In this thesis, internal combustion engines are processed, with emphasis on diesel engine's. In the introduction are stated the most common problems with which manufacturers on the modern market are facing, and the most important years in the automobile industry are briefly presented. After that, some of the engines working parameters and the way how those can change during the working time of the engine to increase total usability are described. Stated are some of the newer technologies used in the engines to keep previously mentioned working parameters within the op-timal borders depending on working regime. The experimental setting is shown in detail, and influence of the electronics in modern diesel engines is indicated. After that, listed are some of the most important sensors used for managing the overall work of the operating assembly, in a way that the information about the current state of the individual subsystems are sent to the central computer, and that central computer is processing them. Based on modern electronically operated engine which is part of the experimental setting, a model in the program for analyzing operating system is made. Before modeling said engine, listed are some of the available models for defining release of the heat introduced by fuel, and for each model theoretical background is presented. The results obtained after starting simulation are con-firmed with the measuring (data available from the manufacturer). In order to improve output cha-racteristics of the real engine, optimization in the special optimization module is made. The goal of the optimization was to increase power and efficiency in a certain range of speed. Optimization results are shown and compared on different graphs, and individual output values obtained after that are more than satisfying. Results are connected with theoretical setup, and alongside that, so-me thesis about Miller and Atkins cycles are confirmed.