The exhaust emissions from four stroke engines, like other combustion engines, contain significant quantities of greenhouse gases, as well as other forms of air pollution. The major alternative design is the two-stroke cycle. The cylinder wall is a thin sleeve surrounding the piston head which creates a space for the combustion of fuel and the genesis of mechanical energy.įour-stroke engines are the most common internal combustion engine design for motorized land transport, being used in automobiles, trucks, diesel trains, light aircraft and motorcycles. The right blue side is the intake port and the left brown side is the exhaust port. This action expels the spent air-fuel mixture through the exhaust port.įour-stroke cycle used in gasoline/petrol engines: intake (1), compression (2), power (3), and exhaust (4). During the exhaust stroke, the piston, once again, returns from B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft. (the end of the compression stroke) the compressed air-fuel mixture is ignited by a spark plug (in a gasoline engine) or by heat generated by high compression (diesel engines), forcefully returning the piston to B.D.C. At this point the crankshaft has completed a full 360 degree revolution. This is the start of the second revolution of the four stroke cycle. Combustion: Also known as power or ignition.Both the intake and exhaust valves are closed during this stage. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below).
Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C.In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing a partial vacuum (negative pressure) in the cylinder through its downward motion. This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). Intake: Also known as induction or suction.A stroke refers to the full travel of the piston along the cylinder, in either direction. A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft.
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