Ignition, basic function

When the idle speed control is active, the ignition timing is adjusted to stabilize idling speed. The value is sent to box 3.

When the idle speed control is not active, the ignition timing is obtained from a load- and speed-dependent matrix. The matrix value is optimized for the lowest fuel consumption (best torque). The value is sent to box 3.

One of the ignition timing calculations is selected, depending on which function is active. The value is sent to box 6.

The timing is corrected according to the coolant temperature and intake air temperature. The value is sent to box 6.

If knocking occurs, the amount by which the ignition should be retarded is calculated. The value is sent to box 6.

The compensation angle and knock retardation are totalled to give the current ignition timing. The value is sent to box 7.

Starting ignition is selected when the engine has not yet started. The value is sent to box 9.

The ignition timing at start is calculated based on the intake air temperature and coolant temperature. If the engine is running the value is sent via box 7 to box 9.

At the calculated crankshaft angle, the microprocessor controls the transistor for the trigger that is next in the firing order.