Correct Answer - Option 3 : produces more power
Concept:
Two-stroke engines: In this engine, one power stroke is obtained in each revolution of the crankshaft
Four-stroke engines: In this type of engine, one power stroke is obtained in two revolutions of the crankshaft
Advantages of the two-stroke engine over four-stroke engine are
- Low cost
- More uniform torque and hence lighter flywheel is needed
- Because of one power stroke for one revolution, power produced for same size of engine is more
- Lightweight and simplicity due to the absence of the valve mechanism.
Four Stroke Engine
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Two Stroke Engine
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Four operations (suction, compression, power, and exhaust) take place in the four strokes of the piston
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The four operations take place in two strokes of the piston
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It gives one power stroke in the four strokes, i.e. in two revolutions of the crankshaft. As such three strokes are idle strokes
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The power stroke takes place in every two strokes i.e. one power stroke for one revolution of the crankshaft
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Due to more idle strokes and non-uniform load on the crankshaft, a heavier flywheel is required
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The engine has a more uniform load as every time the piston comes down it is the power stroke. As such a lighter flywheel is used
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The engine has more parts such as valves and its operating mechanism. Therefore, the engine is heavier
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The engine has no valves and valve operating mechanism; Therefore, it is lighter in weight.
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The engine is costlier as it has more parts
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The engine is less expensive as it has a lesser number of parts
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The engine efficiency is more as the charge gets completely burnt out. Consequently, fuel efficiency is more
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The efficiency is less. A portion of the charge escapes through the exhaust port, and because of this, the fuel efficiency is less.
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