At 07:03 PM 7/26/2000 -0600, Larry Hoy wrote:
>....
>Seems that what you are saying is the higher output coils are a waste of
money unless you increase the gap of the plug.
>
>What is the procedure for determining the maximum spark plug gap for any
given coil?
Trial and error? You can sometimes make it pretty big, but watch out. If
the gap is too big it won't fire (consistently) under full throttle
conditions. If the gap is at the upper end of its limit, any minor
abberation, like a little plug wear or a change of fuel, will put it over
the edge and cause misfire.
Ideally you would like the largest gap possible where the voltage
requirement will not (EVER) exceed the output voltage capability of the
coil. With a 40KV coil that could be as large as 0.065 inch, at least for
a short time. However, there are so many variables at work in the voltage
requirement that there is a HUGE gray area in the ideal setting. As such,
it is best not to challenge the upper end of the coil output capability.
If you have a high compression engine, set the gap back a little. If your
engine tends to soil the plugs occasionally, set the gap back a little. If
your plug wires are old, don't push your luck. And my favorite point, if
you like to forget about plug maintainance for a long period of time, set
the starting gap a little smaller to allow for future wear. I find that
the 40KV coil and .035" plug gap is a significant improvement over standard
equipment, does a nice job at that setting, and sees little or no
noticeable improvement with larger settings. I also find from experience
and much extended driving that a .045" gap may occasionally have me pulling
the plugs for check and resetting before I would otherwise like to bother
with it. I'm a bit of a slouch there you know, rather be driving than
tinkering.
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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