Why we use Electronic Fuel Injection?

Allows precise and fast control of fuel injected. By control of the ‘on-time’ period of the solenoid operated injectors (spray nozzle) and plunger. Delivery pipe fuel pressure is maintained constant by a fuel pressure regulator. Opening and closing times of between 0.5 and 1 ms. Engine operating speed of 6000 rpm (10 ms revolution time) Injector on-time can be controlled between 1 and 10 ms.

 EFI Gasoline Engine Components : 

FuelInjector Fuel Pump Fuel Pressure Regulator Engine Control Unit Wiring Harness Various Sensors like, 1.EGO Sensor 2.Crankshaft Position Sensor 3.Mass Airflow Sensor 4.Manifold Absolute Pressure Sensor

Block Diagram of EFI

Working Of EFI System

An ECU receives electrical Signals in form of Voltage and Current from various Sensors. It then uses the stored data to operate the injectors, ignition system and other Engine related devices. As a Result of it, less unburned fuel leaves the engine as emission. Due to it, Vehicle gives better Mileage. The Fuel Injector in EFI system is nothing but a Fuel Valve.

When the fuel injector is not energized, spring pressure makes the injector to remain closed and No fuel will enter the Engine. When Computer Sends the signal through the injector Coil, the magnetic field attracts the injector Armature. Fuel then spurts into the intake Manifold. The Injector pulse width is an indication of the period for which each injector is energized and kept open. The Computer decides and control the injector pulse width Based on the signal received from the various sensors. Under full load, the computer will sense a wide open throttle, high intake manifold pressure and high inlet air flow.

The ECU then increase the injector pulse width to enrich the mixture which will enable the engine to produce high power. Under low load condition, the ECU will shorten the pulse width by which the injectors are kept in the closed position over a long period of time. Because of this, Air-fuel mixture will become leaner and will result in better fuel Economy.


Improvement in volumetric efficiency due to comparatively less resistance in the intake manifolds which will cause less pressure losses. Manifold wetting is eliminated due to fuel being injected into or close to the cylinder. Atomization of fuel is independent of cranking speed and therefore starting will be easier. Better Atomization and Vapourization will make the Engine less knock Prone. Formation of ice on the throttle plate is eliminated.

Dis-Advantages :

Higher maintainance cost.

Difficultyin servicing.

Possibility of Malfunction of some sensors.

Complexity of System is Higher.




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