Ignition System Operation: Notes

This ignition system does not use a conventional distributor and coil. It uses a crankshaft position sensor input to powertrain control module (PCM/engine control module (ECM). The PCM/ECM then determines Electronic Spark Timing (EST) and triggers direct ignition system ignition coil.

This type of distribututorless igniting system uses a "waste spark" method of spark distribution. Each cylinder is paired with cylinder that is opposite it (1-4 or 2-3). The spark occurs simultaneously in cylinder coming up on compression stroke and in cylinder coming up on exhaust stroke. The cylinder on exhaust stroke requires very little of available energy to fire spark plug. The remaining energy is available to spark plug in cylinder on compression stroke.

These systems use EST signal from PCM/ECM to control electronic spark timing. The PCM/ECM uses following information:

• Engine load (manifold pressure or vacuum).
• Atmospheric (barometric) pressure.
• Engine temperature.
• Intake air temperature.
• Crankshaft position.
• Engine speed (rpm).