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exhaust valve
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internal-combustion engine: four-stroke cycle Diagram showing the four-stroke cycle of a typical diesel engine, with labeled stages: intake (air enters), compression (air is compressed), power (fuel ignites and pushes piston down), and exhaust (gases exit). Diagram of a gasoline engine showing a cross-section of a piston and cylinder. Key parts such as the spark plug, valves, camshaft, piston, connecting rod, and crankshaft are labeled. Labeled cross-sectional diagram of a V-type gasoline engine for an automobile, showing internal components such as pistons, crankshaft, camshaft, intake and exhaust valves, connecting rods, spark plugs, and intake manifold.
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exhaust valve

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internal-combustion engine: four-stroke cycle
internal-combustion engine: four-stroke cycle An internal-combustion engine goes through four strokes: intake, compression, combustion (power), and exhaust. As the piston moves during each stroke, it turns the crankshaft.

An exhaust valve is a component in an internal-combustion engine that controls the release of burnt gases from the cylinder. It is a type of poppet valve, featuring a stem and a head that seals against a valve seat. When the engine is running, the exhaust valve opens to allow exhaust gases to exit the cylinder, typically during the exhaust stroke.12

The timing of the exhaust valve opening and closing is critical for engine performance. It is controlled by the camshaft, which is synchronized with the crankshaft. For optimal efficiency, exhaust valves are often timed to open slightly before the piston reaches the bottom of its power stroke and to close after the piston has begun its upward compression stroke. This timing helps to utilize the inertia of the exiting gases and ensure thorough scavenging of the cylinder.21

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3 Britannica Sources
  1. gasoline engine - Valves , pushrods , and rocker arms
  2. camshaft
  3. gasoline engine - Two-stroke cycle

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