Barney,
Great info, after reading your response I think we all should run the hotter
coils!
Safety Fast!
Ross Overcash
Ayer, MA USA
NAMGBR 2-1172
74B decrepit but running!
http://home.earthlink.net/~jroverca/
> -----Original Message-----
> From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net]On
> Behalf Of Barney Gaylord
> Sent: Monday, July 24, 2000 2:11 PM
> To: Geoffrey Gallaway
> Cc: mgs@autox.team.net
> Subject: Re: Ignition Coils
>
>
> At 09:36 AM 7/24/2000 -0400, Geoffrey Gallaway wrote:
>
> >I just bought a stock ignition coil from propermg for 19.95 although I
> could have bought the Lucas sports coil at 40,000 volts for a few dollars
> more. ....
> >
> >So, what voltage is the standard coil, 20,000 volts? How much does the
> sports coil actually gain? ....
>
> 17,000 to 20,000 comes to mind as standard, although I think a
> stock engine
> may actually run (marginally) with as little as 7,000 volts.
>
> The voltage required to make a spark jump the gap at the plug is
> determined
> by the size of the gap and by the pressure of the air in the cylinder.
> Bigger gap = higher voltage required. Higher compression = higher voltage
> required. Once the voltage in the coil builds up to the required
> level the
> spark jumps the gap and the voltage goes away. The voltage will never go
> any higher than what is required to make the spark jump the gap,
> regardless
> of what coil you have. On the flip side, if the gap is too large, and you
> don't have enough voltage available, then you will never get a spark. The
> highest voltage requirement occurs at the point of highest
> dynamic pressure
> in the cylinder, which for most engines is around 2500 rpm and full
> throttle, which is the same condition where you might experience spark
> knock with high compression and cheap gas.
>
> HOWEVER, when you have a coil that is capable of putting up a higher
> voltage, then you can open up the gap at the spark plug, which in turn
> demands a higher voltage to affect the spark, which in turn will
> give you a
> higher voltage (and probably longer duration) spark. A hotter coil may in
> fact be necessary in a high compression race engine just to make the spark
> jump a standard size gap. With normal compression ratio and a 40KV coil
> you can open the spark gap from .025" to .035" or more and still get a
> reliable spark. The hotter spark will then make it easier starting and
> have much less probability of misfire under various running conditions.
> You would also be less likely to ever have fouled spark plugs. Also the
> system would be more tollerant of maintaince neglect, as it could fire a
> spark across a badly worn plug with a much larger gap.
>
> I happen to like my 40KV coil and .035" spark plug gap setting, finding
> easier starting, more consistent smooth idle, and never a misfire with the
> hammer down. I think it's a keeper.
>
> Barney Gaylord
> 1958 MGA with an attitude
> http://www.ntsource.com/~barneymg
>
>
>
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