Posted by Bob on July 02, 2015 at 20:45:59 from (64.255.159.192):
In Reply to: Coil Polarity posted by Steve@Advance on July 02, 2015 at 19:41:28:
IMHO, coil/spark polarity makes NO difference in the starting of a cold engine.
But once the engine is running and warms up, the center spark plug electrode is HOTTER than the ground electrode, making it a better emitter of electrons (thermionic emission).
For this to work, the center electrode must be "fired" with a negative-going pulse.
Which is exactly what happens when the coil primary polarity is "correct".
In my experience, having the coil polarity correct CAN help prevent miss-fire under lean conditions, or full-load conditions, when the throttle is wide open and compression pressures are at their max.
On the other hand, many modern engines have a "waste spark" setup that fires two sparkplugs at the same time, one with a negative-going pulse, and the other with a positive-going pulse, and those engines run just fine. (I guess 'cuz they simply have a HOT spark to begin with!)
Also, typical old tractor magnetos fire every other plug with the opposite polarity. I wonder hoe many of my fellow tractor "GURUS" realize that?
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