In this paper the cycle of a two-stroke and three-stroke diesel engines is described. The work principle, their application, advantages and disadvantages are discussed in detail. One of the most important points with diesel engines is the fuel injection, which can be either direct or indirect. Comparing the two we can safely conclude that the indirect system is a part of history while the direct fuel injection system has great potential for the future use and development. To start up the diesel engine, besides the fuel injection, we need a Cold Start Device (CDC), injection system regulator and a high pressure pump. In order for the engine to function properly, regulation and injection systems have to be harmonized, otherwise engine damage, toxic fuel emission and motor malfunction may occur. The purpose of the high pressure pumps is the creation of the fuel pressure during its injection into cylinder. There are multiple types of high pressure pumps but their purpose is the same. It is taught that in the future engines with forced induction will be most commonly used. The basic purpose of forced induction the increase in power and revolving momentum which is accomplished by injecting a large amount of air into cylinders. Forced induction is made possible by using a combination of intake manifolds and an external turbocharger. External forced induction is created by using a turbocharger and an engine superplug. In day to day use a turbocharger was shown to be much more reliable than the superplug or supercharger. By combining the two we can mask their individual drawbacks and reach the highest power possible.