two-stroke cycle
Quick Summary
The two-stroke cycle is a working cycle for a piston in an internal combustion engine. It completes its cycle in two strokes, requiring only one crankshaft revolution. During the first stroke, the piston compresses the fuel mixture on one side while simultaneously receiving thrust from previously compressed gases on the other. In the second stroke, the piston draws in a fresh fuel charge on one side while expelling burnt gases on the other.1
This design is often used in smaller gasoline engines, such as outboard motors and portable generators. However, two-stroke engines can be noisy and contribute to air pollution due to emissions. They also tend to have lower fuel economy compared to four-stroke engines because some fresh charge can be lost through the exhaust ports.2
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