Janicholson on mag conversion

You had some advice on an E4A conversion question yesterday & it has moved way on down in the threads by now & I posted to it also, with hope that you might have comments on mine & perhaps answers too.
If you don't mind please take a look. For whatever reason it didn't show up in the Classic view.
Thank you.



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PostPosted: Sat Jan 17, 2009 11:58 pm Post subject: Re: magneto to coil conversion Reply to specific post Reply with quote Edit/Delete this post
Jim, that E4A would probably be a bear to convert, not only due to HV path that you address, but since the primary & secondary coils rotate & it appears to me that both sides of the points are isolated from ground and rotate, it isn't going to be easy to connect to the points!
In looking into this (I have one on the bench), I noticed something else interesting that I thought I might get you to comment on. Every other spark is of opposite polarity from the previous spark.
Every few months, it seems that there is a controversy about the advantage/disadvantage of a positive vs negative spark polarity & often compounded by some who mistakenly think spark polarity is tied to POS/NEG battery ground.
Well, with the E4A mag you have both! I have never put much in the +/- argument, beyond better electron emission from a hotter electrode & that would occur not at start up when you need it most, but after a run period.
Apparently IH didn't either since theE4A alternates, every other firing.

The shaft has insulators on the bearings to isolate it from the case, which brings up another question for you.........did this mag installation utilize an insulated coupler to the mating shaft? If not, it would seem that isolation would be lost..........it must have used a phenolic insulated coupler.??

Whew, That mag is decidedly bizarre inside. My thoughts were just to get an operational spark, but I guess not on that unit. As to the polarity of spark. I agree the only small advantage to a center to ground spark is the thermionic effect of a hotter point of origin.
The plasma between the electrodes just needs to start a good fire.
Several years ago an extreme test was made with consumable electrode high current Capacitive discharge. (I have no idea where it was published) This experiment used currents of 20 to 100 times those found in normal spark ignitions.
It actually produced a flash of superheated gas into the chamber (test cylinder) that produced a significant improvement in combustion rate and flame travel due to a larger flash origin for ignition. The peak mean effective pressure was greater, and power was incrementally increased.
It was determined that the cost of consumable electrodes, and the complexity coupled with metal being "eroded" off of the tips, was not a viable solution. CDI and other hot spark electronic igniters and coils pumping into wider spark gaps (some at .080") are a reflection of the value of the idea. Exotic metals and heat control are also in the same realm of applied science. Fun discussion. His rebuilt mag looks great. I hope it performs. JimN

(quoted from post at 21:47:32 01/18/09) Whew, That mag is decidedly bizarre inside. My thoughts were just to get an operational spark, but I guess not on that unit. As to the polarity of spark. I agree the only small advantage to a center to ground spark is the thermionic effect of a hotter point of origin.
The plasma between the electrodes just needs to start a good fire.
Several years ago an extreme test was made with consumable electrode high current Capacitive discharge. (I have no idea where it was published) This experiment used currents of 20 to 100 times those found in normal spark ignitions.
It actually produced a flash of superheated gas into the chamber (test cylinder) that produced a significant improvement in combustion rate and flame travel due to a larger flash origin for ignition. The peak mean effective pressure was greater, and power was incrementally increased.
It was determined that the cost of consumable electrodes, and the complexity coupled with metal being "eroded" off of the tips, was not a viable solution. CDI and other hot spark electronic igniters and coils pumping into wider spark gaps (some at .080") are a reflection of the value of the idea. Exotic metals and heat control are also in the same realm of applied science. Fun discussion. His rebuilt mag looks great. I hope it performs. JimN

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Appreciate your thoughts,
thanks.
JMOR

Yeah, the polarity changes each time it fires. I have not seen for myself but the old guys have told me the ground-to-center pair would wear out first and you could sometimes get along for a while by swapping the pairs.