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Electronic Fuel InjectionElectronic Fuel Injection

Roger BortignonRoger Bortignon

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Electronic Fuel InjectionElectronic Fuel Injection

• during the late 1970’s and early 1980’s, government imposed minimum fuel during the late 1970’s and early 1980’s, government imposed minimum fuel mileage standards and tougher pollution control standards meant the end of the mileage standards and tougher pollution control standards meant the end of the carburetorcarburetor

• Electronic Fuel Injection (EFI), was developed to help manufacturers build vehicles Electronic Fuel Injection (EFI), was developed to help manufacturers build vehicles that use less fuel, run cleaner and perform betterthat use less fuel, run cleaner and perform better

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What is EFI?What is EFI?

• EFI uses a computer called a EFI uses a computer called a Powertrain Control ModulePowertrain Control Module (PCM) to determine how (PCM) to determine how much fuel the engine needs much fuel the engine needs

• the computer turns on a fuel injector which sprays fuel, under pressure, into the the computer turns on a fuel injector which sprays fuel, under pressure, into the intake manifold or directly into the cylinderintake manifold or directly into the cylinder

Hey Roger, this new technology is amazing!Hey Roger, this new technology is amazing!

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3 main types of fuel injection…3 main types of fuel injection…

1)1) Throttle body injection (TBI)Throttle body injection (TBI)• uses 1 or 2 injectors mounted on top of the throttle (fig. a)uses 1 or 2 injectors mounted on top of the throttle (fig. a)• performs better than a carburetorperforms better than a carburetor• unequal fuel distribution with some condensationunequal fuel distribution with some condensation• looks similar to a carburetor (fig. b)looks similar to a carburetor (fig. b)• low manufacturing costslow manufacturing costs• not as common today (used a lot in the 1980s)not as common today (used a lot in the 1980s)

fig. a

fig. b

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3 main types of fuel injection…3 main types of fuel injection… 2) 2) Multi-port or multi-point injection (MPFI)Multi-port or multi-point injection (MPFI)

• uses 1 injector for each cylinderuses 1 injector for each cylinder

• much more common than TBImuch more common than TBI

• delivers the fuel more precisely than TBIdelivers the fuel more precisely than TBI

• more complex and costly compared to TBImore complex and costly compared to TBI

• intake manifold only delivers air so it can be designed for max. air flowintake manifold only delivers air so it can be designed for max. air flow

• improves low speed torqueimproves low speed torque

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3 main types of fuel injection…3 main types of fuel injection…

• 3) 3) Direct injection (newest design) injects the fuel directly into the combustion Direct injection (newest design) injects the fuel directly into the combustion chamberchamber

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How EFI WorksHow EFI Works

InputInput Engine sensorsEngine sensors

ProcessingProcessing OutputOutput Computer Computer Fuel quantityFuel quantity

Idle speedIdle speed Spark timingSpark timing

Emission controlsEmission controls

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Input SectionInput Section

• these sensors provide engine information to the PCM…these sensors provide engine information to the PCM…

engine speed sensor engine speed sensor

throttle position sensorthrottle position sensor

coolant temperature sensorcoolant temperature sensor

air temperature sensorair temperature sensor

engine load sensorengine load sensor

knock (detonation) sensorknock (detonation) sensor

oxygen sensoroxygen sensor

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Input Section – Engine SpeedInput Section – Engine Speed

• engine speed, measured in RPM’s, is provided to the PCM engine speed, measured in RPM’s, is provided to the PCM by either…by either…

the distributor’s pick-up coil (the distributor’s pick-up coil (vehicles with vehicles with distributorsdistributors) or… ) or…

crankshaft position sensor (crankshaft position sensor (used on distributor-less & used on distributor-less & direct ignitiondirect ignition))

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Input Section – Throttle PositionInput Section – Throttle Position

• throttle position sensor (TPS) tells the PCM how much pressure the driver is throttle position sensor (TPS) tells the PCM how much pressure the driver is putting on the throttleputting on the throttle

• TPS is a variable resistorTPS is a variable resistor

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Input Section – TPSInput Section – TPS

• a 5 volt signal is sent to the TPS. A return signal is sent back to the PCM a 5 volt signal is sent to the TPS. A return signal is sent back to the PCM

that corresponds with throttle position.that corresponds with throttle position.

• idle: ≈ .5 voltidle: ≈ .5 volt

• ½ throttle: ≈ 2.5 volts½ throttle: ≈ 2.5 volts

• wide open throttle ≈4.5 voltswide open throttle ≈4.5 volts

• PCM interprets these return voltages as specific throttle positions. PCM interprets these return voltages as specific throttle positions.

