3000GT / Stealth / GTO Forum

Originally Posted by fastbikes76

SO I did this write up a while ago on GTOOC and saw it found its way onto 3sdie, so I may as well add it here for you guys who havent seen it. This is an alternate approach to the expensive DLI's and a far more robust one too. So far mine has been hotwired for 2 years now and run 24psi on stock coils, lead and copper plugs with stock gaps.

The approach to this is the same as with the fuel pump hotwire. Stock wiring to the coil results in a reasonably strong voltage drop between battery voltage and the voltage the coil packs. I was suffering hugely with miss-fires at high boost, Keithmac advised me on how to do this so all props to him.

firstly you need to test the voltage at your coils too see if you in fact need to do this. Test as per below...

Here is how you can test things. Check battery voltage at idle directly on the battery. Then take the + lead of your tester and touch it on the inner most post of the front coil pack as you look at the engine from the front of the car while leaving the negative on the battery. Its the gold'ish looking nut closest to the coil pack bracket. If you are not getting the same voltage as the battery then this will help reduce miss-fires at higher boost levels.

With 14.4V at the battery and only 12.7V at the coils :o . Not that on its own is not too bad, however when logging battery voltage i found on hard WOT runs my battery voltage would drop down to 13.1V which in turn worked out late 11's at the coils around 6000rpm

You will need:

Standard 5 pin relay
5 Pin relay connector
30 amp fuse and Fuse Holder
Butt connectors/Heatshrink/Spade Ring
Wiring-I think I used 10 or 12 gauge

Time Involved: Should take you about 50 mins to an hour...

So here is a coil pack off the car, the wire you need to intercept is the red one. Its located on the connector for the coilpack on the right side of the coilpack on the bottom. The corresponding wire on the harness side changes to black with a white trace, it is easier to cut the black & white on the harness side than the short red bit on the coil pack side. So we will cut the black & white wire...and run Pin 87 from the relay to the COIL side and Pin 86 is the HARNESS side of the coilpack.

So what I did was remove the three 10mm bolts holding fuse box in and separate the base. I ran positive wire from the relay with the 30amp fuse holder to the big yellow 60A fuse on the left. Undo the bolt and fit ring connector underneath.(The red wire with the spade fitting is going to the relay)

Ground you can simply stick underneath the fuse box mounting bolt.

I ran all the wires up through a small hole I drilled in the fuse box base and up through a blank relay space.

But instead of using the spade connectors I recommend using the 5 pin relay connector..makes the install cleaner and simpler

Leaving you with this once the lid is back on.

Wiring in the relay is super easy and goes as follows.

Pin 30 is the 12V +
Pin 85 is GROUND
Pin 87 is to the COIL side of the black & white wire you cut (red wire on coil pack plug)
Pin 86 is the HARNESS side of the Black & white wire you cut (red wire on coil pack plug)

Finally, the fuse holder that you got...wire that in between the relay and the +12V source...I used a 30a fuse.

And that's pretty much it...double check all connections...make sure all your connections are heatshrinked and solid otherwise you will run into problems with no spark...now you should be able to run more boost and not worry about spark blow out...!

Cheers
Elton