<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> The wasted spark system is an ignition system used in some four - stroke cycle internal combustion engines . In a wasted spark system, the spark plugs fire in pairs, with one plug in a cylinder on its compression stroke and the other plug in a cylinder on its exhaust stroke . The extra spark during the exhaust stroke has no effect and is thus "wasted". This design halves the number of components necessary in a typical ignition system, while the extra spark, against much reduced dielectric resistance, barely impacts the lifespan of modern ignition components . In a typical engine, it requires only about 2--3 kV to fire the cylinder on its exhaust stroke . The remaining coil energy is available to fire the spark plug in the cylinder on its compression stroke (typically about 8 to 12 kV). </P>

Distributorless waste spark ignition systems can be triggered by a