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POWER stroke: this is the start of the second revolution of
the engine. While the piston is close to Top Dead Center,
the compressed air–fuel mixture in a gasoline engine is
ignited, usually by a spark plug, or fuel is injected into the
diesel engine, which ignites due to the heat generated in
the air during the compression stroke. The resulting
massive pressure from the combustion of the compressed
fuel‐air mixture forces the piston back down toward
bottom dead center.
Detail
Piston moves from TDC to BDC
Intake valve closed
Exhaust valve closed
Rapid burning causes rapid rise in temperature.
Rapid rise in temperature causes increased pressure.
Pressure induces a force on the piston.
Force on piston produces torque on crankshaft.
540 degrees rotation
EXHAUST stroke: during the exhaust stroke, the piston
once again returns to top dead center while the exhaust
valve is open. This action evacuates the burnt products of
combustion from the cylinder by expelling the spent fuel‐
air mixture out through the exhaust valve(s).
Detail
Piston moving from BDC to TDC.
Intake valve closed
Exhaust valve open
Waste gasses are expelled from the cylinder.
720 degrees of rotation
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