Construction:

•         A piston reciprocates inside the cylinder 

•         The piston is connected to the crankshaft by means of a connecting rod and crank. 

•           The inlet and exhaust valves are mounted on the cylinder head. 

•         A fuel injector is provided on the cylinder head 

•         The fuel used is diesel.

(a) Suction Stroke (First Stroke of the piston)

•         Piston moves from TDC to BDC 

•         Inlet valve is opened and the exhaust valve is closed. 

•         The pressure inside the cylinder is reduced below the atmospheric pressure. 

•         Fresh air from the atmosphere is sucked into the engine cylinder through air cleaner and inlet valve.

(b)   Compression stroke (Second stroke of the piston)

•         Piston moves from BDC to TDC 

•         Both inlet and exhaust valves are closed. 

•         The air is drawn during suction stroke is compressed to a high pressure and temperature

(c)   Working or power or expansion stroke (Third stroke of the piston)

•         The burning gases (products of combustion) expand rapidly. 

•         The burning gases push the piston move downward from TDC to BDC 

•         This movement of piston is converted into rotary motion of the crank shaft through connecting rod.

•         Both inlet and exhaust valves are closed.

(d) Exhaust Stroke (Fourth stroke of the piston)

•         Piston moves from BDC to TDC 

•         Exhaust valve is opened the inlet valve is closed. 

•         The burnt gases are forced out to the atmosphere through the exhaust valve. (some of the burnt gases stay in the clearance volume of the cylinder)

•         The exhaust valve closes shortly after TDC 

•         The inlet valve opens slightly before TDC and the cylinder is ready to receive fresh air to start a new cycle.