Definition
The hot, high-pressure gases produced by the combustion of the fuel-air mixture in an engine's cylinders, expelled through the exhaust system after the power stroke. In a turbocharged engine, these gases retain enough energy to spin a turbine, which in turn drives a compressor that pressurizes the engine's intake air.
Plain English
The hot gases left over after fuel burns inside the engine. They flow out through the exhaust pipe, and in a turbocharged engine they're put to work spinning a small turbine before they leave the airplane.
Context Anchor
Seen in turbocharging discussions, engine operation, exhaust system inspections, and maintenance concerns involving leaks, heat, or turbocharger performance.
Derivation
From Latin exhaurire, meaning 'to draw out or empty.' The exhaust is what the engine has finished with and is drawing out of the cylinders.
Why Pilots Care
In turbocharged engines these gases spin the turbine that compresses intake air, allowing the engine to produce sea-level power at higher altitudes.
Intuition Check
Do not think of exhaust gases as just visible smoke. Exhaust gases are often invisible, very hot, and still carry enough energy to drive part of a turbocharging system.
Example Sentence 1
The turbocharger uses energy from the engine's exhaust gases to compress incoming air, restoring sea-level power at altitude.
Example Sentence 2
Back pressure in the exhaust system can reduce how effectively exhaust gases drive the turbocharger.