Advance engine simulation models are an essential tool to accurately characterize the processes that take part inside the engine. They are also vital to evaluate precisely the pollutant compounds formation and to orientate the experimental tests. Therefore, the development of engine simulation and calculation software has been given priority. Then, the group has a spark-ignition and compression-ignition engine simulator based on a thermodynamic multi-zone cuasi-unidimensional model that facilitates the knowledge of the main engine working and operational features. On the other hand, a Stirling engine simulator has also been developed based on a third order model.