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Old 09-22-2011, 11:08 AM
smosher smosher is offline
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I don't know what a coil is rated for in watts, but here's the calculations
based upon a 3.3 ohm coil.

14.2 volts / 3.3 ohms = 4 amps

4 x 4 x 3.3 = 61 watts

12 vdc / 3.3 ohms = 3.6 amps

3.6 x 3.6 x 3.3 = 47 watts

61 / 47 = 130 percent

We know heat kills coils and at 14.2 volts the coil has to sink 30% more heat.

To decrease the amps in a 14.2 system to the draw in a 12 volt system you would add a ballast resistor to the coil.

14.2 / 3.6 = 4 ohms - 3.3 coil = .7 ballast.

So to me this means that if we add a ballast resistor we can reduce the heat
in the coil by 30% and still provide the 14.2 to the battery.

knock on wood, as I have an electronic ignition and I have used both a pertronix and an autozone coil, both oil filled and for 5 years I haven't had a problem. My Alt charges at 14.2 volts. The pertronix coil moyer sells is epoxy which is for vibration area's, oil coils have better cooling.

The question is what coil and where are they mounted ?

Steve
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