With the original roadster distributor, the ignition trigger is supplied by the breaker points as the contacts open and close. With the EI distributor, the trigger is instead, provided by the reluctor (on the distributor rotor shaft) and the pick-up coil (inside the distributor). As the reluctor rotates, the amount of magnetic flux passing through the pick-up coil changes. The changing magnetic flux generates an electrical signal in the pick-up coil. This is commonly referred to as the Hall effect. This electrical signal is conducted into the IC ignition module (mounted on the side of the distributor), which triggers the primary current running through the ignition coil. This generates high voltage in the secondary winding of the coil, which is conducted to the spark plugs.
The IC ignition module (attached to the side of the distributor housing) performs multiple functions with 5 individual circuits:
1. Spark timing signal monitoring circuit This circuit detects the ignition signal sent from the distributor pick-up coil, and amplifies the signal.
2. Lock-preventing circuit This circuit cuts off the ignition coil primary current when the ignition switch is ON and the engine is stationary. If the ignition coil primary current is allowed to flow under such conditions, excessive current will be drawn because of low internal resistance of the ignition coil. This would result in an abnormal temperature rise in the ignition coil or discharged battery. These malfunctions will be prevented by this lock-preventing circuit.
3. Duty control circuit This circuit controls the ratio of the ignition coil primary current ON-OFF time periods, in one cycle of ignition operation. This is equivalent to the dwell angle of the conventional points type distributor. In order to provide high performance spark firing over a wide range of driving speeds, this duty is controlled by the source voltage and the ambient temperature, as well as by the engine rpm.
4. Power switching circuit This circuit is used to make or break directly, the primary circuit current of the ignition coil.
5. Current limiting circuit This circuit controls the current value so that excessive current will not flow through the power switching circuit.
That's about it for its theory of operation for the EI distributor.
Gary Boone '70 SRL311-13767 WyCROC member http://www.wycroc.org/