Wasted spark

Wasted spark ignition system in a four-stroke cycle internal combustion engine refers to engine which fires both on the exhaust and compression strokes.

Design aspect

This design is simpler than a conventional ignition system, but the extra sparks reduce the lifespan of components such as contact breaker, and spark plugs.

Advantages

This design allows smaller number of more powerfull coils to replace a larger number of smaller coils in the same limited space.

Where used

Examples of engines using this design include the Harley Davidson V-Twin, Citroën 2CV, Mazda B engine and Chrysler V10. Some Ford engines also do.

Many Honda Motorcycle engines also follow this design to take the advantages of this system. That is, it uses a smaller number of more powerfull coils to replace a larger number of smaller coils in the same limited space.