Automotive Systems course (Module 03) - Fuel Systems in Spark Ignition Internal Combustion Engines

11 de outubro de 2016 | 1

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Fuel systems – SI engines

Mário Alves ([email protected])

mailto:[email protected]


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Outline

• Objective of fuel systems

• Classification of fuel systems

• Evolution – technology, regulations

• Carburetor-based fuel systems

• Electronic Fuel Injection (EFI) systems

• Engine control – fundamentals

• Air/fuel mixture and combustion control subsystems

• Injection, idle speed and throttle position, fuel pump/pressure, ignition, supercharging

• Exhaust subsystem

• exhaust, EGR, oxygen sensors heating

• Other subsystems controlled by the engine ECU

• Radiator fan, Variable valves timing control, A/C compressor control, OBD/Check engine lamp

• Sensors

• Actuators


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• Main objective is to deliver fuel into the cylinders

• at proper timings (optimizing power)

• in correct amounts (for optimal A/F ratio, function of load, RPM,

engine temperature,…)

• in the right form (fuel atomization, for full combustion and lower

emissions)


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Classification of fuel systems (CI and SI)

Operating principle

ICE type single or multiple injectors

direct/indirect injection

technology

Mechanical SI (single point) indirect Carburetor

Diesel (multi-point) direct or indirect

Injection Pump (in-line or rotary), few hundred bars

Electronic SI SPI indirect in the throttle body, few bars

MPI indirect Fuel rail, few bars

direct Fuel rail, tens of bars

Diesel (multi-point) direct Fuel-rail or pump/unit-injection, hundreds to thousands of bars


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Classification of fuel systems

• Fuel system types

• “Mechanical” (increasingly electronically assisted)

• SI – mostly used until the dawn of “electronics” (< 1960)

• materialized by the “Carburetor”

• CI – still in use, but gradually changing to “common rail”

• materialized by the “Injection Pump” (in the figure)

http://what-when-how.com/automobile/distributor-type-injection-pump-automobile/
















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Classification of fuel systems

• Fuel system types

• “Electronic” (ECU-based) • Single-Point Injection (SPI) – Figure a)

• Aka “throttle-body injection”

• mostly used in low-cost small-sized SI engines

• Multi-Point Injection (MPI)

• Indirect (external) – Figure b)

• SI: injection is done upstream (the intake valves)

• Diesel: injection is done in a pre-chamber

• Direct (internal) – Figure c)

• pressure accumulator/common-rail systems (SI + most Diesel)

• pump/unit-injector systems (few Diesel)

http://www.intechopen.com/books/advances-in-internal-combustion-engines-and-fuel-

technologies/combustion-process-in-the-spark-ignition-engine-with-dual-injection-system

http://www.intechopen.com/books/advances-in-internal-combustion-engines-and-fuel-technologies/combustion-process-in-the-spark-ignition-engine-with-dual-injection-system





































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Evolution – fuel injection technology

http://engineringcorner.blogspot.pt/2011/10/next-generation-engines.html








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Evolution – European emission standards

https://www.ngk.de/en/technology-in-detail/lambda-sensors/basic-exhaust-principles/euro-standards/
















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Evolution – emission reduction vs. technologies

http://www.transportpolicy.net/index.php?title=EU:_Light-duty:_Emissions






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Carburetor-based fuel systems

• Basic carburetor operation

• air is drawn into the engine by the pumping action of the pistons (vacuum)

• the air accelerates as it passes through the venturi, causing a slight drop in pressure.

• this pressure drop pulls fuel from the float bowl (through a nozzle) into the throttle body

• it then mixes with air in a fine mist, which is distributed to the cylinders through the intake manifolds

• the choke valve enables the driver to control (enrich) the mixture, at cold start

http://cf.ydcdn.net/1.0.1.42/images/main/carburetor.jpg




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Carburetor-based fuel systems

• Main problems • Controlling fuel quantity accurately

• dependent on vacuum (not on fuel injection pressure/duration)

• insensitive to air temperature, pressure, humidity, engine temperature, RPM, throttle position,…

• Controlling fuel quantity in real-time

• delayed/reactive response

• Even delivery of air/fuel mixture

• across all cylinders (intake manifolds)

• Hard cold-start

• flooded carburetor…

• Fuel consumption

• 12-15 litres per 100 km was common

• Pollution

• high hydrocarbons in exhaust gases

https://s3.amazonaws.com/lowres.cartoonstock.com/transport-carburator-carburettor-flooded-

car_problems-roadside_rescue-mtun1380_low.jpg

https://s3.amazonaws.com/lowres.cartoonstock.com/transport-carburator-carburettor-flooded-car_problems-roadside_rescue-mtun1380_low.jpg















