Fuel Delivery Modes

FUEL INJECTION OPERATION
In this system, the ECM controls the "ON" time (length of pulse) and timing of the fuel injection from the fuel injector into the cylinder head intake port according to the signals from the various sensors so that a suitable air/fuel mixture is supplied to the engine in each driving condition.

FUEL 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 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 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
When starting the engine all four fuel injectors inject fuel simultaneously and synchronously at every Camshaft Position 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, fuel injection occurs in a cylinder only when it is in the exhaust stroke. The ECM detects the compression stroke of the No. 1 cylinder through the CMP sensor signal. On the basis of this, it controls sequential fuel injection from each injector of cylinders No. 1, 3, 4 and 2 in that order.

ASYNCHRONOUS INJECTION
Whenever a change in throttle valve opening exceeds a specified value (determined by the ECM), fuel is injected into the cylinders which are in the intake and exhaust strokes simultaneously and in addition to the above synchronous injection.

ENGINE STARTING ENRICHMENT
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.

ENGINE WARM-UP ENRICHMENT
When the engine is cold, additional fuel is added to ensure good driveability until the engine coolant temperature reaches the specified level. The amount of air/fuel mixture is decreased as the engine coolant temperature rises.

ACCELERATION ENRICHMENT
During acceleration the fuel injector's pulse is lengthened to add more fuel. This ensures a smooth stable acceleration of the engine. The additional fuel is added based on engine coolant temperature.

POWER ENRICHMENT
To provide maximum power during high engine load driving conditions, the air/fuel mixture is enriched when the throttle valve opening is larger than specified as determined by the ECM.

SYSTEM VOLTAGE COMPENSATION
A power voltage drop delays the mechanical operation of the fuel injector. The actual injection time becomes shorter for the time that electricity is supplied to the fuel injector. To compensate for this, the fuel injector pulse is lengthened.

BASE AIR/FUEL RATIO COMPENSATION
The air/fuel ratio may vary due to such factors as variation in each engine itself and aging. To compensate for such variation, feedback compensation is used and base air/fuel mixture ratio is adjusted to a proper level to maintain optimum air/fuel ratio.

FUEL CUTOFF
Fuel injection stops (with operation of the fuel inject prevented) when decelerating (i.e., when the throttle valve is at idle position and the engine speed is high), so that unburned gas will not be exhausted and injection starts again when above conditions are not met.

The fuel injection also stops when the engine speed exceeds 6,800 RPM to prevent overrun which affects the engine adversely, and it starts again when the engine speed reduces to less than 6,500 RPM.