The ECM controls the duty ratio of the linear type suction control valve (SCV), the length of time that the current is applied to the SCV in order to control the quantity of fuel that is supplied to the high-pressure plungers. Since only the quantity of fuel that is required for achieving the target rail pressure is drawn in, the drive load of the supply pumps is decreased.

When current flows to the SCV, variable electromotive force is created in accordance with the duty ratio, moving the armature to the left side. The armature moves the cylinder to the left side, changing the opening of the fuel passage and thus regulating the fuel quantity. With the SCV OFF, the return spring contracts, completely opening the fuel passage and supplying fuel to the plungers, full quantity intake and full quantity discharge. When the SCV is ON, the force of the return spring moves the cylinder to the right, closing the fuel passage, normally opened.

By turning the SCV ON/OFF, fuel is supplied in an amount corresponding to the actuation duty ratio and fuel is discharged by the plungers.

This control determines the fuel injection quantity by adding coolant temperature, fuel temperature, intake air temperature, and boost pressure corrections to the basic injection quantity is calculated by the engine control module (ECM), based on the engine operating conditions and driving conditions.

Normal Running Control

During normal running, optimum fuel injection quantity is controlled according to the engine speed and accelerator pedal pressing amount. Combined with high pressure injection of atomized fuel, this control improves exhaust gas and ensures proper fuel consumption. Compared with conventional mechanical governors, an electronic control system provides higher degree of freedom of fuel injection quantity control, thereby presenting high accelerator response, acceleration feeling and pressing feeling.

Maximum Fuel Injection Quantity Control

The maximum injection quantity is calculated by adding the mass air flow correction, intake air temperature correction, barometric pressure correction and cold operation maximum injection quantity correction to the basic maximum injection quantity that is determined by the engine speed.

Starting Injection Quantity Control

At the engine starting, after the key switch is turned to the START position to start the engine, up to return of key switch to the ON position, optimum fuel injection quantity is controlled based on the information on the starter switch, engine speed, and coolant temperature. At low temperature, the fuel injection quantity increases. When the engine started completely, this boosted quantity mode at the starting is cancelled and normal running mode is restored.

Idle Speed Variation Stabilize Control

The injection timing suitable for the vehicle conditions is controlled based on the inputs from respective sensors. The injection timing is determined by comparing actual measured values of pulse signals from the crankshaft position (CKP) sensor and camshaft position (CMP) sensor with the target injection timing stored in the map of the engine control module (ECM) in advance.

Coolant Temperature Compensation

The engine control module will advance the fuel injection timing with a decrease in engine coolant temperature. This is performed to reduce white smoke emission.

High Altitude Compensation

The engine control module with advance the fuel injection timing with an increase in altitude due to the lower air density. This is performed to reduce white smoke emission.

Cold Start Compensation

The engine control module will advance the fuel injection timing with a decrease in intake air temperature. This is performed to reduce white smoke emission.