• PCM can then adjust the quantity of fuel needed accordingly.PCM can then adjust the quantity of fuel needed accordingly.

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TPS & PCM WiringTPS & PCM Wiring

• throttle position determines what portion of the 5 volt signal is at the PCM’s throttle position determines what portion of the 5 volt signal is at the PCM’s signal terminalsignal terminal

PCM

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Input Section – Engine TemperatureInput Section – Engine Temperature

• a coolant temperature sensor (CTS) is used to provide the PCM with the a coolant temperature sensor (CTS) is used to provide the PCM with the temperature of the coolanttemperature of the coolant

• the PCM can then inject more fuel the colder the engine is or less fuel as the the PCM can then inject more fuel the colder the engine is or less fuel as the engine warms up engine warms up

• the CTS is a temperature sensitive resistor (thermistor). As the temperature the CTS is a temperature sensitive resistor (thermistor). As the temperature increases, its resistance decreasesincreases, its resistance decreases

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Input Section – Air TemperatureInput Section – Air Temperature

• an air temperature sensor is used to provide the PCM with the temperature of the an air temperature sensor is used to provide the PCM with the temperature of the air entering the intake manifoldair entering the intake manifold

• the PCM can then inject more fuel the colder the engine is or less fuel as the engine the PCM can then inject more fuel the colder the engine is or less fuel as the engine warms upwarms up

• the air temperature sensor is a temperature sensitive resistorthe air temperature sensor is a temperature sensitive resistor as the temperature increases, its resistance decreasesas the temperature increases, its resistance decreases

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Input Section – Measuring Engine Load #1Input Section – Measuring Engine Load #1

• a a manifold absolute pressuremanifold absolute pressure sensor (MAP sensor) senses engine vacuum and sensor (MAP sensor) senses engine vacuum and uses this signal as an indicator of the engine loaduses this signal as an indicator of the engine load

• light engine load = higher vacuum = lower manifold pressurelight engine load = higher vacuum = lower manifold pressure• heavy engine load = lower vacuum = higher manifold pressureheavy engine load = lower vacuum = higher manifold pressure

• PCM responds by injecting more fuel into the engine during heavy loads, or less PCM responds by injecting more fuel into the engine during heavy loads, or less fuel at light loadsfuel at light loads

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Input Section – Measuring Engine Load #2Input Section – Measuring Engine Load #2

• another way to measure engine load is to another way to measure engine load is to

measure how much air is flowing into the enginemeasure how much air is flowing into the engine

• mass airflow sensormass airflow sensor (MAF) “tells” the (MAF) “tells” the

computer how much load is being placed on the computer how much load is being placed on the

engineengine

• MAF measures airflow into the engine in MAF measures airflow into the engine in

grams/secondgrams/second

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Input Section – Measuring Engine Load #3Input Section – Measuring Engine Load #3

• air flow can also be measured with an air flow can also be measured with an air flow meterair flow meter• uses a moveable flapuses a moveable flap

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Input Section – Spark KnockInput Section – Spark Knock

• knock sensor can detect detonation & PCM will respond by retarding the ignition knock sensor can detect detonation & PCM will respond by retarding the ignition timingtiming detonation is combustion of the fuel that wasn’t initiated by the spark plugdetonation is combustion of the fuel that wasn’t initiated by the spark plug this can be caused by excessive heat, carbon build-up or low octane fuelthis can be caused by excessive heat, carbon build-up or low octane fuel

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Input Section – Oxygen SensorInput Section – Oxygen Sensor

• the key to EFI’s ability to provide excellent fuel economy & low emissions is the the key to EFI’s ability to provide excellent fuel economy & low emissions is the oxygen sensoroxygen sensor (O2 sensor) (O2 sensor)

• the O2 sensor “tells” the PCM if the air-fuel mixture is too rich or too lean. PCM the O2 sensor “tells” the PCM if the air-fuel mixture is too rich or too lean. PCM then adjusts the AFM to keep it at the ideal ratio of 14.7:1then adjusts the AFM to keep it at the ideal ratio of 14.7:1

Tech Tip:Tech Tip: too rich means too much fueltoo rich means too much fueltoo lean means too little fuel too lean means too little fuel

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How does the O2 sensor do that?How does the O2 sensor do that?

