FAA Powerplant Written Practice Test

What does detonation in an engine typically result in?

1. Piston damage

2. Oil contamination

3. Increased fuel efficiency

4. Reduced engine temperature

The correct answer is: Piston damage

Detonation in an engine is characterized by an uncontrolled explosion of the air-fuel mixture in the combustion chamber, which occurs instead of a smooth and controlled burn. This phenomenon can create extremely high-pressure waves within the cylinder, leading to significant mechanical stress. The most common consequence of detonation is damage to various engine components, particularly the pistons. This damage can manifest as erosion, cracking, or even complete failure of the piston, as well as issues in other parts such as the cylinder head and the valves due to the excessive pressure and heat generated. In contrast, oil contamination is not a direct result of detonation but rather can stem from separate issues like worn piston rings or gaskets. Increased fuel efficiency is generally incompatible with detonation, as detonation indicates an inefficient combustion process. Reduced engine temperature is also unlikely, as detonation typically leads to an increase in temperature due to the violent and rapid combustion of the fuel mixture. Therefore, the outcome of detonation directly aligns with the possibility of piston damage, making it the correct choice.