The thesis work has been developed in collaboration with the company “Leonardo Engineers for integration S.R.L.”, it is part of an innovative and totally brand-new hybrid electric powertrain design. The project is included in a series of works previously carried out by other students, in collaboration with the company, aimed to design and optimize the internal combustion engine that will be exploited as a range extender unit for the series hybrid electric vehicle. General design goal is the minimization of fuel consumption without penalizing the engine power output; other two important aspects that lead the project are the cost involved in the internal combustion engine manufacturing and the noise and vibration produced.