Hey, I just pulled this off the alt.hi-po.mopars newsgroup. I think it is a
good explanation of the combustion process....
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B. Rhodes wrote...
I think what he meant, is that in a larger bore, the combustion can tend to
take
too long to complete at high rpms. This is part of the reason
multi-sparkplug
heads have been developed; to start the flamefront at two points to increase
the
speed the combustion completes. Longer stroke wouldn't help this simply
because
the bore is still the same width at a specific rpm. If the burn isn't
finished
when the piston gets to the bottom, power is lost. Ideally the flame should
meet
the piston at precisly TDC and be completely finished when the piston
reaches
BDC. This is why timing can be advanced several degrees, starting the fuel
burning before the piston gets to TDC. Spark ping, is simply the flame front
hitting the piston before it gets to TDC and having a helluva collision.
(or, in
the case of detonation caused by a too lean mixture, the fuel actually
detonating, much like a stick of dynamite smacking the crap outta the
piston,
rather than burning nice and evenly. Low octane fuel is actually quite a bit
more explosive than high octane fuel:)
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