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Electronic fuel injection (EFI) systems

• EFI emerged due to • stringent exhaust emission regulations

• Increasing fossil fuel cost

• evolution of analog/digital electronics

• Basics • fuel pump compresses fuel

• fuel accumulator (rail) stores fuel

• electrically controlled injectors spray the fuel

• into intake manifold or

• combustion chamber

• ECU controls injection timing/duration for optimal engine control

• reduced emissions

• reduced fuel consumption

• maximized performance

http://www.gerrysap.com/efi.html




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EFI systems: Single-Point Injection (example)

• Mono-Jetronic

(1988–1995)

• one lambda sensor

• mechanical fuel

pressure regulator

• first generation

ignition system

• first generation on-

board diagnosis

http://www.jnc.cz/auto/monomotronic/Mono-Jetronic_blo ck_diagram.gif

http://www.jnc.cz/auto/monomotronic/Mono-Jetronic_blo





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EFI systems: Multi-Point Injection (example 1)

• D-Jetronic (1967–1976)

• "Speed-Density" fuel injection, i.e. there is no Air Flow Meter (AFM)

• air-mass flow is measured indirectly, by measuring intake air pressure (3),

temperature (not numbered), RPM (not in figure) and knowing cylinder

volume

http://www.aficionadosalamecanica.net/images-inyeccion/d-jetronic.jpg








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• L-Jetronic (1974–1989)

• L stands for Luft (air) flow meter (AFM)

• first generation ignition

• flap type AFM (11)

http://www.jagweb.com/aj6eng/42efi/page1.php




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• Motronic (1987-1998)

• integrates injection and

ignition (ECU controls both)

• fuel pressure accumulator

(fuel rail)

• more sensors proliferate

• second generation ignition

system

• intake air mass flow is

“directly” measured by air-

flow meter (12, flap type)

http://www.autobinary.co.za/motronic%20(1).jpg

http://www.autobinary.co.za/motronic (1).jpg

http://www.autobinary.co.za/motronic (1).jpg


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• Gasoline Direct Injection

http://www.gasitaly.com/f5direct




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• Toyota Computer-

Controlled System (TCCS)

• 1994 3VZ-E engine

http://enginepartsdiagram.com/1994-toyota-pickup-electronic-

fuel-injection-system-efi-diagram/

http://enginepartsdiagram.com/1994-toyota-pickup-electronic-fuel-injection-system-efi-diagram/



















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Fuel supply system example (E38/E39 – base for BMW 7 Series 1995-2001)

http://www.bimmerfest.com/forums/showthread.php?t=446032&page=3




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Fuel supply system example (E38/E39 – base for BMW 7 Series 1995-2001)


• Emphasis on the fuel tank




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Engine control - fundamentals

• Computer-controlled

• closed loop

• fault-tolerant

• real-time

• networked

• Controls

• fuel injection

• ignition

• ISC, EGR, …

• Composed of

• inputs (sensors)

• outputs (actuators)

• controller (ECU)

• network (e.g. CAN)

https://autoelectricalsystems.wordpress.com/2015/12/05/engine-

management-system-for-petrol-engines/

https://autoelectricalsystems.wordpress.com/2015/12/05/engine-management-system-for-petrol-engines/













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Engine control – DGI computer architecture (example 1)

• OEM = Renesas

http://www.renesas.eu/applications/automotive/powertrain/gasoline_direct/index.jsp




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Engine control – DGI computer architecture (example 2)

• OEM = Infineon

http://www.infineon.com/cms/en/applications/automotive/

powertrain/gasoline-direct-injection/

http://www.infineon.com/cms/en/applications/automotive/powertrain/gasoline-direct-injection/








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Outline

• Fuel systems classification

• SI fuel systems evolution





• Injection


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Fuel injection – algorithm (1)

• Base fuel volume

• engine RPM

• engine load

• Corrections

• exhaust oxygen

• water temp.

