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2G Coil Hotwire

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Tanro

10+ Year Contributor
2,458
90
Jul 22, 2009
Montgomery, Alabama
Has anyone ever done a coil hotwire/rewire like we do with our fuel pumps? I am suffering from a severe voltage drop to my coil pack causing missing at low rpm, especially when getting into boost. I've grounded the shit out of everything. I have 1 4ga 12" ground from the battery to the firewall. 1 4ga 27" inch ground to the starter bolt to the battery. The oem ground strap on the intake manifold. and 4 extra 8ga grounds. One on the coil pack bracket to firewall. One on the intake manifold to firewall. One on the thermostat housing to firewall. and One on the head to the battery.

Probably taking them all off except the coilpack ground as that is the only one that helped much. But I am still getting a voltage drop of 2-6 volts to the coil vs battery voltage.

Was thinking running a rewire with 10ga primary wire and a 5 pin relay would help.
 
The coil isn't dropping voltage. The wiring to the coil is dropping voltage. Or the alternator is a piece of shit.

But its not the coils. Or if it is has been about 14 bad coils. 4 sets of which were/are new. I've tried rock auto coils, sent those back. Parts store coils, sent those back, ebay coils, sent those back without installing them because they ohmed out bad. And pile of dsm/3000gt coils I had in the shop. Currently using OEM coils that ohm out in spec and have about 4200 miles on them and still haven't been able to solve this problem. Which has lead me to believe that its either a voltage problem. Or a fuel problem. But the fuel pump is rewired, and IDCs are lower than 80% and the AFRs are what they should be. So I don't think its fuel unless my wideband is bad, or its bad gas. And i've tried several brands of gas. None seem to have an effect. Heat soak is really the onlything that changes it. That and battery voltage.

The wiring to the coils is not showing the same voltage as battery voltage. There is a voltage drop before the coil. Bettery wiring could help. I just don't fully understand how the coils are switched so I'd be guessing about how to wire up a relay to control a bigger wire with less resistance.
 
You should have a severe voltage drop inside the coil. If you don't have one, that means you have other problems. The coils create that voltage drop as current builds a magnetic field in them.

Tanro is asking about a voltage drop on the 12V feed to the coils. You should minimize that, which is what he is asking about. The 3000GT guys did it, and saw some differences. Their coils are basically the same as ours.

You can do it. And you should be able to do it without cutting any wires. I think you can just unbolt a ring terminal at the coil +, and add the output from the relay to that. If you are seeing a 2V drop, it is a worthwhile upgrade as it will improve coil energy by 20% or more. If you are seeing a 6V drop, it absolutely should be done.
 
Brads understands what I am on about.

The available voltage going to the coil is not what it should be. No where near it. If say battery voltage reads 13.1 v. I am getting 10.1-11.4 volts at the coil primary wires (remember secondary wires are HT leads/plug wires). I am not measuring the voltage to the secondary wires. The secondary wires and coils are both ohming out to what they should do.
 
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