Can I do wasted spark?

Some ECUs can schedule the spark events in a wasted-spark mode, where one coil drive output is used to cause sparks for two cylinders. In this mode, the ECU causes two spark events per engine cycle, where one spark achieves firing while the other is a benign 'wasted' spark on the exhaust stroke in the paired cylinder. The pairing of cylinders sharing one spark coil is currently inferred from the firing angles of all cylinders, assuming that those furthest apart in firing angle are paired.


Additionally, 360 degree mode 'wasted spark' is also supported (regardless of whether shared coils are in use). This means that sparks begin on a 360 degree pattern before full cam/crank synchronisation is attained. On average half the sparks will be 'wasted' in the exhaust stroke but the other half will initiate firing. Overall this improves engine start by causing firing before the engine has turned over enough times to confirm full synchronisation. This is optional as it is not suitable for certain engine configurations.

All ECUs with the MPC5xxx processor family, such as the M670, support wasted spark.

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