Like many other 'go-faster' bits they add little if anything to a generally
factory spec car in good condition other than cost and the opportunity for a
bit of bar-room bragging. Where they *can* make a difference is in marginal
conditions like cold and damp, poor state of tune, weak battery etc. There
have been such devices around since the 70s and earlier, and one passive
device I was aware of reckoned to deliver multiple high-frequency sparks
from a standard HT system by the use of multiple air gaps. The principle
worked - on a couple of occasions I got my Mini going by wiggling the HT
lead a little way out of the coil while someone else cranked it, which
always got it going whereas previous cranking hadn't.
In theory twin-spark systems can complete the burn in half the time and so
give a bit bigger bang initially, but since I have only seen them in Alfa
Romeos I rather suspect it was a case of 'if the first spark doesn't set it
off the 2nd will'. If it made any difference at all then all performance
cars would have had them for years.
PaulH.
----- Original Message -----
> I once read a piece which said that high voltage coils (big
> sparks, multiple sparks etc) were unnecessary and just fodder for the
> I-wanna-go-faster-so-give-me-racing-stripes fraternity.
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