• the O2 sensor screws into the exhaust pipe the O2 sensor screws into the exhaust pipe

• as the exhaust gases leave the engine, the O2 sensor compares oxygen in the atmosphere to as the exhaust gases leave the engine, the O2 sensor compares oxygen in the atmosphere to oxygen left in the exhaust gasesoxygen left in the exhaust gases

• if there is if there is little oxygenlittle oxygen left over, this means the mixture is left over, this means the mixture is too richtoo rich

• if there is if there is lots of oxygenlots of oxygen left over, then the mixture is left over, then the mixture is too lean too lean

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O2 Sensor Communication with the PCMO2 Sensor Communication with the PCM

• if the mixture is too rich = little oxygen is left over in the exhaust gasesif the mixture is too rich = little oxygen is left over in the exhaust gases O2 sensor produces ≈ 1 voltO2 sensor produces ≈ 1 volt

• if the mixture is too lean = lots of oxygen left over in the exhaust gasesif the mixture is too lean = lots of oxygen left over in the exhaust gases O2 sensor produces a low voltage ≈ .1 voltO2 sensor produces a low voltage ≈ .1 volt

• if the mixture is perfect (14.7:1), then the O2 sensor will produce .5 voltif the mixture is perfect (14.7:1), then the O2 sensor will produce .5 volt

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Output SectionOutput Section

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Output Section – Fuel DeliveryOutput Section – Fuel Delivery• once the PCM has received all the data from the input sensors, it then decides how once the PCM has received all the data from the input sensors, it then decides how much fuel to give the engine by varying how long the injector is turned onmuch fuel to give the engine by varying how long the injector is turned on

• injector on-time is called pulse width injector on-time is called pulse width (measured in milliseconds)(measured in milliseconds)

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Output Section – Idle Speed ControlOutput Section – Idle Speed Control

• the PCM is also responsible for controlling the idle speed of the engine with an the PCM is also responsible for controlling the idle speed of the engine with an idle speed motor…idle speed motor…

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PCM Output ControlPCM Output Control

• in addition to fuel quantity & idle speed control, the PCM also controls in addition to fuel quantity & idle speed control, the PCM also controls emission control devicesemission control devices we’ll discuss these after spring breakwe’ll discuss these after spring break

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Fuel Delivery SystemFuel Delivery System• a fuel pump draws fuel from the tank and pressurizesa fuel pump draws fuel from the tank and pressurizes• the fuel pump and fuel pressure regulator work together to maintain…the fuel pump and fuel pressure regulator work together to maintain…

TBI injection operates at lower pressures ≈ 15psi (using an electric fuel pump)TBI injection operates at lower pressures ≈ 15psi (using an electric fuel pump)some multiport pressures are higher than 35psi (using an electric fuel pump)some multiport pressures are higher than 35psi (using an electric fuel pump)direct injection can be in the 400 – 1500psi range (using a mechanical fuel pump)direct injection can be in the 400 – 1500psi range (using a mechanical fuel pump)

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Electric Fuel PumpElectric Fuel Pump

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Returnless Fuel Supply System Returnless Fuel Supply System

• used since the mid 90’sused since the mid 90’s• uses an in-tank fuel pump & pressure regulator moduleuses an in-tank fuel pump & pressure regulator module• reduces fuel evaporative lossesreduces fuel evaporative losses• PCM can vary fuel supply by modifying fuel pump pulse widthPCM can vary fuel supply by modifying fuel pump pulse width

Return-less-typeReturn-type

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Direct Injection Fuel SupplyDirect Injection Fuel Supply

• direct injection engines use an engine driven, high pressure mechanical fuel direct injection engines use an engine driven, high pressure mechanical fuel pump…pump…

• 35psi, as is found on port injection is insufficient for direct injection35psi, as is found on port injection is insufficient for direct injection

• direct injection pressures must overcome compression pressuresdirect injection pressures must overcome compression pressures

45 sec.

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Gasoline Fuel InjectionGasoline Fuel Injection

• optimal (more better) way of delivering fuel to a spark ignition engine when optimal (more better) way of delivering fuel to a spark ignition engine when compared to carburetorscompared to carburetors

more exact control of fuel deliverymore exact control of fuel delivery

AFM ratio better matched to the engine working conditionsAFM ratio better matched to the engine working conditions

better fuel economybetter fuel economy

fewer emissionsfewer emissions

less cylinder wear (less chance of fuel washing oil off cylinder)less cylinder wear (less chance of fuel washing oil off cylinder)

better performance (driveability) better performance (driveability)

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Electronic Throttle Control - AKA Drive-by-wireElectronic Throttle Control - AKA Drive-by-wire• throttle cable is eliminatedthrottle cable is eliminated• PCM controls air flow into engine – not the driverPCM controls air flow into engine – not the driver• TPS is still usedTPS is still used• PPedal edal PPosition osition SSensor (ensor (PPSPPS) added) added• DC servo motor opens/closes throttle plateDC servo motor opens/closes throttle plate

PPS