Class 4 (4th Engineer) MEKM 📅 Dec 2024

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) Description of each of the different strokes of the cycle**
In a 4-Stroke engine, the complete operating cycle requires two full revolutions of the crankshaft (720 degrees) for each power stroke. This cycle consists of four distinct piston strokes, each covering 180 degrees of crankshaft rotation, and involving specific valve and piston actions:
1. **Suction (Intake) Stroke:**
* **Piston Movement:** The piston moves downwards from Top Dead Centre (TDC) towards Bottom Dead Centre (BDC).

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