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INTRODUCTION

In trying to keep up with emissions and fuel efficiency laws, the fuel system used in moderncars has changed a lot over the years. The 1990 Subaru Justy was the last car sold in the

United States to have a carburetor; the following model year, the Justy had fuel injection.

But fuel injection has been around since the 1950s, and electronic fuel injection was used

widely on European cars starting around 1980. Now, all cars sold in the United States have

fuel injection systems.

Air pollution has been the main reason due to which all the developed countries have

switched over to Electronic Fuel Injection system. Not only air pollution but keeping in

mind rise in fuel prices day by day, fuel economy is also one of the reasons leading to the

transformation from carburetors to injection system. Electronic control over the injection

system has made it much easier to control the engine functioning. Earlier cold starting was

achieved by heating the intake manifold with the help of a glow plug. But now EFI has

introduced a separate injector called cold start injector which makes the charge rich by

injecting an extra amount of fuel in the intake manifold.

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HISTORY OF FUEL INJECTION

(1) Fuel Injection: Diesel engines from the very beginning have been using fuel

injection system. But the year 1903 is a memorable year in the history of IC engine

development. It was in this year that the Wright brothers made the maiden SI engine

powdered flight which had a gear pump that injected fuel into the intake port. Thus

fuel injection in case of SI engine is not a recent development.

(2) Air injection : Developed in around 1895. Fuel oil was metered and delivered by a

pump to the atomizer, which was in communication with a high pressure air storagetank supplied by an air compressor, and injection occurred when the injector valve

was opened by a cam actuated mechanism. High pressure air then flowed into the

engine cylinder carrying along with it the metered fuel as a finely atomized spray.

The use of bulky compressors led to its obsolete use.

(3) Solid injection:(a) Mechanical injectors: The first satisfactory airless injection system was

James McKechnie of Vickers in 1910. Here the fuel was injected without

the use of any high pressure air from the compressor. Oil was delivered

by a metering pump to a spring loaded plunger, which was raised by a

cam. Tripping of the cam allowed the fuel to be injected into the engine

cylinder as the spring returned the plunger t o its bottom position.

(b) Automatic or differential valve injectors: The inwardly opening

differential valve type nozzle , which is most commonly used today was

first used by Thornycroft of England in 1908. It consists of a spring

loaded needle valve which was operated hydraulically by the pressure of

the fuel. Differential areas were used on the valve stem to augment the

fuel pressure to lift the needle valve.

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(4) Electro-magnetically operated valves: The idea of lifting nozzles by solenoids was

first introduced by an American named Thomas T Gaff in 1913 but was finally

experimented and brought up by another American in 1933. This was the beginning

of the Electronic Fuel injection System. It was commercially used by AMC in its

model Rambler Rebel in 1956 . But due to cold starting defects it couldnt be

successful.

(5) Gasoline injection: The first ever IC engine to use gasoline injection was Chevrolet

Corvette of the General Motors in 1957. It was a mechanical fuel injection system.

(6) ECU: In 1980, Motorola introduced the first electronic engine

control unit. Its integrated control of engine functions (such as fuel

injection and spark timing) is now the standard approach for fuel

injection systems. [1]

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WHY EFI ?

The fuel injection from the very beginning in 1903 has undergone vast transformations.

Electronic Fuel Injection system is going to be the sole injection system in the near future.

All the vehicles running in developed countries have already been restricted to fuel injection

systems be it for diesel or gasoline. E.g. USA, Canada, Germany etc. [1]

For developing countries carburetors are still prevailing but they too are undergoing

this transformation to EFI.

EFI is used because of :

(1) Pollution control:

In the present era the environmental air pollution is mainly caused due to vehicular

emissions. Various gases emitted are carbon dioxide, carbon dioxide, nitrogen dioxide, etc.

In EFI systems various sensors are employed like the exhaust gas oxygen sensors. It senses

the amount of oxygen in the exhaust emissions and the ECU adjusts the thereafter fuel

requirements. If more oxygen is detected then rich fuel is injected and if less oxygen is

detected then rich fuel is injected.

(2) Fuel economy:

Rise in fuel price is a matter of concern today. Therefore we either have to find an

alternative source to such fuels or utilize the present fuel in an economical and efficient

manner. The alternatives should be much cheaper and be abundantly available. EFI system

plays an important role in using the fuel economically. The ECU along with the feedback

available from various sensors meter the fuel in a very precise manner and fuel wastage is

negligible.

