R8 Ignition Coil Grounding

Hello everyone, quick question on what is the best / cleanest way to ground ignition coils. With the R8 VAG coils having 2 grounds per coil and it being a 6 cylinder, there's 12 grounds total. I would just run them all together but it's a lot of wires and kind of bulky. Curious to know if anyone has done or if it is safe to splice them all into a single 16awg m22759/32 wire (matching the coil power feed) and grounding through one wire to the head. Any input is appreciated thank you!

Hey Charles,

It's perfectly fine to splice all the coil grounds into a single 16 AWG ground wire.

I'd generally follow the same wiring principle as the 12V supply side. For example, if you're running a single 16 AWG feed that branches out to individual 20 AWG supplies for each coil, you can do the same thing on the ground side.

Keep in mind that one of the grounds on the R8 coils is a power ground while the other is a signal ground, so neither typically needs a particularly large conductor. To keep things simple, I'd just run both as 20 AWG from each coil and splice them into the main ground.

The important thing is that the total current flowing through the main ground conductor is well within its capacity. Since only one coil is typically charging or firing at a time (unless you're running a batch fire setup), a single 16 AWG ground is more than capable of handling the load.

The main thing I'd focus on is keeping the ground point clean and ensuring all the coils share the same ground reference.

Yes that's exactly how I have it for the 12V supply, 16 AWG to individual 20 AWG so I will match that on the ground side. Thank you for clearing that up for me. On a side note with these coils I have always ran both grounds as power grounds to the cylinder head as suggested by Link ECU, MaxxECU, and a few others and never have ran into any issues. Would it be safe to run both grounds per coil (signal ground and power ground) on a single 20 AWG and go to the head like normal? Almost like branching a 16AWG ground to 6 20 AWG grounds (one per coil) and at the coil connector, crimp an additional 20 AWG or 22 AWG onto pin 4 (main power ground) and loop that second wire into pin 2 (secondary ground / signal ground). Hope that makes sense lol. Just trying to see what would be the cleanest way to ground them while being safe.

Piggybacking on this thread as I had a similar question.

I am building a street / clubsport harness (or rather heavily modifying the OEM harness) and the OEM harness terminates its grounds on the chassis via a dedicated grounding stud.

I am planning to use this OEM point for the ECU chassis as well, but should I also run all of my ignition grounds to this point?

From a star point methodology I believe this makes sense, but most of the information I see (and hear in the HPA courses) says to ground coils to the head / block.

I would ground coils and ecu to one point on the head to follow that star point grounding.

Caleb, just following up on my previous comment. Ive attached a picture of what I was mentioning with grounding that signal ground on the R8 coil. Just used some spare wire to show what I was asking basically. Wanted to know if it's safe to just tie that coil signal ground (pin 2) via a 20awg or 22awg wire into the coil power ground (pin 4) as a double crimp along side the 20awg power ground wire. That 20awg power ground will obviously run back to the branch point of all 6 coils and then splice all 6 20awg power grounds into a 16awg that will go to the head.

Posting to correct some of the info that has been quoted above.

There is no "signal ground" on these coils. Pin 4 is the secondary winding ground, so low current but high voltage, it only needs to be small wire but it should be connected to the cylinder head that the coil is fitted to so there is a direct path for spark return. This secondary ground is especially important when the coils are not fitted to the original VAG engine as in the oem designed application the metal "stalk" contacts the spark plug hex as the spark return , pin 4 is only there as a "backup" in the OEM scenario, but often in non-oem applications the stalk will not make electrical contact with the hex so pin 4 is the only return path. I suspect tefzel will handle the high voltage better, but I have had one customer with an aftermarket R8 coil kit where the stalk didnt make contact with the plug and the high voltage eventually "ate" a hole in the ground wire insulation causing a hard to diagnose misfire (It was probably standard PVC wire).

Pin 2 is the main power ground for the primary, and these coils can pull big current if you need high energy. The factory uses 2.5mm2 wire and MCP contacts for pin 1 & 2, I have measured about 18A peak near saturation (~3ms), and the factory runs them close to that on the TFSI models. Average current draw is much less due to the low duty cycle, so 20AWG wont catch fire and will probably work ok in some cases, but keep in mind they will not output anywhere near their designed energy output as you will get a large voltage drop at the coil when it is charging.

Thank you Adam, in that case that it is a "backup", I will just ground both to the head like normal.

Thanks Adam, appreciate the clarification.

I think I may have been mistaking the setup for something more like an LS1-style coil arrangement.

Thanks for taking the time to explain the differences with the R8 coils. Always good to learn something new.

And apologies Charles if I've caused any confusion there. I'd definitely follow Adam's advice on this one and continue grounding both circuits as intended.

No worries, thank you for the input Caleb