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Two stroke engine |
Four stroke engine |
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Numbers of strokes |
The cycle is completed in one complete revolution (180°) of crankshaft or two strokes of a piston. There is one power stroke in each revolution of the crankshaft. | The cycle is completed in two complete revolutions (360°) of crankshaft or four strokes of a piston. There is one power stroke in two revolutions of the crank shaft. |
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Size |
Light and compact | Heavier and bulkier |
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Inlet and outlet system |
Ports are used | Intake and exhaust valves are used |
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Flywheel |
There is a uniform Turning moment diagram so lighter flywheel is used | Turning moment diagram is no so uniform so heavier flywheel is used. |
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Volumetric efficiency |
Lower (less time for induction of charge) | Higher (more time for induction of charge) |
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Thermal efficiency |
Lower | Higher |
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Use |
Scooters, motorcycles etc | Buses, trucks, aeroplanes etc. |