Question

A two stroke cycle gives ____________ the number of power strokes as compared to four stroke cycle engine at the same engine speed.

• A. Half
• B. Same
• C. Double
• D. Four times

Hint:

Think about how many crankshaft revolutions each cycle needs to complete one power stroke.

Answer 1

The Correct Option is C

Take a concrete example. Suppose the engine runs at 3000 rpm.

A four stroke engine needs 2 revolutions per cycle, so it gives one power stroke every 2 revolutions. At 3000 rpm that is $3000/2 = 1500$ power strokes per minute.

A two stroke engine completes its cycle in just 1 revolution, since intake and exhaust happen through ports during the same revolution that carries the compression and power strokes. So it gives one power stroke every single revolution, which at 3000 rpm means $3000$ power strokes per minute.

Comparing the two, $3000$ is exactly double $1500$, at the same rpm.

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