• accelerator pedal

• air temperature

• air pressure

• knock

• voltage

http://www.stealth316.com/2-fuelinjection.htm






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• Computation of fuel injection duration (volume/mass)

1. Baseline (target) fuel volume is computed according to engine load

• engine load = air mass flow divided by engine speed

• > air mass flow > injection duration

2. ECU selects closed- or open-loop mode based on throttle opening,

engine speed, vehicle speed, and fuel trim and air flow maps

• closed-loop: normal engine operation (A/F 14,7)

• open-loop: cold engine/strong accel/desaccelation (A/F < 14,7)

3. Corrections to the target fuel volume based on several parameters

(see flowchart) and an injector pulse width calculated

• all these computations must be made in a few milliseconds

• for an optimal (real-time) control of the engine







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• Example “fuel map” (for computing the base fuel volume)

• A/F ratio is optimized for best trade-off of power, fuel economy,

low emissions and knock prevention

• lower load & RPM leaner mixture (A/F > 14,7)

• higher load & RPM richer mixture (A/F < 14,7)

• ECU interpolates between values







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• Correction according to

coolant temperature

• fuel vaporization gets poorer for

colder engine (specially < 80 ºC)

• injection duration is increased

(A/F mix enrichened) for lower

temperatures







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intake air temperature

• a change in air temperature

changes the air density

• air density varies inversely

proportionally with air

temperature

• > temperature < density

• the colder the air, the denser it

becomes (more air mass for the

same air volume)

• more fuel must be injected to

keep the same air/fuel ratio







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atmosferic pressure

• air density varies proportionally

with air pressure

• > pressure > density

• air pressure varies inversely

proportionally with altitude

• < altitude > pressure

• lower altitude higher density

less pressure

• more fuel must be injected to

keep the same air/fuel ratio







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• Correction according to accelerator pedal • fuel is denser than air

• thus cannot move into the cylinder as quickly during engine acceleration

• so, a momentary lean condition may occur

• to compensate for this, the injection duration is increased

• extra injection pulses also may be delivered

• Injection duration is reduced during deceleration to improve fuel economy and emissions.







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charging system voltage

• current through the injector solenoid

needle valve is pulled up

• latency (dead time) between when

the current starts and the valve is

fully open

• injector valve speed depends on

applied voltage

• > voltage > current

< injector opening time

• injector must be activated

earlier for lower voltages and

later for higher voltages

• the actual opening period of

the injector remains the same







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oxygen in exhaust gases

• ECU uses UO2 in a feedback

(closed) loop

• to restrict A/F ratio to a narrow

range where catalyst is most

efficient (A/F = 14.7 1%)

• UO2 > 0,5 V rich mix

reduce fuel injection

• UO2 < 0,45 V lean mix

increase fuel injection







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Outline







• Injection, idle speed and throttle position


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Idle speed and throttle control

• Idle (or idling) state • an ICE is considered to be “idle” if the two following conditions apply

• the throttle pedal/grip is not depressed

• the engine is uncoupled to the drivetrain (either in neutral or with the clutch activated)

• Idle speed • is the rotational speed of the crankshaft at idle state

• usually measured in revolutions (rotations) per minute (RPM)

• Idle Speed Control (ISC) (aka Idle Air Control (IAC)) • idle speed must be optimized so that

1. the engine runs smoothly (without vibrations)

2. the engine generates enough power to operate ancillary devices

• alternator, A/C, water/oil pumps, power steering

3. fuel consumption is minimized (lowest RPM)


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• Typical idle RPM: • passenger-car = 600 – 1,000

• buses/trucks = 500 – 600

• motorcycles = 1000-1500

• Idle Speed Control can be • purely mechanical

• as in carburetor-based fuel systems

• ECU-based, through the control of either

• bypass ISC valve (in the intake manifold)

• inputting air upstream and outputting air downstream the throttle valve

• throttle valve

• Electronic Throttle Control (ETC), Throttle Actuator Control (TAC) or Throttle-By-Wire


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• Throttle (valve)

• valve that controls the flow of intake air

• by opening/closing of a rotating plaque (aka butterfly)

• integrated in the throttle body

http://mazdarx7.ugocapeto.com/Graphics/airintake.jpg

http://www.acuravigorclub.com/Timely-Topics/Timely0604.htm








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• Bypass ISC valve (aka idle air control (IAC) valve)

• controls the flow of intake air

• through a bypass to the throttle

• inputting air upstream the throttle

• outputting air downstream the throttle

• operating principles

• DC motor + worm drive

• step (servo) motor

• solenoid valve

http://www.stealth316.com/2-isc-iac.htm








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• Throttle (valve)

• its actuation can be

• purely mechanically-controlled (driven by a cable or rod)

• ECU-controlled (throttle-by-wire)

http://www.croberts.com/Throttle-control-

system-defects.htm

http://www.croberts.com/Throttle-control-system-defects.htm









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• Purely mechanically-controlled throttle

• up to the nineties, throttle opening/closing was directly (mechanically) driven by a cable connected to the driver’s accelerator pedal/grip

