[s-cars] S6 pinging woes - the continuation

Brett Dikeman brett.dikeman at gmail.com
Tue Jul 28 11:21:12 PDT 2009

On Tue, Jul 28, 2009 at 12:50 PM, Taka Mizutani<t44tqtro at gmail.com> wrote:
> You've just contradicted yourself, Brett- if the fuel/air charge ignites
> prematurely, you get a large increase in cylinder pressure, which causes all
> sorts of bad things to happen to the engine.


PRE ignition is a NORMAL combustion event that occurs EARLY.  Because
it occurs EARLY, the combustion chamber is under less compression, so
flame front speed is lower...most likely max pressure and temperature
are lower than a normal combustion event at full compression.
Preignition is bad because of how the force generated from combustion
is applied.

DETONATION is an ABNORMAL combustion event where multiple ignition
points or spontaneous combustion of the entire fuel-air charge occurs,
resulting in pressures that are double or more from normal maximums.
An exaggerated example: compare the difference between a cup of gas on
the floor of a room burning, and the same cup of gas, vaporized in the
room for a stochiometric mix.  One sets off the smoke detector.  The
other blows the room apart.


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