Computer Controlled Ignition

As engine turns distributor shaft, shutter blades of rotor/armature assembly pass through Hall Effect sending unit's pick-up coil. A signal is then sent to the ECU.

In addition to receiving engine speed information from distributor, the ECU receives engine load information from intake manifold. Speed and vacuum signals are monitored by the ECU to control spark advance and dwell.

A throttle switch provides throttle information. Under normal conditions, throttle position signal is sent to the ECU.

The manifold vacuum signal is also processed by the control unit to control ignition timing. When throttle is closed, (during deceleration and idle) the circuit is closed, and no signal is sent to the ECU.

The ECU analyzes all information, and interrupts signal to ignition coil primary circuit. This causes a high voltage surge in secondary circuit, firing spark plugs at proper time.

The knock sensor detects engine detonation. The ECU receives a signal from the knock sensor during engine detonation and then retards timing. Timing is retarded 2° every 20 milliseconds until maximum retard of 6° is obtained, or detonation stops. Timing is then advanced in 1° increments every 20 milliseconds, until base timing is achieved or detonation begins again.