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This should be in the technical section and a mod may move it there later.
Here goes:
Detonation is often caused by excessive cylinder pressure at the point of ignition. The air fuel mixture explodes violently rather than being burned.
An increase in compression ratio can increase cylinder pressure
A supercharger or a turbo can increase cylinder pressure as well because it stuffs more air into an engine than a non supercharged engine.
Uusually turbo or supercharged engines have lower compression ratios than a normal engine, to make sure the cylinder pressure does not get too high.
Your buddy would have to reduce the compression ratio of the engine after the supercharger was bolted on. This is done by increasing the volume of the combustion chamber, that is, one makes more room in the cylinder when the piston is all the way up. One can do this by dished pistons, or cylinder heads with a larger chamber, or...sometimes, by a thicker head gasket.
Finally, a leaner air fuel mixture (more air and less fuel) is somewhat more likely to detonate, all other things being equal.
Class dismissed.
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