If the engine senses detonation, it will retard the timing to prevent detonation. If it does need to do this under high load conditions, the result of the retarded timing would be less energy being extracted from the fuel and thus a decrease in performance and efficiency.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record