Four Stroke Petrol Engine

Intake stroke
In this stroke, fuel and air is allowed inside the cylinder by the downward movement of the piston which involves the opening of intake valve. Compression stroke
Piston moves upward again in this stroke and the fuel and air mixture is compressed. Power stroke
In this stroke power is generated when the spark plug ignites the fuel and piston moves down, this helps the engine to start initially after which the engine gets power enough to run for another four stroke process and this route endures till the engine is switched off.

Exhaust stroke
In this stroke, piston moves again and the exhaust gases are passed out through the exhaust valve. Parts of Four Stroke Petrol Engine
The four stroke petrol Engine includes following parts:-
1. Piston
A disk or short cylinder fitting closely within a tube in which it moves up and down against a liquid or gas used in an internal combustion engine. It is the main part of Petrol Engine which transforms the energy of the expanding gasses into mechanical energy. The piston rides in the cylinder liner or sleeve. Pistons are commonly made of aluminum or cast iron alloys. 2. Cylinder

Part of the petrol engine which contains piston is known as cylinder it is the part where four processes are done (intake, compression, expansion, exhaust). It also provides protection.

3. Crank Shaft
A Device used to convert linear motion into rotatory motion. It is connected with the flywheel and it transmits energy from engine to flywheel 4. Cam shaft
It is an oval shaped part used to control intake and exhaust valves.

5. Connecting rods
Connecting rod connects the piston with the crank shaft.

6. Crank Case
Crank case is the part where the crank shaft moves, lubricating oil also stays in the crank case.

7. Valves
Valves are devices used to regulate the flow. These include inlet and exhaust valves. Inlet valves allow fuel and air inside the cylinder, while exhaust valves allow exhaust gases to escape the cylinder. 8. Carburetors

Carburetor is a device used to mix air and fuel in the engine with a certain ratio.

9. Crank pin
Pin which joins the connecting rod and crank case

10. Piston Pin
A device which connects the piston with the connecting rod. It is also known as Gudgeon pin 11. Piston Rings
There are two types of piston rings
a) Compression rings do not allow mixture of oil and air to reach the crank case and mix with lubricating oil.

b) Oil rings does not allow the lubricating oil to go to cross the piston. Oil ring is one whereas compression rings are two.

12. Spark Plug
Spark plug provides a spark to ignite the compressed fuel (or the air and fuel mixture) to give the engine a start and start the combustion process.