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Principle and Working of Electronic Fuel Injection System

12.08.2015 · Posted in cars

All modern vehicles are provided with a fuel injection system to convey fuel to the engine while reducing the amount of harmful emissions that a vehicle emits off. Modern automobiles use electronic fuel injection (EFI) in their fuel delivery system in order to increase the efficiency. The EFI engines run more smoothly, with lower emissions and fuel consumption.

*Principle of EFI
*EFI is an indirect, pressurized injection system with injectors operated by a solenoid.
*In a multi-point injection system, each intake manifold has an injector. An electronic control unit helps to process the data from various sensors to optimize the fuel mixture.

Working of EFI: Fuel injection systems are comprised of a complex array of components that work together to supply fuel to the vehicle’s engine. Electronic fuel injection system is controlled by an electronic control unit.

*Controlling fuel mixture
*In order to accelerate one should push the gas pedal, accelerate pedal position (APP) sensor sends signal to the EFI system. EFI then commands to open the throttle. EFI takes information from the throttle position sensor and APP till it has reached the desired position set by driver.
*Amount of air flow entering the throttle body is determined by either a mass air flow (MAF) sensor or a manifold absolute pressure (MAP) sensor and then the information is sent to the EFI. EFI then uses this information to inject amount of fuel.
*MAF or MAP and throttle position sensor readings are continuously read by a computer in order to know the amount of fuel being injected.
*EFI system also uses an oxygen sensor to know the amount of oxygen present in the exhaust.

*Controlling idle
*EFI system uses sensor to read the position of a crankshaft. It sends fuel based upon the speed of the crankshaft which in turn depends on the load of the engine. For example, when we shift vehicle to drive, the speed of the crankshaft decreases. The crankshaft sensor will communicate this information to the EFI, thus opening the throttle and adding more fuel to overcome the engine load.
*In the initial stage the engine may have higher revolutions, this is due to the presence of a temperature sensor which detects the temperature of engine. If the sensor detects less temperature, it will set higher idle threshold to raise the temperature of engine.

*Controlling ignition timing
*In modern vehicles, ignition systems have a coil located on each individual spark plug.
*The data from all the sensors is sent to the EFI system which determines the appropriate coil to be fired. EFI continuously receives information from the crankshaft sensor to optimize spark timing.
*Knocking is a phenomenon in engine which may occur due to combustion of fuel-air mixture at inappropriate time. EFI system uses a knock sensor and retards the ignition timing to make knock less-severe.

*Controlling valve timing
*This is seen in automobiles with variable valve timing which helps to enable the engine to achieve optimal efficiency at varying speeds.
*The sensors present in the engine give information regarding the valve timing to the EFI. This is a forward signal and EFI sends feedback to the valve sensor on when to open depending on the fuel supply or exhaust gases.

EFI systems are crucial to the operation of any vehicle, as it provides with required fuel to the engine. The various parts of the EFI analyze the conditions inside the vehicle and adjust the conditions that are necessary to operate the vehicle efficiently.

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