In a message dated 8/19/98 9:35:32 PM !!!First Boot!!!,
rareisse@postoffice.worldnet.att.net writes:
> "As soon as the switch opens, current ceases to flow from the battery
> through the coil. The collapse of the magnetic field is practically
> instataneous. As this field collapses, a voltage is "generated" which
> tries to keep the current going. This voltage can approach several hundred
> volts in the coil primary. It is the job of the condenser (or capacitor,
> ed.) to absorb this surge of voltage across the points. At the same time
> this voltage surge occurs in the primary, a surge is induced into the
> secondary (which contains many more turns of wire). The net effect is to
> "step up" the primary voltage to a level sufficient to fire the spark
> plugs. This requires many thousands of voltage depending among other
> things on compression, air/fuel ration and spark plug gap."
>
It sounds like the capacitor is protecting the points against excessive
arcing. If you didn't suppress this arc it would rob energy needed by the
secondary for the spark you really want. Has anyone ever seen an energy rating
for an ignition coil? This would be the energy stored in the magnetic field
just before the points open. It would be stated in joules. I think this rating
would be the real indicator of how "hot" the coil really is. The voltage
rating must be just the breakdown voltage of the coil. The voltage the coil
actually outputs is whatever is required to dissipate the stored energy (up to
the breakdown voltage of the coil). Does that Sports coil really need a larger
plug gap to get a hotter spark?
Bob Donahue (Still stuck in the '50s)
EMAIL - BOBMGT@AOL.COM
52 MGTD - under DIY restoration NEMGTR #11470
71 MGB - AMGBA #96-12029, NAMGBR #7-33
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