Four stroke engine

How does a four stroke engine work? Name the cycles ,I want to know what the piston is doing and the valves on each stroke. 


1. Intake - The piston is moving down, intake valve open to drawn the air-fuel mixture into the cylinder.
2. Compression - The piston is moving up to compress the air-fuel mixture in the cylinder, both valves closed, 
3. Power - The piston is moving down by the force of combusted air-fuel mixture, both valves closed.
4. Exhaust - The piston is moving up to force the burnt gases out through the open exhaust valve.

Who and what year was the  four stroke engine invented.

Nikolaus August Otto (1832～1891)

German engineer, invented the first four-stroke engine in 1876.


What is the purpose of the crankshaft,camshaft,vavles collects(keepers),valve sterm seals,head gasket,pistons,piston rings name them all, cambelt,flywheel?


1. Crankshaft - With a crank for each cylinder, connects the piston through connecting rod, turns the piston up and down(straight-line) motion into rotary motion.

2. Camshaft - Controls the timing of intake and exhaust valves open and close. 

3. Valves keepers - The keeper has two opposite fixed ends pressed against a valve seat by the cylinder head, each one of them has an elastically deformable portion to be elastically deformed by a pressing force of the cylinder head.

4. Valve stem seals - avoid any oil enter into intake, exhaust pipes or the cylinder, also stops leakage of air-fuel mixture from the intake pipe or  the burnt gases from exhaust pipe.

5. Head gasket - Seals coolant and oil, also seals the gas pressure in the cylinders.

6. Pistons - withstands the pressure from combustion, transfer the power onto crankshaft through connecting rod, piston top also a part of the combustion chamber.

7. Piston rings - 
                        Compression rings: Seals the air inside the combustion chamber.

                          Oil rings: Scrapes off excess oil from the cylinder walls.

8. Cam-belt - Connects camshaft and crankshaft to ensure the accuracy of the intake and exhaust timing.

9. Flywheel - Store rotational inertia when engine speed up,and release the rotational inertia when engine, can be used to reduce the speed fluctuation during mechanical operation.

What is the bore and stroke.


Bore - The diameter of the piston and the inside diameter of the cylinder.


Stroke - The distance traveled by the piston from T.D.C(Top Dead Center) to B.D.C(Bottom Dead Center)