• driver pressing the accelerator = throttle opened

• driver not pressing the accelerator = throttle closed “idle” state

• ISC is purely mechanical, via the following mechanisms

• manual adjustment of air bypass (screw)

• manual adjustment of throttle position (cable; stop screw)

• automatic adjustment of air bypass according to coolant temperature (thermal valve)

http://www.autozone.com/repairinfo/repairguide/repairGu

ideContent.jsp?pageId=0900c15280088325

http://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c15280088325




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• ECU-controlled throttle

• throttle-by-wire has been emerging since the nineties

• BMW was the first vehicle manufacturer to offer electronic

throttle control in the 7-Series (1988)

• accelerator cable gradually replaced by ECU + throttle actuator

• either the driver is pressing the accelerator or not, the

throttle is ALWAYS controlled by the engine’s ECU

• driver not pressing the accelerator = “idle” state

http://www.aa1car.com/library/throttle-by-wire.htm








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Outline







• Injection, idle speed and throttle position, fuel

pump/pressure


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Fuel pump/pressure control

• Efficient fuel injection requires

• enough fuel flow (g/s)

• adequate fuel pressure (according to engine state)

• Main components

• fuel pump

• mechanically-driven

• by the crankshaft, through gears, chains or a toothed belt (often the timing belt)

• electrically-driven

• controlled by the ignition switch or by the engine ECU

• pressure regulator

• mechanical (diaphragm-controlled, not used nowadays)

• electrical (controlled by the engine ECU)

• fuel rail (if applicable)

• aka fuel accumulator or fuel distributor


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• Fuel systems can have 1 or 2 fuel pumps

• 1 pump fuel systems

• low pressure (few bars)

• used in ordinary SI engines (figure)

• high pressure (hundreds of bars)

• used in CI engines

• in-line

• distributor-type

• common-rail

http://12v.org/urs/engine_map/22618.phtml




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• Fuel systems can have 1 or 2 fuel pumps

• 2 pumps

• primary pump (low pressure)

• few bars

• secondary pump (high pressure)

• hundreds of bars

• used in

• CI unit-injector

• CI common rail

• SI direct injection (fig.)

http://www.motonic.co.kr/eng/02_product/product04.asp?leftMenu=4




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• Pressure regulators are crucial for optimizing fuel

injection, and can be

• purely mechanically-controlled

• diaphragm-controlled, not used nowadays

• guarantees a “constant” pressure differential between the

fuel pressure in the accumulator and the air depression in

the intake manifold

• electrically-controlled

• controlled by the engine ECU

• enables an optimized control of the fuel pressure in the fuel

accumulator, according to engine/load conditions


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• Mechanically-controlled fuel pressure regulator

• guarantees “constant” pressure differential between

• fuel pressure (in the “rail”) and

• intake air depression (intake manifold)

• operation

• throttle opens (left figure)

1. intake air pressure increases

2. return valve closes

3. no fuel return to tank

4. fuel pressure increases in “rail”

• throttle closes (right figure)

1. intake air pressure decreases (vacuum)

2. return valve opens

3. fuel returns to tank

4. fuel pressure decreases in “rail”

http://www.troublecodes.net/pcodes/p0300/

1 bar = 14,7 PSI

(average air pressure at sea level




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• Mechanically-controlled fuel pressure regulator

http://www.rx7club.com/single-turbo-rx-7s-23/frp-fuel-pressure-regulator-vacuum-line-why-882703/


























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• ECU-controlled fuel pressure regulator (CI engine)

• Pressure Control Valve (PCV)

https://www.dieselnet.com/tech/diesel_fi_common-rail_control.php






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• ECU-controlled fuel pressure regulator (SI GDI engine)

• PCV is integrated with high-pressure fuel pump

http://www.slideshare.net/GLADIADORVASCO/automotive-fuel-and-emissions-control-

systems-60582784

http://www.slideshare.net/GLADIADORVASCO/automotive-fuel-and-emissions-control-systems-60582784















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Ignition

• (ignition will be addressed in a separated module)

https://autoelectricalsystems.wordpress.com/2015/12/05/engine-

management-system-for-petrol-engines/














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Outline







• Injection, idle speed and throttle position, fuel pump/pressure,

ignition, supercharging (forced air induction)


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Supercharging

• Supercharging = forced air induction

• compress intake air increase air mass (flow)

• power output is increased for a given displacement and engine speed

• Types

• mechanically-driven –supercharger

• directly driven by crankshaft (belt)

• exhaust-gas-driven – turbocharger

• driven by exhaust gases (turbine)

