Ignition advance management

IGNITION ADVANCE MANAGEMENT

α: crankshaft flywheel signal
Δ α: fixed ignition advance (10° engine)
ON : activated coil conduction
OFF: de-activated coil conduction

Starting

During starting it is not possible to carry out the normal management of the advance because the considerable fluctuations in the rotation speed do not allow the correct calculation of the dwell and the advance.

The advance is therefore managed by taking the following as a reference:

• - for the start of conduction, the tooth at 65°;
• - for the ignition advance, the tooth at 10°.

As a result there is a fixed advance at 10° for the entire time the engine is driven by the starter motor.

Operation when cold

During operation when cold an additional correction of the advance is implemented: the increase in the advance in relation to the one in the memory is inversely proportional to the temperature of the engine.

Operation during cut-off

The ignition advance is increased at the entry into cut-off: from the moment the supply of fuel is re-enabled the advance is gradually restored to the "base" value.

Δ α: correction of ignition advance during idling
+Δ RPM: the idle speed exceeds the nominal value
-Δ RPM: the idle speed is lower than the nominal value

Operation with engine idling

When the engine is idling, the management of the advance is implemented independently of the "basic" advance.

The value of the advance during idling, which varies according to the temperature of the coolant (10° with the engine warm) is corrected in accordance with the variation of the speed in relation to the pre-set speed, which also depends on the temperature.

In particular, the advance is increased if the speed decreases and is reduced if the speed increases, in order to ensure the stability of the actual speed.