Stroke 3 of 4 'Bang': While the piston is at or close to Top Dead Center, the compressed air–fuel mixture is ignited, usually by a spark plug (for a gasoline or Otto cycle engine) or by the heat and pressure of compression (for a diesel cycle or compression ignition engine). Stroke 2 of 4 'Squeeze': With both intake and exhaust valves closed, the piston returns to the top of the cylinder compressing the fuel-air mixture. A mixture of fuel and air is forced by atmospheric (or greater) pressure into the cylinder through the intake port. Stroke 1 of 4 'Suck': On the intake or induction stroke of the piston, the piston descends from the top of the cylinder to the bottom of the cylinder, reducing the pressure inside the cylinder. A stroke refers to the full travel of the piston from Top Dead Center (TDC) to Bottom Dead Center (BDC). The cycle begins at top dead center (TDC), when the piston is farthest away from the axis of the crankshaft. The four strokes refer to intake, compression, combustion (power), and exhaust strokes that occur during two crankshaft rotations per working cycle of the gasoline engine and diesel engine.Ī less technical description of the four-stroke cycle is, 'Suck, Squeeze, Bang, Blow' Today, internal combustion engines in cars, trucks, motorcycles, aircraft, construction machinery and many others, most commonly use a four-stroke cycle. The cylinder wall is a thin sleeve surrounded by cooling water. The right blue side is the intake and the left yellow side is the exhaust. Four-stroke cycle used in gasoline engines.

4 stroke internal combustion engine