1. Copyright © PracticalStudent.com The Four Stroke Engine – Whole Engine

2. Copyright © PracticalStudent.com The Four Stroke Engine – Stroke by Stroke

3. Copyright © PracticalStudent.com The Four Stroke Engine - Inventor  The 4 Stroke Engine was invented by Nicholas Otto in 1876.  It was originally designed as a stationary engine.

4. Copyright © PracticalStudent.com The Four Stroke Engine - Intake  Often called the Induction Stroke.  The Inlet Valve is open. The Exhaust Valve is closed.  Air/Fuel mixture is sucked and injected in.  Piston is moving down.

5. Copyright © PracticalStudent.com The Four Stroke Engine - Compression  Inlet and Exhaust Valves closed.  Piston is moving up.  Air/Fuel mixture is being compressed in the cylinder.

6. Copyright © PracticalStudent.com The Four Stroke Engine - Combustion  Often called the Power Stroke.  Inlet and Exhaust Valves closed.  A spark from the Spark Plug ignites the Air/Fuel mixture causing rapid combustion pushing the piston down.

7. Copyright © PracticalStudent.com The Four Stroke Engine - Exhaust  Inlet Valve closed. Exhaust Valve open.  Piston moving up pushing the exhaust gases out.

8. Copyright © PracticalStudent.com The Four Stroke Engine – All Together

9. Copyright © PracticalStudent.com The Four Stroke Engine - Parts See Pgs 224 + 225 (OB) See Pgs 220 + 221 (NB)

10. Copyright © PracticalStudent.com The Four Stroke Engine - Layouts

11. Copyright © PracticalStudent.com The Four Stroke Engine – Inline-4

12. Copyright © PracticalStudent.com The Four Stroke Engine – Boxer-4 / Flat-4

13. Copyright © PracticalStudent.com The Four Stroke Engine – V6

14. Copyright © PracticalStudent.com The Four Stroke Engine - Advantages  Compared to 2 Stroke : Better fuel economy More Torque Better durability Cleaner emissions

15. Copyright © PracticalStudent.com The Four Stroke Engine - Disadvantages  Compared to 2 Stroke : Less powerful Much more complicated Lower revs More expensive