Ignition System: Description and Operation

Fig. 15 Ignition System Component Layout:

The controls in this ignition system are completely electronic. The distributor has no centrifugal or vacuum advance mechanisms. The Hall sender inside the distributor sends a signal to the control unit at 60° BTDC for each cylinder. From these signals the control unit determines the engine speed and crankshaft position.
By using an electronic ignition control system with a knock sensor, the ignition timing can be optimized for all operating conditions. The engine can now operate closer to the knock threshold where it will operate more efficiently and with higher power output. Another benefit to this type of ignition system is a reduced sensitivity to differences in fuel octane. The ignition system will automatically adapt to regular or premium unleaded fuels.
A map of ignition timing points is programmed into the ignition control unit. The control unit determines the optimum ignition timing based on inputs it receives from various sensors. Knock regulation is done individually for each cylinder. If a cylinder begins to develop ignition knock (detonation or "pinging"), the control unit will retard the ignition timing for that individual cylinder to eliminate the knocking. When the knocking has stopped, ignition timing is returned back to its optimal setting.
The control unit (located in the center console, under the radio), receives the following inputs:
Engine speed and crankshaft position (from the ignition distributor)
Engine load (from the manifold pressure sensor in the control unit)
Ignition quality (from the knock sensor)
Throttle position
The control unit then determines the optimum ignition timing and operates the Hall ignition control unit which activates the ignition coil.