1. Intake Stroke:
- The intake valve opens, and the piston moves downward in the cylinder.
- This creates a low-pressure area, drawing in air and fuel mixture (in gasoline engines) or air (in diesel engines) through the open intake valve.
2. Compression Stroke:
- Both the intake and exhaust valves are closed.
- The piston moves upward in the cylinder, compressing the air-fuel mixture (or air in diesel engines) to a much smaller volume.
- This increases its pressure and temperature.
3. Power Stroke:
- At the top of the compression stroke, the spark plug ignites the compressed air-fuel mixture in gasoline engines (or the high pressure and temperature cause the diesel fuel to self-ignite in diesel engines).
- This creates a rapid expansion of gases, driving the piston downward with great force.
- This downward motion of the piston generates power and is the main power-producing stroke of the engine.
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 out of the cylinder through the open exhaust valve.
These four strokes continuously repeat, with the crankshaft converting the reciprocating motion of the piston into rotary motion, which is then used to power various devices or machines.
In summary, a four-stroke engine operates by drawing in an air-fuel mixture or air, compressing it, igniting it to produce power, and then expelling the burnt gases through a series of four distinct strokes.
