1. Automotive Technology
The Four Strokes:
Intake
Compression
Power
Exhaust

2. Intake Stroke
Notice what the valves are doing. The piston is going downward while the intake valve opens to let the air fuel mixture into the cylinder and the exhaust valve is closed so that it will not leak out.

3. Compression Stroke
The piston moves back upward and the valves are both closed to trap and compress the air-fuel mixture

4. Now BOTH valves remain closed so when the spark plug ignites the mixture, all of the force pushes the piston downward.
Power Stroke

5. Exhaust Stroke
Now the piston is on the way back UP while the exhaust valve opens and the intake valves remains closed.
This lets the exhaust escape through the exhaust valve and out into the exhaust system. The cycle then begins with the intake stroke again.

6. Name the stroke:
What are the valves doing and what direction is the piston moving?
Exhaust Stroke
The intake valve is closed while the exhaust valve opens. The piston is moving upward.

7. What are the valves doing and which direction is the piston moving?
Intake Stroke
The intake valve is open, and the exhaust valve is closed. The air-fuel mixture is coming into the cylinder and the piston is moving downward.

8. Compression Stroke
What are the valves doing and which way is the piston moving?
Both valves are closed and the piston is moving upward.

9. Power Stroke
What are the valves doing and which way is the piston moving?
Both valves are closed , the spark plug ignites the air-fuel mixture. The piston is forced downward.

10. The Four Strokes are: Intake (Suck) Compression (squeeze) Power (Bang)
Exhaust (Blow)

11. The four stroke cycle