Question

Number of working strokes per min. for a four stroke cycle engine are ____________ the speed of the engine in r.p.m.

(a) equal to

(b) one-half

(c) twice

(d) four-times

The question was asked during an interview for a job.

Question is from Comparison of Two Stroke S.I. and C.I. Engines topic in chapter Two Stroke Engines of IC Engine

Answer 1

The correct answer is:

(b) one-half

Explanation:

In a four-stroke engine, there are two crankshaft revolutions for every power stroke (one compression and one power stroke). Therefore, the number of working strokes per minute is half the speed of the engine in revolutions per minute (r.p.m.).

For example:

• If the engine is running at 1000 r.p.m., it will have 500 working strokes per minute (one working stroke per two revolutions).

So, the number of working strokes per minute for a four-stroke engine is one-half the engine speed in r.p.m.