LS2 TRUCK / YUKON Coils - Discussion, Experience, Ideas, Pictures

[Shane_Sawatzki]

Standard 12V relay like this -




Wired like this -

[judasentinel]

Thank you, Shane. The pic and diagram you showed is for a 5 pin relay, I see....is there any use for the 5th pin in the middle or can that be left alone?

As per your description then, are there 2 sources of 12V power coming into the relay? As I see it, one is 12V coming from the battery and the other is another 12V coming from the 2 pin connector. And does the ignition (turning the key) turn the 12V power on, on the pin 86?

I have found 4 pin relays, with pins 30, 87, 86 and 85. From what I have read, pin 30 connects to the battery 12V, and the 87 connects to the coil, 85 is ground, and 86 is connected to the ignition. Does this sequence make sense? In your initial comment, you had said that pin 30 goes to the coil and 87 to the battery. Does it matter whether it is 30 or 87 that faces the battery?

I appreciate you clarifying this for me.

[Shane_Sawatzki]

you could theoretically swap 86 and 85 and it wouldnt matter.

as well you could swap 87 and 30 and it wouldnt matter.

when 86 sees 12v from the stock ignition harness with pin 85 grounded, it trips the relay and joins pin 87 and 30 together.

[judasentinel]

Thank you, Shane. I will get the 4 pin relay and wire it up as you suggested. Seems pretty straightforward now. I appreciate your input

[AL91GTR]

The extra pin is for a switched circuit where something else is energized when powered off. Just wire like Shane's sketch and it's good to go.

[judasentinel]

I have purchased the coils, and am awaiting their delivery.


Is my understanding correct that the relay will have two 12V inputs, one from the coil 2 pin connector (ignition switch-based), and the other one directly from the battery?

What do I tap into, in order to get 12V from the battery? In R33 GTR the battery is in the trunk. Should I just hotwire the 12V to the battery box in the engine bay?

[judasentinel]

Update:

Coils arrived and I have to test them to see how they are.

I made the harness using the info in this thread, using a 40A 4-pin relay from Crappy Tire. Now I have a few questions...

a. Is it ok to join the 6 wires from the coils together to connect to a the single 12V power source at the relay, or does one have to run all wires in parallel and then join them all together at the relay?
b. The two right most pins on each coil are grounds, one a chassis ground and the other a coil ground. Is it ok to join all 6 chassis ground wires together from the coil plugs and ground them at one single point?
c. Where should I ground the the 6 coil ground wires? I am keeping them separate from the chassis ground, so want to know what the best location is for them to be grounded

This is my current wiring setup:

1. 12V switched - all 6 are joined together and they run as a single wire to the pin 30 on the relay
2. 5V signal wires - each is individually wired to the 6 pin connector that connects on the other end to the factory harness from the ECU
3. Coil ground - all joined together, and I am looking for a point to ground them together
4. Chassis ground - all joined together and to be grounded to the head or maybe even one of the holes on the stock coil mounting bracket

I have read that one can run the stock ECU with this setup without needing to increase the dwell time from 3.5 ms to 5 ms, if one has direct 12V power coming in directly from the battery thru a relay. Is that safe or am I actually running the risk of frying something in the car?

Thank you...