This is some good information on the differences between pre-ignition and detonation:
http://www.contactmagazine.com/Issue...ineBasics.html
Here is a snippet: "Engine test data determines how much compression an engine can have and run at the optimum spark advance.
For emphasis, the design compression ratio is adjusted to maximize efficiency/power on the available fuel. Many times in the aftermarket the opposite occurs. A compression ratio is "picked" and the end user tries to find good enough fuel and/or retards the spark to live with the situation...or suffers engine damage due to detonation"