The crankshaft rotates_____ degrees during one four-stroke cycle.
The correct answer and explanation is :
Correct Answer: The crankshaft rotates 720 degrees during one four-stroke cycle.
Explanation (300 words):
The four-stroke cycle is a common internal combustion engine process used in gasoline and diesel engines. It includes four distinct strokes: intake, compression, power (combustion), and exhaust. These strokes occur over two full revolutions of the crankshaft, which is equal to 720 degrees (360 degrees per revolution × 2).
Here’s how it works step by step:
- Intake Stroke (0° to 180° crankshaft rotation):
The intake valve opens, and the piston moves downward. This downward motion draws an air-fuel mixture (in gasoline engines) or air (in diesel engines) into the combustion chamber. This stroke begins at top dead center (TDC) and ends at bottom dead center (BDC), completing 180° of crankshaft rotation. - Compression Stroke (180° to 360°):
With both intake and exhaust valves closed, the piston moves upward from BDC to TDC. This compresses the air-fuel mixture, increasing its pressure and temperature, which is essential for efficient combustion. Another 180° of crankshaft rotation occurs here. - Power Stroke (360° to 540°):
At the start of this stroke, the spark plug (in gasoline engines) ignites the compressed air-fuel mixture, or fuel is injected (in diesel engines). The resulting explosion forces the piston downward, delivering power to the crankshaft. This stroke accounts for another 180° of crankshaft movement. - Exhaust Stroke (540° to 720°):
Finally, the exhaust valve opens, and the piston moves back up to expel the burnt gases from the combustion chamber. This final stroke completes the cycle with another 180°, totaling 720° for all four strokes.
Thus, a complete four-stroke cycle requires two full crankshaft revolutions (720°) to complete all four piston strokes.
