The reliability, efficiency and ecological parameters of diesels are mainly determined by their operational perfomance in unstable conditions when the air supply to cylinders lags as compared to the fuel supply. Hereat, the excess air coefficient decreases, which results in decreasing the fuel consumption efficiency as well as the exhaust gas smoke. The aforesaidnecessitates the adjustment of the fuel feed depending upon the amount of the air supplied into cylinders.The modelling of the diesel controller system for the rotation frequency regarding the adjustment of the fuel feed depending upon the supercharging pressure is considered. The mathematical model of the diesel is based on calculating the gas - dynamic processes in each cycle of the cylinder operation, which makes it possibleto take into account the nonlinear characteristics of the diesel in different operational conditions as well as the discreteness of the fuel injection. The digital model enables to obtain the characteristics of the air consumption values in the function of supercharging pressure at various rotation frequencies. Two types of controllers were studied on the basis of the digital model, namely, the ideal one (with the fast - acting valve) and the controller with the measuring element in the form of the fuel pump with the electromagnet drive. The operation of the controllers mentioned was studied both with the adjustment of the fuel feed depending upon the supercharging pressure and without it. For both cases the static and dynamic characteristics of the diesel are obtained. The recomendations for determining the parameters of fuel feed adjustment system are given.