A 2-stroke engine is a type of internal combustion engine that completes a power cycle with only two strokes (up and down movements) of the piston, compared to the four strokes of a 4-stroke engine.
In a 2-stroke engine, the intake, compression, combustion, and exhaust processes occur within these two strokes:
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Upward Stroke (Compression & Intake): As the piston moves upward, it compresses the air-fuel mixture in the cylinder. At the same time, it creates a vacuum in the crankcase, drawing in a fresh air-fuel mixture through the intake port.
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Downward Stroke (Power & Exhaust): Near the top of the stroke, the compressed mixture is ignited, forcing the piston downward. As the piston nears the bottom of the stroke, it uncovers the exhaust port, allowing exhaust gases to escape. Simultaneously, the downward motion forces the pre-compressed air-fuel mixture from the crankcase into the cylinder through the transfer port.
Because the 2-stroke engine fires once every revolution, theoretically, it can produce more power than a comparable 4-stroke engine. However, 2-stroke engines often have poorer fuel efficiency and higher emissions due to incomplete combustion and the loss of some fuel mixture during the scavenging process.
