Complex sentence: The wasted spark system is commonly used in the ignition systems of a four-stroke cycle internal combustion engine where the spark plugs fire in pairs, on both the exhaust and compression strokes.
Split into simpler sentences: The wasted spark system is an ignition system used with some four-stroke cycle internal combustion engines. In a wasted spark system, the spark plugs fire in pairs on both the exhaust strokes and the compression strokes.