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I am trying to determine the power wire size needed for Bosch 0 986 221 024 coils for a 6cyl engine with an 8500 RPM redline in a 911. I see a reference for 10.4A below and also one for 19.2A. Any help is greatly appreciated as I plan my harness.
The data from the coils I have is as follows:
Dwell 1.7ms for 10.4A at 14v
Overdwell is 19.2A
Coils are said to fit a Porsche twin plug head perfectly
Pin-out
1 = switched Ignition Power
2 = logic ground
3 = EST signal
4 = Ignition High Current Ground
8v = 7.0ms
10v = 3.0ms
12v = 2.2ms
14v = 1.7ms
16v = 1.4ms
18v = 1.2ms
I would use 20AWG for the Power and Ground (pins 1 & 4), and you can keep with the 20AWG for the signals (pins 2 & 3) or drop down to 22AWG. The average current draw from a coil is quite low, so even though it will potentially peak at 19.2A, it will be at that peak for an absolute minimal percentage of the overall duration of the pulse.
At 6500 rpm you have around 18ms between firings, so the coil is only dwelling for ~10% of that time, giving time for the wire to dissipate and current induced heating. Halve this for Wasted Spark systems.
Thank you for the quick reply!
