Paul Lamar wrote:

It is not just pressure in the chamber that causes detonation. Temp
of the charge in the chamber is a big factor. You can have high pressure
with low temp. In some ways they are strongly related of course. For
example the temp of the intake charge increases as the turbo compression
ratio increases. Therefor the effectiveness of the intercooler
is a big factor. Also anti detonation fluid was used to
cool the charge after the air was compressed by the super charger.

Russell Kent wrote:

Sorry, I didn't mean to imply that "pressure in the chamber causes detonation."  Prior
to the onset of detonation, which is a macro-scale effect within the combustion chamber,
there a micro-scale events that cause the combustion chamber pressures to dance all over
the place.  What GAMI's system does is to detect this pre-detonation instability, which
occurs as the engine approaches the regime where detonation occurs, and then adjust the
engine controls to back away from that regime.  The engine control adjustment might be
to enrichen the charge, reduce the boost, reduce the throttle, retard the timing, or
turn on the anti-detonation fluid pump :-)

Russell Kent

How dose GAMI do it. Saab measures the resistance across the spark
plug gap prior to firing the spark plug as I recall. The resistance in
the combustion chamber is going to be a function of the pressure
as air is an insulator. I suppose with a fast enough computer one
could detect high speed variations in  pressure or it could be
pure BS on GAMI's part. That  would not surprise me given their
track record. I mean who is going to replicate the test
set up and destroy an engine to prove them wrong.

Paul Lamar
 
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