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Ignition coil wireing amp rating

PDM Installation & Configuration

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Discussion and questions related to the course PDM Installation & Configuration

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I'm planning out the wireing diagram for my gt40 project converting a ford 302 windsor v8 to efi with sequential ignition using a PDM for the power supply I'm currently planning on using either ls1 or ign-1a ignition coils looking up the max current online says they can draw up to 10-15A each coil I am assuming that as they aren't all charging / fireing at the same time the power supply doesn't to be sized for the combined current but can't find any info to confirm

From my understanding, that would be correct. The amp draw will be affected by the dwell time though.

There is a max duty cycle on IGN-1A type coils of 40%, so it's load requirement is already 40% of 15A (6A each). If you figure your maximum RPM (divide by two since it's a 4-stroke), and coil dwell time, you can determine the duty cycle you will require. That is what you use to select the proper wiring size. I think you'll find that 18 or 20 awg will be fine, which is why that's what you see in factory harnesses.

David can I ask why you half the RPM? Is this for wasted spark? Surely if sequential the coil will ignite once every 4 revolutions?

Not for wasted spark. A four stroke engine, turns two revolutions for each cycle, there is one spark per cycle. So you need to divide RPM / 2 to get the number of sparks per minute per cylinder.

Sorry David, had brain malfunction and clearly need sleep.

There are two things to consider, the heating of the wiring, in which case the average current draw would be a good guide and the actual resistance that will affect the voltage and current to the coils, and I'd suggest up-sizing to improve the coils' outputs. There really isn't a down side other than a very small additional cost to the budget and vehicle mass.

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