Run Mode

Once the engine starts and is operating normally, timing is controlled by the computer, based upon information received from the data sensors. Total spark advance is determined by 3 factors: coolant temperature, engine speed and manifold vacuum.

In a cold or warm engine, as indicated by coolant temperature sensor, RPM has no affect on advance. Under these conditions, the advance curve is determined by vacuum signal only. In a hot engine, computer is programmed to consider engine speed in addition to manifold vacuum, to determine total spark advance.