Ignition, basic function

When idle speed control is active, the ignition timing is adjusted to stabilise 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 optimised 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.

In order to heat the catalytic converter as fast as possible after starting, the ignition will be retarded. The value is load and engine speed dependent.

The function is active when the coolant temperature is above -8°C and below +35°C.

The value from box 5 is added to the value from box 3.

The ignition timing is corrected depending on the engine 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 added to the current ignition timing. The value is sent to box 7.

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

Starting ignition timing is calculated depending on intake air temperature and engine coolant temperature. The value is sent to box 9 via box 7.

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