1. The Four Stroke Piston Engine
1x60m w/ FSgt Aikens
EO M232.03

2. Importance
The importance might not be obvious unless you already know what the stroke cycle is.
Essential, this is how the engine works.
This is important if you are interested in being someone who works with engines, like a mechanic or engineer, or if you want to operate an engine, like a pilot.

3. The Stroke Cycle
The parts of the engine work in a repeating cycle to turn the crankshaft
In most engines, this cycle has four strokes
During these four strokes the crankshaft completes two turns

4. The Stroke Cycle The strokes are: Intake Compression Power Exhaust
Where air and fuel is brought into the cylinder
The piston moves up compressing the mixture
The mixture is ignited, the explosion pushing the piston down
The piston moves back up, pushing out the exhaust gasses

5. Intake
The piston is moving down and the intake valve is open to allow the fuel/air mixture to be pulled in.
The exhaust valve is closed.

6. Compression The piston now moves up, compressing the mixture
Compressing the air forces
more air particles to be
closer together and makes
for a cleaner, bigger
explosion.
Both valves are closed

7. Power
The piston is pushed back down by the explosion created by the spark plug
Both valves are closed
This creates the power in
the engine.

8. Exhaust
The piston is moving back up, pushing the burnt leftovers out of the engine.
The exhaust valve is open
After this,the process repeats

10. Quiz time What happens in the power stroke?
The spark goes off and the piston is pushed down.
How many times would the crankshaft rotate if the spark plug goes off twice? 4
Why is there an exhaust stroke?
To remove the burnt ashes from the engine to restart the cycle.

11. Timing
Valve timing is provided by the camshaft, a rod with bumps on it that push open the correct valve at the correct time. The camshaft is connected to the crankshaft, so it is always in time with the engine.

12. Timing
Additionally, the spark plug is electronically timed with a distributer and magnetos.
The spark is actually timed to go off while the piston is rising, to give the mixture time to burn completely.

13. Quiz time When is the spark timed to happen?
Just before the piston hit the top
What stroke is that?
Power
What does the camshaft do?
Times valve opening/closing

14. Conclusion
That was EO M232.03