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Subaru ignition coils wire size

Practical Motorsport Wiring - Club Level

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I'm currently building a Subaru STi MY02 engine harness and would like to know if 1 square mm wire (around 17 awg) is ok for the ignition coils (coil on plug) power and power ground. We often need to use 3.5 to 3.9 ms dwell time when runnig high boost.

Jorge Morais

Following =)

I use 20AWG for the coil power and ground wiring on the EJ207 COP units and 22AWG for the signal. They draw around 6A as a peak current, but only for a short period of time.

Thank you Stephen!

Regarding power and ground, do you use the same wire size for the main and split lenghts of wire?

Jorge Morais

The Coil grounds go back to the head, and the primary feed for the coils is also shared with the injectors (Saturated) so I have an 18AWG from the PDM to the engine, and then I split it from there to the fuel rails and coils. The PDM shows an average of 2A draw with the engine under load, with occasional peaks of 3A, this would have the current draw sitting around 2.5A continuous.

Thank you very much Stephen!

I have now all the information I need.


Jorge Morais

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