Power stroke frequency — two-stroke vs four-stroke at the same engine speed Compared with a four-stroke engine running at the same revolutions per minute, a two-stroke cycle engine delivers how many power (working) strokes per minute per cylinder?

Introduction / Context:
The frequency of power events affects torque smoothness and specific power. Two-stroke engines complete a thermodynamic cycle every revolution, while four-stroke engines require two revolutions. This directly determines the count of power strokes per minute at a given speed.

Given Data / Assumptions:

• Same crankshaft speed for both engines.
• Comparison per single cylinder to avoid cylinder-count effects.

Concept / Approach:
In a two-stroke, the cycle is completed in one revolution (360 degrees), delivering one power stroke per revolution. In a four-stroke, one power stroke occurs every two revolutions (720 degrees). Therefore, at the same rpm, a two-stroke has twice as many power strokes per minute per cylinder.

Step-by-Step Solution:
Two-stroke: power strokes per minute = N.Four-stroke: power strokes per minute = N/2.Ratio (two-stroke : four-stroke) = N : N/2 = 2 : 1.Hence, two-stroke delivers double the power strokes per minute.

Verification / Alternative check:
Timing diagrams and cycle descriptions in standard texts confirm the revolution requirement per cycle for each architecture.

Why Other Options Are Wrong:
“Same” and “half” contradict the fundamental cycle counts. “Four times” would require a power stroke every half revolution, which does not occur.

Common Pitfalls:
Conflating number of power strokes with actual brake power, which also depends on trapped mass, scavenging quality, and efficiency.

Final Answer:
Double