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Huge mistake ignition coils

Practical Motorsport Wiring - Club Level

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Hi everyone so I built my very first harness for my 2jzgte. But I made a huge mistake and I can't belive I missed this. So I had decided to add ign1a coils but I only have one 35 amp relay wired on it and my fuse box is now full. Could anyone maybe give me some ideas or am I screwed , could I just run a larger amp relay? If so do they make a mini relay to fit in my busman box?

Thanks in advance for the help


You have a 35A relay providing switched power for the coils? Is there anything else on the same circuit? If the coils are the only current draw on that circuit then the 35A relay (and presumably similar rated fuse) is more than adequate to supply the coils.

Interesting cause everyone is telling me diffrent that I need to run two relays with these smart coils. That they should be broken up coils 1-3 on one relay and 4-6 on a second 🤷🏾‍♂️

Due to the fact that the ign1a smart coils draw so much.

Apparently they draw upto 19 Amps!

That is about 2.5 times the normal COP coil!

I would say to be safe, yes you either need a higher capacity relay with associated big wiring or two relays as recommended.

So would I be able to piggy back a proper setup off my already made relay or would that cause issues?

Just trying to get some ideas

If you can split the current relay outputs to just the three coils and then add another relay, possibly with new power wiring back to the fuse box, it could be fed by the same trigger without issues.

Perhaps create a diagram of the current configuration and your understanding of the solution?

ok yes that's exactly what i was thinking as well i could do. thank you


This is the 9ms dwell curve for a genuine IGN-1A coil, running at 14V and 5,000rpmon a MoTeC M130. The vertical marks are 2ms divisions and the horizontal rows are 4A each. So this coils is drawing approx 18A at the peak of a 9ms dwell. The power supply that is driving this supplies 5A peak and there is a 2 farad capacitor in the circuit to maintain maximum current supply. The feed into the coil has a 5A slow blow fuse for protection. This dwell time is pushing the coil to peak saturation, extending the dwell beyond this does not energise the coil further. This Dwell value would be used with the understanding that it can reduce the life of the coils. The 11ms shows how extending the dwell does not increase the current drawn.


IGN-1A 9ms Dwell by Stephen Dean, on Flickr


""  IGN-1A 11ms Dwell by Stephen Dean, on Flickr

The 5ms curve is the manufacturers recommended dwell time for these coils at this voltage, this draws only 8A at 5msand can be seen that it stops the dwell just before the coil current draw hits the knee point and increases the current draw rate.

IGN-1A 5ms Dwell by Stephen Dean, on Flickr

This is something most people don't seem to understand. Yes, these coils CAN draw a bonkers amount of current with crazy dwell times however you're A. not going to run dwell passed 5ms, and B. they're not going to be run at 100% duty cycle.

Do the math, figure out how much duty and dwell you'll be running at redline and give yourself a cushion. More than likely you're talking sub 3A continuous per coil.

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