Dyna coil polarity

chrispix · Aug 20, 2016

I recently purchased a 5 ohm Dyna Coil from Old Britts (http://www.oldbritts.com/51_100001.html) to put on my '75 MkIII with Boyer ignition. Unfortunately it looks different from the photos in all the wiring diagrams, and the 2 leads are completely unlabeled. Checking with Old Britts, but I thought someone here might know as I'd like to try to wire it up this weekend. Anyone know for sure which lead is which? Or is there a way to test it?

chrispix · Aug 20, 2016

Hmmm, now that I look at it, it looks like they sent me the Power Arc instead of the Dyna. https://www.oldbritts.com/51_150102.html

comnoz · Aug 20, 2016

chrispix said:
I recently purchased a 5 ohm Dyna Coil from Old Britts (http://www.oldbritts.com/51_100001.html) to put on my '75 MkIII with Boyer ignition. Unfortunately it looks different from the photos in all the wiring diagrams, and the 2 leads are completely unlabeled. Checking with Old Britts, but I thought someone here might know as I'd like to try to wire it up this weekend. Anyone know for sure which lead is which? Or is there a way to test it?

There is no polarity to a wasted spark coil. Jim

maylar · Aug 21, 2016

comnoz said:
There is no polarity to a wasted spark coil. Jim

No polarity to a dual output coil. Individual coils are polarized, wasted spark or not.

comnoz · Aug 21, 2016

maylar said:
comnoz said:

There is no polarity to a wasted spark coil. Jim

Click to expand...

No polarity to a dual output coil. Individual coils are polarized, wasted spark or not.

True, but any dual output coil on a Norton twin is going to be wasted spark, unless you have figured out how to put four plugs in a Norton cylinder head.

seattle##gs · Aug 21, 2016

so the Power Arc coil is compatible with a Boyer?

comnoz · Aug 21, 2016

seattle##gs said:
so the Power Arc coil is compatible with a Boyer?

No

pommie john · Aug 21, 2016

comnoz said:
seattle##gs said:

so the Power Arc coil is compatible with a Boyer?

Click to expand...

No

If it's 5 ohm, I would have thought it's OK?

comnoz · Aug 21, 2016

pommie john said:
comnoz said:

seattle##gs said:

so the Power Arc coil is compatible with a Boyer?

Click to expand...

No

Click to expand...

If it's 5 ohm, I would have thought it's OK?

When using electronic ignition there is more to it than the resistance.

You also have to consider the inductance and the current capability to know the correct charge time. The charge time is built into the electronic ignition module and generally can not be changed. The coil must have a charge time that is compatible with the module or one or both may be damaged. Jim

maylar · Aug 22, 2016

The 5 ohm Dyna coils have been used very successfully with a Boyer. Lots of people use them. I would hesitate to use the 3 ohm version, as I don't know the Boyer's max current spec, but I think I saw something here from Dyno Dave saying they're OK too.

It's a dual output coil, so polarity doesn't matter. One plug will be negative, the other positive, but both will spark.

comnoz · Aug 22, 2016

maylar said:
The 5 ohm Dyna coils have been used very successfully with a Boyer. Lots of people use them. I would hesitate to use the 3 ohm version, as I don't know the Boyer's max current spec, but I think I saw something here from Dyno Dave saying they're OK too.

It's a dual output coil, so polarity doesn't matter. One plug will be negative, the other positive, but both will spark.

Very true.
The Boyer does not have dwell control like some of the newer ignitions. Pretty much any coil made for a points system will work with the Boyer.
A 3 ohm coil on a Boyer will run hot -unless you use a ballast resistor. Pretty much borderline in my opinion. Jim

Dyna coil polarity

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