Class 4 (4th Engineer) MEKM 📅 Aug 2025

Exam Question

(a) In a 4-Stroke engine, describe each of the different strokes of the cycle. (6)

(b) Draw 4-Stroke timing diagram describing the complete cycle.

Explain how each stroke is completed with action of crank travel and the inlet-exhaust valves. (10)

Reference Answer

### (a) The Four Strokes of a 4-Stroke Cycle
A four-stroke engine completes its operating cycle in four distinct strokes of the piston, which corresponds to two full revolutions of the crankshaft (720°). The strokes are as follows:
#### 1. Suction Stroke (Intake)
* **Piston Travel:** Top Dead Centre (TDC) to Bottom Dead Centre (BDC).

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