1. Four Stroke Cycle
Engine Fundamentals

2. Basic Engine Parts

3. Camshaft
Used to open and close valves.

4. Valves
Used to let gases into and out of the combustion chamber.

5. Engine Operation
Fuel is burned inside the engine’s combustion chamber to produce heat and pressure
Engine components convert that pressure into rotating motion

6. Engine Operation

7. Piston Travel Terms: (TDC, BDC)
Top dead center (TDC)
piston is at its highest point in the cylinder
Bottom dead center (BDC)
piston is at its lowest point in the cylinder
Piston stroke
distance the piston slides up or down from TDC to BDC

8. Piston Travel (TDC, BDC)

9. Four-Stroke Cycle
Two complete crankshaft rotations are required to complete the four-stroke cycle
Almost all automobiles use four-stroke-cycle engines

10. 1. Intake Stroke Intake valve is open Exhaust valve is closed
Piston slides down and forms a vacuum in the cylinder which draws fuel and air into the engine

11. 2. Compression Stroke
Piston slides upward and compresses (squeezes) the air-fuel mixture, making it more combustible
Both valves are closed

12. 3. Power Stroke Both valves are closed
Spark plug fires, igniting the air-fuel mixture.
Piston is forced down, rotating the crankshaft

13. 4. Exhaust Stroke Piston moves upward Intake valve is closed
Exhaust valve is open
Burned gases are pushed out the exhaust port

14. Four-Stroke Cycle

15. The End