Power strokes in a two-stroke engine For a two-stroke cycle engine, the number of working (power) strokes per minute is __________ the engine speed in revolutions per minute (r.p.m.).

Introduction / Context:
Cycle timing directly determines how often an engine delivers a power stroke. This affects specific power and helps explain why two-stroke engines achieve higher firing frequency than four-strokes of the same speed.

Given Data / Assumptions:

• Ideal two-stroke cycle: one power stroke per crank revolution.
• Engine speed = N r.p.m.
• No misfires and steady operation.

Concept / Approach:

In a two-stroke engine, the cycle completes in two strokes (one revolution). Therefore, each revolution includes a power event. Consequently, the number of power strokes per minute equals the rotational speed in revolutions per minute.

Step-by-Step Solution:

Verification / Alternative check:

By contrast, a four-stroke requires two revolutions per cycle, yielding N/2 power strokes per minute—useful as a check against the two-stroke result.

Why Other Options Are Wrong:

Half, twice, or four times do not match the one-power-stroke-per-revolution nature of two-strokes.

Common Pitfalls:

Confusing “firing events” with “cylinder count” in multi-cylinder engines. Total engine firings per minute equal per-cylinder firings multiplied by the number of cylinders.

Final Answer:

equal to