine, on the top of the air distributor is a

single lobe similar to what is found on a camshaft. Arranged radially around this lobe

are roller tip followers for every cylinder. When the lobe of the air distributor hits one of

the followers it will send an air signal that acts upon the back of the air start valve

located in the cylinder head causing it to open. The actual compressed air is provided

from a large reservoir that feeds into a header located along the engine. As soon as

the air start valve is opened the compressed air is admitted and the engine will begin

turning. It can be used on 2-cycle and 4-cycle engines and on reversing engines. On

large 2-stroke engines less than one revolution of the crankshaft is needed for

starting.

Since large trucks typically use air brakes, the system does double duty, supplying

compressed air to the brake system. Pneumatic starters have the advantages of

delivering high torque, mechanical simplicity and reliability. They eliminate the need

for oversized, heavy storage batteries in prime mover electrical systems.

[edit]Hydraulic starter

This section does not cite any references or sources. Please help improve

this section by adding citations to reliable sources. Unsourced material may

be challenged and removed. (December 2010)

Some diesel engines from 6 to 16 cylinders are started by means of a hydraulic motor.

Hydraulic starters and the associated systems provide a sparkless, reliable method of engine starting at

a wide temperature range. Typically hydraulic starters are found in applications such as remote

generators, lifeboat propulsion engines, offshore fire pumping engines, and hydraulic fracturing rigs.

The system used to support the hydraulic starter includes valves, pumps, filters, a reservoir, and piston

accumulators. The operator can manually recharge the hydraulic system; this cannot readily be done

with air or electric starting systems, so hydraulic starting systems are favored in applications wherein

emergency starting is a requirement.

Hydraulic Starter Hydraulic Starter

[edit]Other methods

Before the advent of the starter motor, engines were started by various methods

including wind-up springs, gun powder cylinders, and human-powered techniques

such as a removable crank handle which engaged the front of the crankshaft, pulling

on an airplane propeller, or pulling a cord that was wound around an open-face pulley.

The behavior of an engine during starting is not always predictable. The engine can

kick back, causing sudden reverse rotation. Many manual starters included a one-

directional slip or release provision so that once engine rotation began, the starter

would disengage from the engine. In the event of a kickback, the reverse rotation of

the engine could suddenly engage the starter, causing the crank to unexpectedly and

violently jerk, possibly injuring the operator. For cord-wound starters, a kickback could

pull the operator towards the engine or machine, or swing the starter cord and handle

at high speed around the starter pulley.

Self starting

Some modern gasoline engines with twelve or more cylinders always have at least

one piston at the beginning of its power stroke and are able to start by injecting fuel

into that cylinder and igniting it.

MagnetoFrom Wikipedia, the free encyclopedia

For other uses, see Magneto (disambiguation).

Demonstration hand-cranked magneto

A magneto is an electrical generator that uses permanent magnets to produce alternating current.

Hand-cranked magneto generators were used to provide ringing current in early telephone systems.

Magnetos adapted to produce pulses of high voltage are used in the ignition systems of some gasoline-

powered internal combustion engines to provide power to the spark plugs.[1] The magneto is now confined mainly to

engines where there is no available electrical supply, for example in lawnmowers and chainsaws. It is also universally

used in aviation piston engines even though an electrical supply is usually available. This is because a magneto

ignition system is more reliable than a battery-coil system.

Magnetos were rarely used for power generation, although they were for a few specialised uses.

Power generation

For more details on this topic, see Magneto (generator).

Magnetos have advantages of simplicity and reliability, but are inefficient owing to the

weak magnetic flux available from their permanent magnets. This restricted their use

for high-power applications. Power generation magnetos were limited to narrow fields,

such as powering arc lamps or lighthouses, where their particular features of output

stability or simple reliability were most valued.

[edit]Bicycles

One popular and common use of magnetos of today is for powering lights on bicycles.

Most commonly a small magneto, termed a bottle dynamo, rubs against the tyre of the

bicycle and generates power as the wheel turns.

More expensive and less common but more efficient is the hub dynamo.

Although commonly referred to as dynamos, both devices are in fact magnetos,

producing alternating current as opposed to the direct current produced by a

true dynamo.

[edit]Medical use

The magneto also had a medical use for treatment of mental illness in the beginnings

of electromedicine. In 1850, Duchenne, a French doctor, developed and

manufactured a magneto with a variable outer voltage and frequency, through varying

revolutions by hand or varying the inductance of the two coils, putting out or putting in

both ferromagnetic cores.

[edit]Ignition magnetos

Main article: Ignition magneto

It has been suggested that Ignition magneto be merged into this article or

section. (Discuss) Proposed since July 2011.

Magnetos adapted to produce impulses of high voltage for spark plugs are used in the

ignition systems of spark-ignition piston engines. Magnetos are used in piston aircraft

engines for their reliability and simplicity. Motor sport vehicles such

as motorcycles and snowmobiles use magnetos because they are lighter in weight

than an ignition system relying on a battery. Small internal combustion engines used

for lawn mowers, chain saws, portable pumps and similar applications use magnetos

for economy and weight reduction. Magnetos are not used in highway motor vehicles

which have a cranking battery and which may require more control over ignition timing

than is possible with a magneto system.

[edit]Telephone

1896 Telephone, hand crank for magneto on right (Sweden)

For more details on this topic, see Telephone magneto.

Many early manual telephones had a hand cranked "magneto" generator to produce a

(relatively) high voltage alternating signal to ring the bells of other telephones on the

same (party) line and to alert the operator. These were usually on long rural lines

served by small manual exchanges, which were not "common battery". The telephone

instrument was "local battery", containing two large "No. 6" zinc-carbon dry cells.

Regulator (automatic control)From Wikipedia, the free encyclopedia

In automatic control, a regulator is a device which has the function of maintaining a designated characteristic. It

performs the activity of managing or maintaining a range of values in a machine. The measurable property of a device

is managed closely by specified conditions or an advance set value; or it can be a variable according to a

predetermined arrangement scheme. It can be used generally to connote any set of various controls or devices for

regulating or controlling items or objects.

Examples are a voltage regulator (which can be a transformer whose voltage ratio of transformation can be adjusted,

or an electronic circuit that produces a defined voltage), a pressure regulator, such as a diving regulator, which

maintains its output at a fixed pressure lower than its input, and a fuel regulator (which controls the supply of fuel).

Regulators can be designed to control anything from gases or fluids, to light or electricity. Speed can be regulated by

electronic, mechanical, or electro-mechanical means. Such instances include;

Electronic regulators as used in modern railway sets where the voltage is raised or lowered to control the

speed of the engine

Mechanical systems such as valves as used in fluid control systems. Purely mechanical pre-automotive

systems included such designs as the Watt centrifugal governor whereas modern systems may have electronic

fluid speed sensing components directing solenoids to set the valve to the desired rate.

Complex electro-mechanical speed control systems used to maintain speeds in modern cars (cruise control) -

often including hydraulic components,

An aircraft engine's constant speed unit changes the propellor pitch to maintain engine speed.

[edit]See also