It is designed to do a 4 stroke cycle namely: Suction, Compression, Power, Exhaust. Its a diesel engine.
The diesel engine (correctly known as a compression-ignition or CIengine) is an internal combustion engine in which ignition of the fuel that has been injected into the combustion chamber is caused by the high temperature which a gas achieves (i.e. the air) when greatly compressed (adiabatic compression).