(3) Decreasing cost of electronic components:

The day to day decrease in the prices of electronic components is a good sign in this field.

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FUEL DELIVERY SYSTEM IN EFI

The fuel supply from the fuel tank to the injector valves for all electronic systems follows

the same basic layout. The delivery of fuel at the injector valves is also based on a similar

function for all systems. It basically consists of fuel tank, electrical fuel pump, fuel pressure

regulator, fuel injector, fuel return pipe and fuel filter.

(a) Fuel tank:

It is used for the storage purpose of the fuel. The fuel tank is the obvious place to start in

any full system explanation. Unlike the tanks on early carburetor cars, it is a sealed unit that

allows the natural gassing of the fuel to aid delivery to the pump by slightly pressursing the

system. It may be noted that when the filler cap is removed, that pressure is heard to escape

(b) Electrical fuel pump:

It draws fuel from tank and forces it into the regulator. Fuel injected engines often use

electric fuel pumps that are mounted inside the fuel tank (and some fuel injected engines

have two fuel pumps: one low pressure/high volume supply pump in the tank and one high

pressure/low volume pump on or near the engine.) . Placing the pump in the tank puts the

component least likely to handle fuel vapour well (the pump itself) farthest from the engine,

submerged in cool liquid. Another benefit to placing the pump inside the tank is that it is

less likely to start a fire. Though electrical components (such as a fuel pump) can spark and

ignite fuel vapors, liquid fuel will not explode and therefore submerging the pump in the

tank is one of the safest places to put it. In most cars, the fuel pump delivers a constant flow

of gasoline to the engine; fuel not used is returned to the tank. This further reduces the

chance of the fuel boiling, since it is never kept close to the hot engine for too long.

(c) Fuel pressure regulator:

It controls the amount of pressure that enters the injector and any extra fuel is returned to

the fuel tank. The fuel pressure regulator is fitted to maintain a precise pressure at the fuel

injector valve nozzles. On port fuel-injection systems, a fuel rail is used to hold the pressure

regulator and the fuel feed to the injector valves. The injector valves usually fit directly onto

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or into the fuel rail. The fuel rail holds sufficient fuel to dampen fuel pressure fluctuations

and keep the pressure applied at all injector nozzles at a similar level.

Fuel pressure regulators are sealed units with a spring-loaded diaphragm and valve

on the return outlet to the fuel tank. Fuel is pumped into the regulator, and when the pressure

is high enough it acts against the diaphragm and compression spring to open the valve.

Surplus pressure and fuel is allowed to return to the fuel tank. Once the pressure in the fuel

regulator is reduced, the valve closes and the pressure builds up again. Throttle-body

injection systems operate in the region of 1 bar, and port fuel injection systems in the region

of 2.5 bars.

(d) Electrical fuel injectors:

The injector valves spray finely atomized fuel into the throttle body or inlet ports,

depending on the system. The electromagnetic injection valves are actuated by signals from

the ECU. These are an electromagnetic solenoid, a spring-loaded plunger, a jet needle and

the injector-valve nozzle. The electrical supply to the solenoid is made from the system relay

or ECU. Grounding the other connection energizes the solenoid. This lifts the plunger and

jet needle so that fuel is injected for the duration that the electrical current remains live. As

soon as the electrical supply is switched off in the ECU, a compression spring in the injector

valve acts on the solenoid plunger to close the nozzle.

Figure 1: Solenoid fuel injectors [2]

(e) Fuel return pipe:

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The return pipe run from the fuel pressure regulator to the fuel tank. . Surplus pressure

and fuel in the fuel pressure regulator is allowed to return to the fuel tank.

(f) Fuel filter:

The fuel filter is an in-line paper element type that is replaced at scheduled service intervals.

The filter uses micro-porous paper that is directional for filtration. Filters are marked for fuel

flow with an arrow on the casing. Correct fitting is essential. The fuel filter is the fuelsystem's primary line of defense against dirt, debris and small particles of rust that flake off

the inside of the fuel tank. [2]

(g) Accumulator:

It is used to maintain the fuel pressure. When the engine is in off positon it maintains the

fuel pressure so that it can be restarted.

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AIR INDUCTION SYSTEM

The air-supply components consist of ducting and silencing components between the air

intake and the inlet manifolds. This also includes an air filter, a throttle body, throttle plate

assembly and idle control components. The air-supply components must provide sufficient

clean air for all operating conditions.

