Re: knock

[AKress1948@aol.com]

Bob gives a good explanation of what & why knock, then raises question of
knock at low rpm w/ wide open throttle.  Detonation is caused by the mixture
ahead of the flame front heating up (from the flame front) to the point that
it self ignites, burns back to the flame front - the resulting pressure or
shock wave causes the knock.   The rate of combustion in the cylinder varies
with conditions in the chamber.  It is slowest in a stagnant condition, and
increases ~ linearly with increase in turbulance which tends to increase
linearly with engine speed.  The net effect actually is for the duration of
combustion to be fairly constant over a given crank angular movement.  At high
rpms,  the mechanical parts of the system are moving so quickly that the
piston is on the right side of it's stroke, and valves are opening, and the
combustion phase concludes before there are time and heat available for the
charge to self ignite.  However,  in a low rpm condition the mechanical parts
are moving slower  while the chemical parts (flame front / self ignition) are
working at their usual (fairly) constant speed, so that there is plenty of
time for this whole detonation process to occur.  
This whole problem is worsened by a slightly rich condition - perhaps that
explains the WOT portion of your question.
hope this helps.
Andy