The Ford Barn - View Single Post

B_man_Al · 07-30-2013, 06:26 AM

BillM ...

I'm not sure of the tempco for the ballast resistor, but any coil which is wound with copper wire (all of them I believe) has a positive tempco of .293 % per degree C. Check the spec on the coil, the 1.5 ohms is probably at room temp. Pick a number for the internal coil temp after a hot run .... probably around 80C, maybe more. If so 80C-25C= 55C degrees. The increase in coil temp will then be 55 x .293=16% increase.

If the coil is 1.5 ohms at room temp (25C) then it will increase by 16% at 80C or .24 ohms. The new coil resistance will then be 1.74 ohms.

07-30-2013, 06:26 AM	#34
B_man_Al Senior Member Join Date: Feb 2011 Location: Ottawa ON Canada Posts: 301	Re: Mallory tech answer to coil/ballast ? BillM ... I'm not sure of the tempco for the ballast resistor, but any coil which is wound with copper wire (all of them I believe) has a positive tempco of .293 % per degree C. Check the spec on the coil, the 1.5 ohms is probably at room temp. Pick a number for the internal coil temp after a hot run .... probably around 80C, maybe more. If so 80C-25C= 55C degrees. The increase in coil temp will then be 55 x .293=16% increase. If the coil is 1.5 ohms at room temp (25C) then it will increase by 16% at 80C or .24 ohms. The new coil resistance will then be 1.74 ohms.