(a) Air filter:

Air filters on most modern gasoline-engined vehicles consist of a plastic casing with a paper

filter element. Airflow into the filter is upwards so that dust and dirt particles drop into the

dust chamber, or is rotary so that dust and dirt is thrown out before the air enters the engine.

Crankcase ventilation and the air supply or pulse air exhaust emission systems are also

connected to the filter assembly.

(b) Throttle body:

A throttle is the mechanism by which the flow of a fluid is managed by constriction orobstruction. An engine's power can be increased or decreased by the restriction of inlet

gases. The throttle is a conventional circular plate in an air tube. For fast idle and warm-up,

an auxiliary air valve is fitted to bypass the throttle plate, or an electromechanical link is

made to the throttle plate spindle

When you step on the gas pedal, the throttle valve opens up more, letting in more air.

The engine control unit (ECU, the computer that controls all of the electronic components

on your engine) "sees" the throttle valve open and increases the fuel rate in anticipation of

more air entering the engine. It is important to increase the fuel rate as soon as the throttle

valve opens; otherwise, when the gas pedal is first pressed, there may be a hesitation as

some air reaches the cylinders without enough fuel in it.

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Figure2 : Engine throttle valve [3]

(c) Idle speed control components:

An idle air control valve, also called an idle air sensor control motor, is an electrically

operated valve that controls the amount of air that bypasses the throttle plate in an engine

with a fuel injection system. This causes the idling speed of the engine to change as needed.

The computer in the vehicle that governs this function receives information from the air

sensor and determines the amount of air that the idle air valve allows to pass through it and

bypass the throttle plate.

Idle speed control can also be provided by direct action onto the throttle spindle.

Electrical solenoids or stepper motors are used for this method of control. The solenoids can

be single position or multi-position types and can be used for not only cold start and warm-

up control but also to open the throttle when high load systems, such as the air conditioner,

are switched on. [2]

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SENSORS USED IN EFI

ENGINE SPEED SENSORS :

The engine speed is measured by the use of Inductive Pulse Generators Most of the latest

systems have inductive pulse generators mounted close to, and responding to, a toothed

wheel attached to the crankshaft pulley or flywheel. There is an air gap between the toothed

wheel and the inductive generator. As the teeth pass the inductive generator, an alternating

electrical current is produced. The waves of the alternating current are used to measure

engine speed.

Figure4: Inductive Pulse Generator [2]

AIR FLOW METER:

This is required so as to determine the volume of the air entering the engine. A Vane Air

Flow Meter (VAF) is used for this purpose. The vane type air flow meter consists of an air

passage and damping chamber into which is fitted a fixed pair of flaps (or vanes). These

rotate on a spring-loaded spindle. The spindle connects to and operates a potentiometer

which is further connected to the ECU.

TEMPERATURE SENSORS:

Two temperature sensors are used mainly measure the air intake temperature and coolant

temperature.

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Figure5 : Coolant thermistor [2]

(a) Engine coolant temperature sensor

The engine coolant temperature sensor is a negative temperature coefficient (NTC)

thermistor. It is of a similar type to the air-temperature sensor. It is fitted into the water

jacket close to the thermostat or to the bypass coolant-circuit passages. The sensor measures

the engine coolant temperature and provides a signal voltage to the ECU. This is used for

cold start and warm-up enrichment as well as fast idle speed control through the idle-speed

control valve.

(b) Air intake temperature sensorIn order for the ECU to correctly calculate the required fuel for a correct mixture ratio, an

accurate figure for air mass is necessary. However, air volume and density are affected by

changes in temperature. As the temperature rises, the air density falls. The airflow, or

manifold absolute pressure measurement, therefore, must be corrected for temperature. The

sensor is a temperature-dependent resistor with a negative temperature coefficient (NTC).

EXHAUST GAS OXYGEN SENSORS:

The overall purpose of oxygen sensor is to maintain a close tolerance of the stoichiometric

ratio (14.7:1). The Greek letter () lambda is used as the symbol for a chemically correct air-

to-fuel ratio. This is the stoichiometric ratio of 14.7 parts of air to 1 part of fuel by mass.

This is why the sensor used to measure the oxygen content is called as Lamda Sensor. It is

fitted in the lower part of the exhaust stream and measures the oxygen content in it. More

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fuel is delivered when oxygen content is detected and less fuel when it is not. In this way, an

accurate fuel mixture close to the stoichiometric ratio is maintained.

