Computerized simulation and modeling is for the moment an integrated part of the design process. But the last one is an essential sequence in developing of a qualitative product. In research, as a consequence of CAE programs development, and CAD in particular, had been achieved the development, simulation and evaluation of the products in virtual environment. The present paper shows the simulation option in the AVL BOOST application (available in the specialized laboratories of Automotive and Transportations Department from Technical University of Cluj-Napoca) an single cylinder compression ignition engine model supplied with biofuels in order to determine the variation of heat release during the combustion process and of corresponding losses. The results shown in the paper outline the influences that may appear due to the modification of fuel type and implicitly the properties and operative specifications of the fuel upon injection and combustion processes – those which affect directly the performance and pollution level of an engine.