4 stroke engines is the engine which completes its cycle in four strokes of piston.

Main parts of the engine
·        Cylinder                                            
·        Piston
·        Piston ring
·        Connecting rod
·        Crank shaft
·        Valves
·        Ignition system
·        Intake fuel system
·        Exhaust gas
·        Cooling system
·        Lubrication system
·        Camshaft system
Piston is used to compress the fuel and transfer power generally by engine to crank shaft.
Spark plug
The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.

The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.
Piston rings
Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:
  • They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.  
  • They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.
Piston Rings
Most cars that "burn oil" and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly. 

Connecting rod
The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

The crankshaft turns the pistons up and down motion into circular motion just like a crank on a jack-in-the-box does.

The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).

Intake fuel system                                                                                                                                      Carburettor in fuel engines is responsible to mix the specific quantity of air and fuel ( air fuel ratio)
In case of diesel engine air inlet system is present.

Exhaust system                                                                                                                     
 In modern engines, to increase the volumetric efficiency, turbo chargers and super chargers are installed.

A turbocharger, or turbo, is a gas compressor used for forced-induction of an internal combustion engine.
Super Charger
A supercharger can be powered mechanically by a belt, gear, shaft, or chain connected to the engine's crankshaft. It can also be powered by an exhaust gas turbine. A turbine-driven supercharger is known as a turbosupercharger or turbocharger. The term supercharging refers to any pump that forces air into an engine, but, in common usage, it refers to pumps that are driven directly by the engine, as opposed to turbochargers that are driven by the pressure of the exhaust gases.

Cooling system
Smaller engines are normally air cooled engines.Larger engines are water cooled, water jacket surrounding the cylinder.

Lubrication system                                                                                                                          
 To reduce wear and tear of the engine.

Ignition system.                                                                                                               
Spark plug, Nozzle in diesel.

4-Stroke Cycle Illustrated


Share your views or discuss.