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Detonation occurs any time you have enough heat and pressure to cause a pocket of fuel and air to spontaneously "detonate". It occurs after the spark has ignited the mixture but before the flame front reaches and ignites the whole combustion chamber. Excessively lean AFR's or too much ignition advance cause detonation. Either one generates excessive heat, some of which is blown out through the exhaust and some of which is retained in the combustion chamber.
Theres that and theres preignition. Preignition occurs when you have a hot spot that ignites the fuel and air before the spark is fired. This generates extreme and unsustainable amounts of heat.
The problem with this is that theres nothing regulating cylinder filling other than the volumetric efficiency of your engine at any given RPM. The realistic limit for lean running under any kind of load is about 16:1. It wont run much at all leaner than 20:1. Its going to run wide open all the time, and for it to run efficiently its going to require reasonable AFR's. You know what happens when it leans out under load. Heat sinks and oil spray nozzles wont keep that from happening. All you can do is give it enough fuel to keep from melting itself down.
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