Ignition Timing: Adjustments

This system utilizes the IC signal from the PCM to control spark timing. To properly control ignition timing, The PCM also relies on the following information.
^ Engine load (manifold pressure or vacuum).
^ Engine coolant temperature.
^ Intake air temperature.
^ Crankshaft position.
^ Engine speed (RPM).
^ Spark knock indication.




The Electronic Ignition (EI) system consists of ignition coil assembly, (which also contains the compression sense inductive pickup) Electronic Ignition (EI) module, Crankshaft Position (CKP) sensor, knock sensor, related connecting wires and the Ignition Control (IC) portion of the PCM make up the remainder of the system.

A distributorless ignition system, such as this one, uses a waste spark method of spark distribution.

Each cylinder is paired with the cylinder that is opposite it (#1-#4 or #2-#3). The spark occurs simultaneously in the cylinder coming up on the compression stroke and in the cylinder coming up on the exhaust stroke.

The cylinder on the exhaust stroke requires very little of the available energy to fire the spark plug. The remaining energy will be used as required by the cylinder on the compression stroke. The same process is repeated when the cylinders reverse roles.

It is possible in a no load condition for one plug to fire even through the spark plug lead from the same coil is disconnected from the other spark plug. The disconnected spark plug lead acts as one plate of a capacitor, with the engine using the other plate. These two capacitor plates are charged as a current surge (spark) jumps across the gap of the connected spark plug. The plates are then discharged as the secondary energy is dissipated in an oscillating current across the gap of the spark plug still connected. Because of the direction of current flow in primary winding and thus, in the secondary winding, one plug fires from the center electrode to the side electrode while the other fires from side electrode to center electrode.

This system utilizes the IC signal from the PCM to control spark timing. To properly control ignition timing, The PCM also relies on the following information.
^ Engine load (manifold pressure or vacuum).
^ Engine coolant temperature.
^ Intake air temperature.
^ Crankshaft position.
^ Engine speed (RPM).
^ Spark knock indication.