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3. Intake and Scavenge of 2-cycle engine

2-cycle engine, different from ordinary four-cycle engine, has simple construction without intake valve and exhaust valve. In case of 2-cycle engine, intake and exhaust have an effect on performance; therefore, various methods have been adopted.
As shown below, regarding intake, the most common are piston valve type and lead valve type.
Also, regarding scavenge, most of them are currently loop type (Schnurle type). Also, use of a third port, and other methods are employed for this purpose.


 A. Piston Valve Type intake Method Intake port provided at cylinder will open and close by piston skirt. Opening and closing timing of intake is at top dead center.  B. Lead Valve Type Intake Method Lead valve will open and intake will take place by negative pressure inside of crank case when piston moves up.
C. Schnurle Type Exhaust
Scavenging takes place by exhausting combustion gas from exhaust port by colliding and inverting airflow from scavenge port provided at cylinder wall.

4. Engine Performance

A performance curve is presented to see performance of engine at a glance.
The figure shows revolution per minute (rpm) on horizontal axis, and output (PS), torque (kg-m) and vertical axis and fuel consumption volume per hour on vertical axis.



Torque or turning force T (kg-m) is force to turn shaft. Assuming pulling force F kg of a rope wound around a pulley with radius R m, torque is T = F x R kg-m
Horsepower (PS) is unit of work to turn the shaft with torque T (kg-m) per minute. In case of N rpm,




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【参】BSI-EN:フッターナビ