Electronic Gasoline Injection

In electronic fuel injection (FFI) system the controller is an electronic control module (E.C.M) or electronic control unit (E.C.U). It is also called on board computer because it is on board the car. (Also called Electronic Control Module).

Various components of the engine and fuel system send electric signals to the E.C.M. The E.C.M continuously calculates how much fuel to inject. It then opens the fuel injectors so the proper amount of fuel sprays out to produce the desired air fuel ratio. Sensors that report to the E.C.M include.

1. Engine speed

2. Throttle position

3. Intake manifold vacuum or manifold absolute pressure (MAP)

4. Engine coolant temperature

5. Amount and temperature of air entering engine

6. Amount of oxygen in exhaust gas

7. Atmospheric pressure

The ECM continuously receives all this information or data. The ECM checks this data with other data stored in look up tables in its memory. Then ECM decides when to open the injectors and for how long. The opening and closing of an injector to remain open is the injector pulse width. Suppose if more fuel is needed then the ECM increases the pulse width.