• hybrid (mechanically-driven) – twin-charger

• supercharger + turbocharger

• hybrid (electrically-driven) – electric supercharger

• electric motor/generator supporting the turbo/supercharger


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Supercharging – turbocharger

• waste gate allows exhaust air to bypass the turbine

(modulated by boost controller)

• pop-off valve emergency pressure release (prevents

excessive air pressure into combustion chamber)

• blow-off valve prevents back-pressure in the

compressor when throttle valve is abruptly shut

http://atlanticz.ca/zclub/techtips/turbo/




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Supercharging – supercharger

http://www.diamondp.com/kb_results.asp?ID=8

• Driven by the crankshaft through belt + pulley

• no turbo lag but requires some engine power

http://www.americanmuscle.com/power-adders-for-s550-mustangs.html














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Supercharging – twin-charger

• < RPM supercharger

• > RPM turbocharger

http://prettymotors.com/twincharging-engine/






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Supercharging – electric turbocharger

• Series-hybrid turbocharger

• turbine-motor/generator-compressor

• < RPM

• Battery motor compressor

• > RPM

• turbine generator battery

• replacing the alternator?

http://www.aeristech.co.uk/full-electric-turbocharger-technology/










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Supercharging – electric supercharger

• Drive is fully electrical

• Particularly good for low RPM

• when engine power is low

• Tens of kW hundreds of A

• powerful alternator


http://blog.caranddriver.com/blowing-your-way-to-savings-how-electric-superchargers-boost-mpg/






























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Supercharging – hybrid supercharging

• < RPM supercharger

• > RPM turbocharger

http://www.autocar.co.uk/car-news/motoring/audi-reveals-

electric-turbocharger-technology

http://www.autocar.co.uk/car-news/motoring/audi-reveals-electric-turbocharger-technology













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Outline








• Injection, idle speed and throttle position, fuel pump/pressure,

ignition, supercharging




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Exhaust system

• Objectives

• convey exhaust gases out of the engine

• reduce exhaust heat, noise and pollutant emissions, affecting

engine power as little as possible

• Main components

• exhaust manifold to draw exhaust gases out of the cylinders

• turbocharger (if applicable) to increase engine power

• catalytic converter to reduce pollutant emissions

• muffler(s)/silencer(s) to reduce noise

• exhaust pipe(s) to link the above components in order to

convey and expel gases at a convenient point in the vehicle


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Exhaust system

• Exhaust system outlook – SI engine

http://hdabob.com/exhaust.htm




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Exhaust gas recirculation (EGR)

• recirculates part of the exhaust gases into the intake

• 5-15% in SI engines

• up to 50% in CI engines

• EGR aim is to meet emissions standards

• most ICE (SI and CI) must have EGR

• some modern ICE do not need EGR

• e.g. use selective catalytic reduction (SCR) to reduce NOx


Sistemas A

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• EGR leads to

• < oxygen admitted

• < peak in-cylinder temperatures

• < NOx emissions

• < engine power

• > particulate emissions (CI)

• NOx reduction efficiency

• < for > oxygen %

• a given NOx reduction requires

• < EGR at high loads

• > EGR at low loads

https://www.dieselnet.com/tech/engine_egr_performance.php




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• EGR system can be low or high-pressure and includes

• ECU-controlled EGR valve

• EGR cooler (specially for SI engines)

http://denso-europe.com/denso-develops-it-first-egr-cooler-for-gasoline-engines/

http://www.ni.com/white-paper/13516/en/#





















http://www.ni.com/white-paper/13516/en/





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Outline








• Injection, idle speed and throttle position, fuel pump/pressure, ignition, supercharging



• Other subsystems controlled by the engine ECU

• Radiator fan, Variable valves timing control, A/C compressor control, OBD/Check engine lamp

• Sensors

• Actuators


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Engine control - sensors

• (sensors will be addressed in a separated module)

• IG/STA switch, neutral switch, A/C switch

• THW, THA, MAP, TPS

• Air Flow Meter

• Knock, RPM,

• Crankshaft/cam shaft position

• Fuel pressure/temperature

• Oxygen sensors (pre/post catalyzer)

• Alternator output voltage


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Engine control - actuators

• (actuators will be addressed in a separated module)

• Fuel pump

• Radiator fan

• igniters

• Injectors

• Throttle control

• ISC

• EGR control

• Fuel pressure regulator

• OBD/Check engine lamp

• Oxygen sensors heating

• Variable valves timing control

• A/C compressor control

Engineering

Automotive Systems course (Module 03) - Fuel Systems in Spark Ignition Internal Combustion Engines