Paul Lamar wrote:

That reminds me. If you use a microcomputer to control the waste gate
a whole host of parameters can be used to control the boost.
Intake manifold temp being the primary one but coolant temp, oil temp,
RPM, etc., etc., etc., can be used to insure the engine does not detonate
and/or is not over stressed in any way.

I disagree slightly.  Those parameters can be used as indicators for the operating
regime of the engine (i.e. what's going on inside the chamber right now).  But the
only *certain* way to ensure [note grammar] the engine does not experience
detonation is the GAMI way: sense the pressure in the chamber, detect the
pre-detonation pressure instability, and modify the engine controls to back the
engine away for that operating regime.

For our purposes it is probably sufficient to sense other parameters and
extrapolate a likely engine operating regime, and then manipulate the engine
controls appropriately, but it's important to note that one *must* have two
things: 1. a good model of the engine operating envelope so that the sensed
parameters can be translated into an accurate prediction, and 2. suffice margin in
that model and in our desired operating range so that we can prevent overshooting
the boundary and entering into the Detonation Zone. [cue: ominous music :-)]

When one lacks either of those, engines can go BOOM (as Barry Gardner mentioned).

Russell Kent

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.

Lots of work was done by NACA on this problem back during WW II.
That's is why P38 pilots were told to fly (so to speak) the intake
manifold temp gage. 138 F limit as I recall.

Just one of many papers on the subject.

754.Miller, Cearcy D Relation between spark-ignition engine knock, detonation 
waves, and autoignition as shown by high-speed photography
naca-report-8551946 

Paul Lamar
 
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