A turbocharger system for an internal combustion engine that powers a vehicle having a pressure vessel storing pressurized air, the turbocharger system comprising: a turbocharger including a compressor driven by a turbine, the turbine defining an exhaust gas inlet for receiving exhaust gas from the engine and an exhaust gas outlet through which exhaust gas is discharged, the compressor defining an air inlet for receiving air to be compressed and an air outlet through which compressed air is discharged for delivery to an intake system of the engine; a valve system comprising a single valve defining a first inlet receiving compressed air from the compressor and a second inlet receiving pressurized air from the pressure vessel, the single valve further defining a main outlet through which air is discharged for supply to the intake system of the engine, and a recirculation outlet through which compressed air received at the first inlet is diverted so as not to pass out the main outlet, the single valve being electrically controllable to move between first and second valve conditions in which either the pressurized air from the pressure vessel or the compressed air from the compressor is supplied to the intake system of the engine, respectively, the single valve shutting off the pressure vessel when in the second valve condition; wherein the single valve is further operable, when in the first valve condition, to divert the compressed air from the compressor through the recirculation outlet into a recirculation conduit that leads into the air inlet of the compressor, such that compressed air is recirculated back to the compressor when the air intake system is being supplied by the pressure vessel. a turbocharger including a compressor driven by a turbine, the turbine defining an exhaust gas inlet for receiving exhaust gas from the engine and an exhaust gas outlet through which exhaust gas is discharged, the compressor defining an air inlet for receiving air to be compressed and an air outlet through which compressed air is discharged for delivery to an intake system of the engine; a valve system comprising a single valve defining a first inlet receiving compressed air from the compressor and a second inlet receiving pressurized air from the pressure vessel, the single valve further defining a main outlet through which air is discharged for supply to the intake system of the engine, and a recirculation outlet through which compressed air received at the first inlet is diverted so as not to pass out the main outlet, the single valve being electrically controllable to move between first and second valve conditions in which either the pressurized air from the pressure vessel or the compressed air from the compressor is supplied to the intake system of the engine, respectively, the single valve shutting off the pressure vessel when in the second valve condition; wherein the single valve is further operable, when in the first valve condition, to divert the compressed air from the compressor through the recirculation outlet into a recirculation conduit that leads into the air inlet of the compressor, such that compressed air is recirculated back to the compressor when the air intake system is being supplied by the pressure vessel.