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R8 Coil wiring


lostsoul

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Pin 4 is on the left, pin 1 on the right.  

Pin 4 is the main power ground so needs to be decent sized wire.  Pin 2 is secondary ground so can be smaller.  Ground both to cyl head.

Pin 3 is the ign signal from ECU.

Pin 1 is +12V, again needs to be decent wire.  

Dont give these too much dwell, they pull about 16A at 2.5ms, I usually stick around 1.8ms which is about 8A.

 

6J4WJp1.png

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  • 2 months later...
5 hours ago, 928sg said:

Adam, Can you add recommendations on the wire gauge?

For the main power/ground I have used 18AWG tefzel, but as I said above Im only running them at 8A peak.  If you are a high boost turbo you may want to go to 16AWG.

If using Tefzel wire, 18AWG is good for about 9A, 16AWG about 12A.  Low temp PVC insulated wire would need to be bigger.

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  • 3 months later...

I know this is dragging up a old thread but since i'm asking the same question I didn't see the point in starting a new one.  These cable sizes, are these the main run for say 14v and ground or is 18wg recommended for the individual branches going to individual coils?  I've bought a link "Loom A" 5m to make a new engine harness as i'm sick of my 25year old one causing me problems.  I was going to use the red/white 8V wire as the power feed to the indiviual coils and crimp these to a larger feed wire about 6-8 inches away.

I did a quick check on a wesite and it said it should be ok but now I'm doubting myself:

https://www.dropbox.com/s/bp2qc00q2gihyx9/Screenshot 2021-02-20 at 06.57.20.png?dl=0

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0.5mm2 AVSS would be a bit borderline for powering those coils.  Probably would get away with it but I usually err on the more cautious side with PVC insulated wire.  As I mentioned above I would tend towards 18AWG or 0.75mm2 for the power supply on these coils. The main wire feeding them before it branches out doesnt need to be much bigger since only one coil at a time will be pulling peak current and duty cycle/average current is much less. 

Generally, besides voltage drop to consider, the main limiting factor in the current a wire can carry is the melting point of the insulation (copper doesnt melt until >1100°C, but some PVC melts @ ~80°C, so obviously the insulation is going to disappear long before the conductor has a problem).  Unfortunately that web page you are using looks like it doesnt consider ambient temperature, self heating or insulation properties at all.  

The Link AVSS wire is rated for continious use at 80°C and intermittent use at 120°C, when you consider your coil wiring is sitting right on top of the cyl head, it is probably sitting at about 80°C already before you even add any current effects to it...

Below is the permissible current spec from the Japanese standard that AVSS is designed to meet.  Notice how quickly the current drops away with increasing ambient temp:

Wfu3QdQ.png

 

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  • 8 months later...
On 7/2/2019 at 12:08 PM, Adamw said:

Pin 4 is on the left, pin 1 on the right.  

Pin 4 is the main power ground so needs to be decent sized wire.  Pin 2 is secondary ground so can be smaller.  Ground both to cyl head.

Pin 3 is the ign signal from ECU.

Pin 1 is +12V, again needs to be decent wire.  

Dont give these too much dwell, they pull about 16A at 2.5ms, I usually stick around 1.8ms which is about 8A.

 

6J4WJp1.png

I want to connect bmw e30 m42 engine r8 coil, do you have a wiring diagram about it, can you help me?

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  • 4 weeks later...

The 3 pin coils are dumb coils.  I dont know the platform well but I suspect these will likely have an ignitor somewhere to drive the dumb coils.  To change to smart coils you would need to remove the ignitor and run wires direct from ecu to coils.  However dwell times will likely also be wrong unless you can reprogram the stock ecu.  

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