Distributor: Description and Operation

Distributor Assembly:

The Optical Distributor sends engine speed and crankshaft position signals to the PCM. The signals are used to control ignition timing, fuel injection, and idle speed. The timing device located in the distributor is a thin disk, driven at half engine speed from the forward (left) bank camshaft. The disk has 2 sets of slots in it. The outer, "high data rate", set of slots occurs every 2 degrees of crankshaft rotation. It is used for ignition timing at speeds up to 1200 RPM to increase timing accuracy. During cranking and idle, engine speed changes with the firing pulses of each cylinder. The "high data rate" signal is used to trigger the ignition at the correct crankshaft position regardless of these changes. The inner, "low data rate", set contains 6 slots, which are correlated to crankshaft top-dead-center for each cylinder. This set is used to trigger the fuel injection system, and at speeds above 1200 rpm, where speed changes due to individual firing pulses are small, this set of slots is also used for ignition timing.