Definition
A condition in which a turbocharged or supercharged engine is operated at a manifold pressure higher than the maximum allowed by the manufacturer. Overboost can cause detonation, excessive cylinder pressures, and serious internal engine damage.
Plain English
Pushing a turbocharged or supercharged engine harder than it is designed to handle, so that the air pressure being forced into the cylinders exceeds the published limit.
Context Anchor
You may see this term when learning about high-performance piston engines, takeoff power settings, and engine operating limits.
Derivation
Combines the prefix 'over-' (beyond, excessive) with 'boost' — the term used for the extra manifold pressure produced by a turbocharger or supercharger above normal atmospheric pressure. So 'overboost' literally means boosting beyond the allowable amount.
Why Pilots Care
It can lead to engine damage or failure if not corrected promptly.
Intuition Check
Overboost is not simply “extra power.” It means the engine has exceeded a pressure limit and is being operated outside its safe range.
Example Sentence 1
On takeoff, the pilot advanced the throttle smoothly to avoid an overboost as the turbocharger spooled up.
Example Sentence 2
Failure of the automatic wastegate can cause an overboost condition.