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There isn't really a "predetonation", it's either detonation or preignition.
Combustion temps do not continue to increase over (leaner) than stoichiometry.
The detonation threshold gets more critical with increasing manifold pressure.
(numbers are approximate)
<750 millibars, stoichiometric and leaner is generally safe, only the flame speed slows (if leaned out) thus timing must be increased to compensate if running on the lean side.
>750 millibars, requires richer than 14.7; latent heat of evaporation plays a role in detonation resistance so under this circumstance, the octane vs afr arguement is valid.
I think it could be an opamp and something to shift timing, or maybe something to reduce map signal so it runs leaner and with more timing then it normally would. Obviously, this could be more stress on the engine.
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