Four Stroke Engines

1. Four Stroke Engines How does a canon work?

2. Engine Operation • Gasoline & diesel engines convert chemical energy into mechanical energy

3. A Stroke… • When the piston moves from TDC to BDC, or vice-versa • TDC: Top Dead Center • BDC: Bottom Dead Center • Gasoline and diesel engines have to go through 4 strokes to create power to move the car

4. 1st stroke: Intake stroke • the intake valve opens • the piston moves down

5. Intake Stroke Continued… • As the piston moves down the cylinder… • a mixture of gas and air enters the cylinder • this mixture is 15 parts air to 1 part gas (15:1 air – fuel ratio) • the air & fuel is mixed & delivered by the fuel system – either a carburetor or fuel injection system

6. 2nd Stroke: Compression Stroke • Intake valve closes • Piston moves up the cylinder • When the piston reaches the top of the cylinder, the air & fuel has been squeezed to 150psi

7. 3rd Stroke: Power Stroke • a spark created by the ignition system, jumps the gap at the spark plug & ignites the air/fuel mixture • This causes the burning gases to expand and drive the piston down the cylinder

8. 4th Stroke: Exhaust Stroke • Once the piston reaches the bottom of the cylinder from the power stroke… • The exhaust valve opens • The piston moves up • The burnt gases are pushed out of the cylinder

9. Then what happens? • After the exhaust stroke, the piston begins moving down on another intake stroke, continually repeating the 4 strokes

10. Lets watch one… http://auto.howstuffworks.com/engine1.htm