Management and diagnostic systems play a significant role in the design of current powertrains, especially taking into account targets in terms of specific fuel consumption and pollutant emissions. Mathematical models are useful tools in this field, with applications that range from the definition of optimised management systems, to Hardware- and Software-in-the-Loop testing (HiL and SiL) and to model-based control strategies. The paper presents a “control-oriented” library developed at the University of Parma for the “real-time” simulation of actual automotive engines and its application within an original HiL system developed by Fiat Research Center/Fiat Powertrain.