William Eastman wrote an excellent article on this. However, there are
a couple of additional points that should be made:
Valve Overlap -- all other things equal, minimal valve overlap would
be good, however, all other things are not equal and (my understanding
is that) valve overlap allows a greater charge of Fuel/Air mixture --
hence more pressure.
Detonation -- it is important to distinguish between high-speed knock
and low speed knock. High speed knock is not audible and will destroy
an engine in seconds. This is *not a good thing*. High speed knock
causes a rapid increase in temperature, which causes more knock,
which... End of engine!
Low speed knock is not such a problem. In the early '80s, I was
working on a knock-detection project with F*rd's engine designers in
the UK. Their main concern with low speed knock was owner complaints
about the noise! Generally more power will be produced under light
knock conditions.
Flames, corrections, clarifications, anyone?
Regards,
Simon
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