Advantages and Disadvantage of Two-Stroke Over Four-Stroke Cycle Engines

Advantages and Disadvantage of Two-Stroke Over Four-Stroke Cycle Engines Points : Advantages and Disadvantage of Two-Stroke Over Four-Stroke Cycle Engines Advantages

1. A two-stroke cycle engine gives twice the number of power strokes to the four stroke cycle engine at the same engine speed. Theoretically, a two-stroke cycle engine should develop twice the power as that of a four-stroke cycle engine. But in actual practice, a two-stroke cycle engine develop 1.7 to 1.8 times (greater value for slow speed engines) the power developed by four-stroke cycle engine of the same dimensions and speed. This is due to lower compression ratio and effective stroke being less than the theoretical stroke.
2. For the same power developed, a two-stroke cycle engine is lighter, less bulky and occupies less floor area. Thus it makes a two-stroke cycle engine suitable f marine engines and other light vehicles.
3. As the number of working strokes in a two-stroke cycle engine are twice than the four-stroke cycle engine, so the turning moment of a two-stroke cycle engine is more uniform. Thus it makes a two-stroke cycle engine to have a lighter flywheel and foundations. This also leads to a higher mechanical efficiency of a two-stroke cycle engine.
4. The initial cost of a two-stroke cycle engine is considerably less than a four-stroke cycle engine.
5. The mechanism of a two-stroke cycle, engine is much simpler than a four-stroke cycle engine.
6. The two-stroke cycle engines are much easier to start.

Disadvantages

1. Thermal efficiency of a Iwo-stroke cycle engine is less than that a four-stroke cycle engine, because a two-stroke cycle engine has less compression ratio than that of a four-stroke cycle engine.
2. Overall efficiency of a two-stroke cycle engine is also less than that a four-stroke cycle engine because in a two-stroke cycle, inlet and exhaust ports remain open simultaneously for some time. Inspite of careful design, a small quantity of charge is lost from the engine cylinder.
3. In case of a two-Stroke cycle engine, the number of power stroke are twice as those of a four-stroke cycle engine. Thus the capacity of the cooling system must be higher. Beyond a certain limit, the cooling capacity offers a considerable difficulty Moreover, (here is a greater wear and tear in a two-stroke cycle engine.
4. The consumption of lubricating oil is large in a two-stroke cycle engine because of high operating temperature.
5. The exhaust gases in a two-stroke cycle engine creates noise, because of short time available for their exhaust