Types are:

(a) Zirconia sensors

The zirconium dioxide, or zirconia, lambda sensor is based on a solid-state electrochemical

fuel cell called the Nernst cell. Its two electrodes provide an output voltage corresponding to

the quantity of oxygen in the exhaust relative to that in the atmosphere. An output voltage of

0.2 V (200 mV) DC represents a "lean mixture" of fuel and oxygen, where the amount of

oxygen entering the cylinder is sufficient to fully oxidize the carbon monoxide (CO),

produced in burning the air and fuel, into carbon dioxide (CO2). An output voltage of 0.8 V

(800 mV) DC represents a "rich mixture", one which is high in unburned fuel and low in

remaining oxygen.

Figure6 : Zirconia sensor [5]

(b) Titania sensor

A less common type of narrow-band lambda sensor has a ceramic element made of titania

(titanium dioxide). This type does not generate its own voltage, but changes its electrical

resistance in response to the oxygen concentration. The resistance of the titania is a function

of the oxygen partial pressure and the temperature

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THROTTLE POSITION SENSOR:

Two types of throttle-position sensor are used. Both are fitted to the throttle body and

operated by the throttle plate spindle. The two types are a throttle switch assembly and a

throttle potentiometer.

(a) Throttle switch assembly

A throttle switch assembly has two switches, one to indicate the closed throttle or idle

position and the other for the wide-open throttle position.

(b) Throttle potentiometer

A throttle potentiometer is a variable resistor with a rotary sliding contact. The sliding

contact is moved along the rotary resistance track to provide changes in voltage proportional

to the position of the throttle i.e the angle of the throttle plate. As the throttle opens, this

potentiometer circuit converts the mechanical movement of the throttle valve into a variable

voltage signal. The throttle potentiometer signals are used in the ECU for a number of

functions. At the closed throttle position, idle speed and deceleration fuel cut-off are

controlled. In the part-open throttle position (about 5 percent to 70 percent open) there is

normal operation with close control of fuel delivery and exhaust emissions. In the

wide-open throttle position (70 percent to 100 percent), full-load enrichment is provided.

MANIFOLD AIR PRESSURE SENSOR:

These sensors are used to monitor the vacuum in the intake manifold so that the mixture

strength can be adjusted according to the engine load. It can be said that it indirectly

measures the intake air volume i.e why those engines engines equipped with MAP sensors

do not have an Air Flow Meter. The MAP sensor is a pressure-sensitive component

consisting of a diaphragm and piezoelectric circuit. It can be a component fitted in

the engine compartment .It is connected by a rubber hose to the inlet manifold. The ECU

supplies a stabilized reference voltage, usually 5 V, to the sensor. This voltage is adjusted by

the MAP sensor electronics to provide an output signal proportional to the sensed absolute

atmospheric pressure. [2]

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ELECTRONIC CONTROL UNIT

At the heart of electronic fuel-injection (EFI) systems is the fuel control or electronic-controlunit (ECU) with a stored map of operating conditions. Electronic sensors provide data to the

microprocessor in the ECU, which calculates and sends the output signals to the system

actuators, which are the fuel pump, fuel injectors and idle air-control units. The ECU will

also switch some of the exhaust emission and auxiliary system components.

The electronic-control unit is an electronic microcomputer with a central processing

unit (CPU) or microprocessor. Inside the CPU are software programs that compare all

sensor-input data with a fixed map of operating conditions. It then calculates the required

output signal values for the injection valves and other actuators. Also called as Engine

Control Module (ECM).

Working of ECU

(i) Control of fuel injection: ECU will determine the quantity of fuel to inject

based on a number of parameters. If the throttle pedal is pressed further

down, this will open the throttle body and allow more air to be pulled into the

engine. The ECU will inject more fuel according to how much air is passing

into the engine. If the engine has not warmed up yet, more fuel will be

injected .

(ii) Control of ignition timing : A spark ignition engine requires a spark to initiate

combustion in the combustion chamber. An ECU can adjust the exact timing

of the spark (called ignition timing) to provide better power and economy.

(iii) Control of idle speed : Most engine systems have idle speed control built into

the ECU. The engine RPM is monitored by the crankshaft position sensor

which plays a primary role in the engine timing functions for fuel injection,

spark events, and valve timing. Idle speed is controlled by a programmable

throttle stop or an idle air bypass control stepper motor.

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WORKING OF EFI SYSTEM

Taking example forpetrol injection:

. Air enters through the air induction system where it is measured by the air flow meter. As

the air flows into the cylinder fuel is mixed into the air by the fuel injector.

