Fuel Injection Operation

Parameter Diagram For Fuel Injection Control System:

Synchronous Injection:

Asynchronous Injection:

DESCRIPTION
In this system, the Powertrain Control Module (PCM) controls the "ON" time (length of pulse) and timing of the fuel injection from the fuel injector into the Throttle Body Fuel Injection (TBI) unit according to the signals from the various sensors so that a suitable air/fuel mixture is supplied to the engine in each driving condition.

INJECTION TIMING
There are two types of injection timing. One is "Synchronous Injection" in which injection is synchronous with the ignition signal (or signal from Camshaft Position (CMP) sensor and the other is "Asynchronous Injection" in which injection takes place independently of the ignition signal (or signal from Camshaft Position (CMP) 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.

Synchronous Injection
Normally, the fuel injector injects fuel at every ignition signal (or at every signal from the Camshaft Position [CMP] sensor). But when the Engine Coolant Temperature (ECT) is low immediately after the engine starts, the injection time for one ignition cycle is divided into two cycles and injection takes place accordingly.

Asynchronous Injection
When the throttle valve is opened from its idle position, the Powertrain Control Module (PCM) pulses the injector to inject additional fuel in addition to synchronous injection independently of the ignition signal (or signal from the Camshaft Position [CMP] sensor).

In order to improve starting performance, enriching compensation at start is carried out. For a certain time after the engine is started, air/fuel mixture is slightly enriched to stabilize the engine speed. The amount of compensation varies depending on the Engine Coolant Temperature (ECT) sensor.