In two strokes Compression ignition engine a cycle is completed in two stroke of a piston or one complete revolution (360º) of a crankshaft. In this engine the suction stroke and exhaust strokes are eliminated and ports are used instead of valves. The fuel used in this type of engine is diesel.

The major components of a four stroke compression Ignition engine are.

Cylinder: It is a cylindrical vessel in which a piston makes up and down motion.

Piston: It is a cylindrical component making up and down movement in the cylinder.

Combustion Chamber: It is the portion above the cylinder in which the combustion of the Fuel-air mixture takes place.

Inlet and Exhaust ports: The inlet port allows the fresh fuel-air mixture to enter the combustion chamber and the exhaust port discharges the products of combustion.

Crank Shaft: It is a shaft which converts the reciprocating motion of piston into the rotary motion.

Connecting Rod: The connecting rod connects the Piston with the crankshaft.

Cam shaft: The cam shaft controls the opening and closing of inlet and Exhaust valves.

Fuel Injector: It is located at the cylinder head. It is used to admit the fuel into the combustion chamber.

Working: When the piston moves from bottom dead centre to top dead centre, the fresh air enters the crank chamber through the valve. The air enters due to the pressure difference between the crank chamber and outer atmosphere. At the same time the air above the piton is compressed.

            Fuel with the help of fuel injector is admitted into the combustion chamber at the end of stroke. The combustion takes place as the temperature of the fuel-air mixture reaches its ignition point. Due to the explosion of the gases, the piston moves downward. When the piston moves downwards the valve closes and the fresh air inside the crank chamber is compressed. When the piston is at the bottom dead centre, the burnt gases escape from the exhaust port.

At the same time the transfer port is uncovered and the compressed air from the crank chamber enters into the combustion chamber through transfer port. This fresh air is deflected upwards by a hump provided on the top of the piston. This fresh air removes the exhaust gases from the combustion chamber.

            Again the piston moves from bottom dead centre to top dead centre and the air gets compressed when the both the Exhaust port and Transfer ports are covered. The cycle is repeated.