. Fuel injectors are arranged in the intake manifold behind each intake valve. The injectors

are electrical solenoids which are operated by the ECU.

. The ECU pulses the injector by switching it on and off.

. When the injector is switched on, it opens spraying the atomized fuel at the back side of theintake valve.

. As the fuel is sprayed into the intake air stream, it mixes with the incoming air and

vaporizes due to the low pressure in the intake manifold. The ECU signals the injector to

deliver just enough fuel to achieve an ideal air/fuel ratio of 14.7:1.

. The precise amount of fuel delivered is a function of ECU control.

. This charge is introduced into the combustion during the suction stoke.

. The ECU determines the basic injection quantity based upon measured intake air volume

and engine rpm.

. Depending upon the engine operating conditions injection quantity will vary. The ECU

monitors variables such as coolant temperature, engine speed, throttle angle, and exhaust

oxygen content and makes injection corrections which determine final injection quantity.

DIESEL INJECTION:

Diesel being a less volatile fuel requires greater pressure for its atomization.The functioning

of a diesel EFI system is similar to that of petrol EFI system except the fact that air is

separately introduced into the combustion chamber during the suction stroke and diesel is

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introduced into the combustion chamber at around 15 to 25 before TDC during

compression stroke. [11]

Figure7 : Gasoline EFI system [11]

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Figure8: micro computer used in EFI system [11]

ADVANTAGES OF EFI

(1) Improvement in volumetric efficiency due to comparatively less resistance in the intake

manifolds which will cause less pressure losses. It eliminates majority of carburetor

losses and almost eliminates the requirement of manifold heating.

(2) Manifold wetting is eliminated due to fuel being injected into or close to the cylinder and

need not flow through the manifold.

(3) Atomization is independent of cranking speed and therefore starting will be easier.

(4) Highly accurate air/fuel ratio control throughout all engine operating conditions is

achieved.

(5) Excellent fuel economy , with improved emission controls.

(6) Improved cold engine startability and operation.

(7) Elimination of large number of mechanical components leads to reduction in

maintenance and provides a increased reliability.

(8) Superior throttle response and power. [3]

DISADVANTAGES OF EFI

(1) High maintenance cost.

(2) Difficulty in servicing and requires well skilled and professional workers who have

good knowledge of Electronic, Computers and Mechanical components.

(3) Possibility of malfunction of some sensors. [3]

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RECENT ADVANCEMENTS

(1) RDSO LUCKNOW:

It was the collaborative effort RDSO Lucknow and IIT

KANPUR that the first diesel locomotive equipped with

electronic fuel injection system (EFI) was flagged of from

RDSO lucknow on 14th September 2011. This retrofitment

is estimated to save 2% of fuel used as compared to the

conventional injection system.

Indian Railways consumes upto 2.5 billion litres of

fuel annually spending Rs 10,000 crores. This is going to

be a saving of Rs 200 Crores yearly. It involves a one time

investment. In the first phase RDSO has decided to equip

100 ALCO diesel engines with EFI system. [6]

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APPLICATIONS

(1)Royal Enfield Thunderbird 500

Figure9: Royal enfield [10]

It is a 499cc single-cylinder 4-stroke air-cooled Twin spark engine Fed by an advanced

Keihin electronic fuel injection system.

(2) Honda City ZX:

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Figure10: A 1497cc and EFI equipped car [7]

(3) Rolls Royce Phantom Series II

Figure11: Rolls Royce [8]

(4) F1 racing cars

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Figure12 : Racing car [9]

(5) All jet fighter planes

(6) Passenger planes

REFERENCES

[1] History of Fuel Injection by Frank Deluca.

[2] Automotive Technician Training - Tom Denton

[3] IC Engine by V Ganeshan.

[4]https://reader009.{domain}/reader009/html5/0421/5adb0f531b50d/5adb0f5f7bef0

[5] http://en.wikipedia.org/wiki/File:ZirconiaSensor.svg

[6] http://www.rdso.gov.in/

[7] http://www.autoinfoz.com/Honda/cars/Honda_City/Honda_City_Newspecification.html

[8] https://reader009.{domain}/reader009/html5/0421/5adb0f531b50d/5adb0f601e702.jpg

[9] http://www.autoblog.com/media/2012/13/F-1-racing-car.jpg

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[10] http://static.zigwheels.com/media/content/2012/Sep/rethunderbird500_1_560x420_560

420.jpg

[11] http://www.toyota.com/toyotaSearch/search?keyword=working+of+efi&locale=en

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