Fuel Injection Operation: Overview

Fuel Injection Operation
The Powertrain Control Module (PCM) controls the amount of fuel the fuel injector supplies to each cylinder by controlling the ON time (length of pulse) of each individual injector. The delivery timing of the fuel into the cylinder head intake port by the fuel injector is controlled by the PCM. The timing and pulse of the fuel injectors is carefully calculated with inputs from the various sensors, so that a suitable air/fuel mixture is supplied to the engine for every driving condition.

There are two types of injection timing. One is Synchronous Injection, in which the injection is synchronous with the ignition signal (or the signal from the Camshaft Position [CMP] sensor). The other is Asynchronous Injection, in which injection takes place independently of the ignition signal (or the signal from the CMP Sensor).

The PCM first calculates the correct timing of the fuel injectors by factoring the engine speed and the air volume together. Then the PCM applies certain compensations that are based on the information provided by various sensors which detect the state of the engine and the current driving conditions.

Synchronous Injection
When starting the engine, the fuel injectors inject the fuel simultaneously and synchronously at every CMP sensor signal. When the engine is starting at a cold state, the amount of fuel is determined by the Engine Coolant Temperature (ECT) sensor and is divided and injected.

Once the engine is running, the fuel injection occurs in a cylinder only when it is in the exhaust stroke. The PCM detects the compression stroke of the No. 1 cylinder through the CMP sensor signal.

Asynchronous Injection
Whenever a change in the throttle valve opening exceeds a specified value (as determined by the PCM), additional fuel is injected simultaneously into the cylinders which are in the intake and exhaust strokes. This is in addition to the above synchronous injection and is not based on the ignition signal.