Definition
A system used on some high-output reciprocating aircraft engines that injects a water-and-alcohol mixture into the induction system during high-power operation to cool the fuel-air charge and prevent detonation, allowing the engine to develop maximum power without damage.
Plain English
A way of spraying a water-and-alcohol mix into the engine's air intake during takeoff or other high-power moments. The mixture cools the incoming air and fuel so the engine can run hard without the fuel exploding the wrong way inside the cylinders.
Context Anchor
Seen in discussions of high-performance piston engines, takeoff power, engine cooling, and detonation control.
Derivation
Anti- means 'against.' Detonation here is the technical engine term for an uncontrolled explosion of the fuel-air mixture inside a cylinder (not the smooth, controlled burn the engine needs). Injection refers to spraying a fluid into the engine. So the name describes exactly what the system does: it injects a fluid to fight detonation.
Why Pilots Care
Allows safe use of higher manifold pressures and power settings without engine damage from detonation.
Grounding Statement
At very high power, the engine can get hot enough for the fuel-air charge to burn too violently, and antidetonation injection helps keep that from happening.
Intuition Check
Antidetonation injection is not the same as fuel injection. It adds a detonation-suppressing fluid, usually water, alcohol, or both, to help protect the engine during high-power operation.
Example Sentence 1
The flight engineer armed the antidetonation injection system before takeoff so full power would be available without risking engine damage.
Example Sentence 2
Antidetonation injection let the engine maintain climb power without detonation.