This Quicktime engine animation is a realistic simulation of the spark plug ignition sequence. Notice that the "Leading" (lower) plugs fire simultaneously, while the "Trailing" (top) plugs fire independently of each other. The extra spark of the leading plug late in the exhaust stroke is called a "waste spark". Using a waste spark simplifies the ignition system as only one coil and ignition signal are required for both leading plugs. The trailing plugs cannot utilize a waste spark because the timing would ignite the incoming air/fuel mixture in the next chamber.
This high-quality Quicktime engine animation is a closeup look at the spark plug ignition events.
