The camshaft rotates _____ degrees during one four-stroke cycle.
The correct answer and explanation is :
Correct Answer: The camshaft rotates 180 degrees during one four-stroke cycle.
Explanation (300 words):
To understand why the camshaft rotates 180 degrees during a four-stroke cycle, we need to look at how a four-stroke internal combustion engine works and the relationship between the crankshaft and the camshaft.
The four strokes of a typical gasoline or diesel engine are:
- Intake stroke – the intake valve opens, and the piston moves down to draw in the air-fuel mixture.
- Compression stroke – the intake valve closes, and the piston moves up to compress the mixture.
- Power stroke – the spark plug ignites the mixture, forcing the piston down.
- Exhaust stroke – the exhaust valve opens, and the piston moves up again to expel the exhaust gases.
These four strokes occur over two complete revolutions (720 degrees) of the crankshaft. This is because each stroke requires half a crankshaft revolution, and four strokes equal two full turns of the crankshaft.
The camshaft is responsible for opening and closing the intake and exhaust valves at the correct times. Since each cylinder only needs the valves to open and close once every two revolutions of the crankshaft (i.e., every 720 degrees), the camshaft must rotate at half the speed of the crankshaft.
Therefore, during one complete four-stroke cycle (720° crankshaft rotation), the camshaft rotates only 360 degrees.
However, the question asks how much the camshaft rotates during one revolution of the crankshaft, which is half of a four-stroke cycle. Since the camshaft turns at half the speed of the crankshaft, then for one 360° revolution of the crankshaft, the camshaft rotates 180 degrees.
In summary:
- 1 four-stroke cycle = 720° crankshaft rotation
- Camshaft rotates at half the speed = 360° per cycle
- Therefore, during 1 crankshaft revolution (360°), camshaft = 180° rotation.
