FOUR STROKE ENGINE

How a four stroke engine works

- intake
- compression
- power (combustion)
- exhaust

B.D.C = bottom dead centre
T.D.C = top dead centre

wet sump = four stroke
dry sump = 2 stroke

oil - lubricates
     - heat distribution




1 - air comes through the air manifold and is taken through to the combustion chamber. in this chamber its mixed with fuel and becomes a fuel and air mixture. air is open, exhaust is closed and piston is T.D.C.
2 - the fuel and air mixture is now compressed as the piston rises up. air intake closed, exhaust closed, piston is moving up.
3 - the fuel and air mixture is compressed and the spark plug makes a spark that makes the mixture combust, pushing the piston back down. air intake closed, exhaust closed, piston is T.D.C and plug makes spark
4 - as the piston reaches B.D.C again the combusted gas is released through the exhaust. air intake closed, exhaust open, piston is B.D.C.