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wasted spark ignition

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals


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If I set a motor up to run as a wasted spark ignition does this mean I can do away with a cam sensor as the ECU doesnt need to know what stroke each cylinder is on.

ECU still needs to know the valve timing... How else would it know when exactly to fire spark plugs?

In wasted spark, the plugs fire for two cylinders at the same time. The cylinder that is compressing with closed valves, and the cylinder that is on the exhaust stroke with an open exhaust valve. One spark is "wasted" since it doesn't initiate combustion. So the plug for a given cylinder fires once every 360 degrees of crankshaft rotation. No need to know which phase the engine is in -- so one less sensor.

On 4g63 we still have crankshaft sensor and camshaft sensor although wasted spark system is employed...

Thanks for the replies. I thought I could do away with the cam sensor but if I do that then I can only run the injectors in batch fire, which apart from idle and low RPM response might be ok. But individual throttle bodies might worsen the affect. Im looking to add EFI to an old CB750 motorbike. Im just trying to sort out all the issues prior to finishing the bike.