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Old 07-31-2019, 09:32 AM
Dave9111 Dave9111 is offline
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Quote:
Originally Posted by joe_db View Post
I will emphasize again the heat produced by a 4 ohm coil is EXACTLY THE SAME regardless of the resistance of the primary winding vs. any internal ballast.
Ohm's law applies
I agree. It really doesn't matter how the resistance is created, however using resistive wire would probably better spread the heat throughout the coil vs using a discrete carbon or ceramic resistor.

My point before was that the heat is best kept OUT of the coil entirely.




Note 3: The Moyer coil and other 4 ohm coils have been well proven to last on A4s. Empirical data is good here
Note 4: I think a 4 ohm coil produces higher voltage than a 1.4 ohm coil ballasted to 4 ohms.[/QUOTE]

That is really great that you were able to attach pictures of a scope trace!

As you can see this is nothing close to DC! DC would be flat lines that shift up and down as the points go open and closed. The inductance of the primary and secondary limit the current flow and create the "ringing" that you see in the scope trace.
Coil voltage output is determined by the turns ratio of the coil. You only need enough voltage to jump the spark gaps in the distributor and the plug. The other important part is the amount of energy that is released from the coil. However the Atomic 4 is no high performance, high rpm race engine, so its needs are pretty basic. Its more like a 1930's-50's tractor engine.
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