A four-stroke petrol engine is an internal combustion engine that operates in four distinct strokes or phases: intake, compression, power, and exhaust. Here's a detailed explanation of each stroke:
1. Intake Stroke:
- The intake valve opens, allowing a mixture of air and fuel (petrol) to be drawn into the cylinder from the carburettor or fuel injector.
- The piston moves downward in the cylinder, creating a vacuum that helps draw in the air-fuel mixture.
2. Compression Stroke:
- The intake valve closes, and the piston starts moving upward, compressing the air-fuel mixture within the cylinder.
- This compression increases the pressure and temperature of the mixture, making it more combustible.
3. Power Stroke:
- At the top of the compression stroke, the spark plug ignites the compressed air-fuel mixture, creating a controlled explosion.
- This explosion generates high pressure and forces the piston downward, driving the crankshaft and producing mechanical work.
4. Exhaust Stroke:
- As the piston reaches the bottom of the power stroke, the exhaust valve opens.
- The piston moves upward, pushing the burnt gases and combustion products out of the cylinder and through the exhaust system.
Repeat:
These four strokes occur in a continuous cycle, with the engine repeating this sequence to generate continuous power. The valve timing and synchronization of the piston movement with the opening and closing of the valves are crucial for efficient engine operation.
