Exam Question
Explain how the following affect the performance of a Marine Diesel engine:
(a) Stretch in camshaft chain (6)
(b) Incorrect exhaust valve tappet clearance (5)
(c) Worn fuel pump plungers(5)
Class 4 (4th Engineer)
MEKM
📅 Sep 2022
Reference Answer
### (a) Effects of Stretch in Camshaft Chain (6 Marks)
A camshaft drive chain transmits the rotational motion and timing from the crankshaft to the camshaft. A stretched chain directly compromises this timing relationship, leading to retarded (delayed) operation of all camshaft-driven components.
**1. Principle of Operation & Effect of Stretch:**
* The camshaft rotates at half the crankshaft speed in a 4-stroke engine and at the same speed in a 2-stroke engine. Its precise angular position relative to the crankshaft determines the timing of fuel injection and valve operation.
A camshaft drive chain transmits the rotational motion and timing from the crankshaft to the camshaft. A stretched chain directly compromises this timing relationship, leading to retarded (delayed) operation of all camshaft-driven components.
**1. Principle of Operation & Effect of Stretch:**
* The camshaft rotates at half the crankshaft speed in a 4-stroke engine and at the same speed in a 2-stroke engine. Its precise angular position relative to the crankshaft determines the timing of fuel injection and valve operation.
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