A power unit for an automotive vehicle includes an internal combustion engine, an electric machine electrically connected to electrical power storage arrangement, and a turbocharger comprising a first turbine located in an exhaust line of the engine. This power unit further includes a second turbine, located in an exhaust line of the engine and drivingly connected to the electric machine, and a transmission set. A first input/output of the transmission set is connected to the second turbine and a second input/output of the transmission set is connected to a crankshaft of the internal combustion engine. The transmission set has an adjustable speed reduction ratio between its first and second inputs/outputs.