What is detonation in a reciprocating engine?

Detonation in a reciprocating engine refers to the phenomenon where there is a premature ignition of the air-fuel mixture during the compression stroke. This leads to an uncontrolled and explosive combustion event rather than the intended smooth burning of the fuel. The resulting rapid pressure rise can cause engine knocking, which can be damaging to engine components.

In a properly functioning engine, the air-fuel mixture ignites at the appropriate time, just after the piston passes top dead center. However, when detonation occurs, it creates a different combustion wave that can lead to increased stress on pistons, rods, and bearings. Recognizing this scenario is essential for engine performance and longevity.

The other options relate to timing and combustion efficiency but do not capture the essence of what detonation implies in the context of the engine's operation and resultant effects.