Fuel Injector: Description and Operation

NOTE: The fuel injector is driven by its solenoid coil based upon the ECM output signal. There is some delay called "Ineffective injection time," where no fuel is provided, between the ECM signal and valve action. Since ineffective injection time depends on the battery voltage, the ECM takes voltage information to compensate for fuel injection time.

Synchronous Injection At Lower Than 4000 RPM:

In this system, the ECM controls the on-time (length of pulse) and timing of the fuel injection from the fuel injector into the throttle body according to the signals from the various sensors so that suitable air/fuel mixture is supplied to the engine in each driving condition. There are two types of injection timing. One is "synchronous injection" in which injection is synchronous with the ignition signal (or signal from crank angle sensor) and the other is "asynchronous injection" in which injection takes place independently of the ignition signal (or signal from crank angle sensor). The factors to determine the injection time are the basic injection time which is calculated on the basis of the engine speed and the intake manifold pressure (amount of the intake air) and various compensations which are determined according to the signals from various sensors that detect the state of the engine and driving conditions.

Fuel Injector Cross-Section:

It is an electromagnetic type injection nozzle which injects fuel in the throttle body bore according to the signal from the ECM. When the solenoid coil of the injector is energized by the ECM, it becomes an electromagnet and attracts the plunger. At the same time, the needle valve which is incorporated with the plunger opens and the injector which is under the fuel pressure injects fuel in conic dispersion. As the stroke of the needle valve of the injector is set constant, the amount of fuel injected at one time is determined by the length of time during which the solenoid coil is energized (injection time).