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On 28 Oct 97, scott a keck wrote:
> On Mon, 27 Oct 97 08:05:15 EST parkkj@orion.crd.ge.com (Keith Park)
> writes:
> >Adding Comp ign with higher energy with the stock squatty small
> >distributor cap is asking for problems concerning breakdown and
> >arc-over from the short distances in the cap... Right??
> >
> >Ever see a high evergy cap on a late model car? there HUGE!
> Naw, we are not talking 60,000 to 80,000 volts like new systems.
There's a bisic misconception going on here. The voltage you see
advertized for these systems is the peak voltage it is capable of.
When the system fires the voltage rises; it's not instantaneous, just
very fast. When the voltage reaches the point where something will
flash over the voltage rise is halted and we have a spark. With luck
this spark occurs at the spark plug. With normal gaps this voltage
is around the 20-30 kV range.
To get a spark at the spark plug you need two things: a system that
can deliver at least the amount of voltage you need to fire the plug,
and cables that won't offer a flashover to ground at a lower voltage.
The HE systems on many late cars are used along with wider spark plug
gaps. These increase the flashover voltage. The spark plug
flashover voltage is also affected by the pressure and mixture ratio
at the gap at the moment of ignition. This means that it is
indirectly affected by rpm, throttle position, compression ratio,
carburation, and the valve cam. The ignition system just needs to be
capable ot sourcing a voltage in excess of the maximum the spark
plugs will ever require.
Jim
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Melissa Kepner Jim Adney
Laura Kepner-Adney
jadney@vwtype3.org
Madison, Wisconsin
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