Fuel injection, basic function

The current air mass/combustion is divided by 14.7 and sent to box 2. The unit is now mg fuel/combustion.

Fig 1: Illustration For Steps 1-8

Courtesy of SAAB-SCANIA OF AMERICA, INC.

In the case of a cold engine, shortly after starting, rapid load changes, knocking or a high load, the current value is multiplied by a compensation factor.

The closed loop control system value is also used as a multiplier. The value is sent to box 4.

Multiply by the value for purging adaptation. The value is sent to box 5.

The multiplicative adaptation value is also used as a multiplier and the new value sent to box 6.

The additive adaptation value is added. If the engine is running the new value is sent via box 7 to box 8.

If the engine still has not started the starting fuel is selected. The value is sent to box 8 via box 7.

Fuel mass/combustion is the fuel mass that is to be supplied to the engine. The value is sent to box 9.

Fig 2: Illustration For Steps 8-13

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Converts the value into the time the injector must be open and the new value is sent to box 10.

Before the camshaft position has been detected, injection takes place twice/combustion. Injection duration is then divided by two. Current value is sent to box 11.

Add the injector duration delay, which is voltage dependent. The value is sent to box 12.

If fuel shut-off is not active, the value will be sent to box 13.

At a specific crankshaft angle, the microprocessor controls the transistor for the injector that is next in the firing order.