Method of controlling a turbocharger

A method comprising:

• providing a system comprising a combustion engine and an air intake side, an exhaust side, a turbocharger comprising a turbine and a compressor, and at least a first exhaust gas recirculation line extending between the air intake side and the exhaust side;
• determining the volume of intake gas required to operate the combustion engine at a power level demanded by an operator of a vehicle;
• controlling the operation of the turbocharger to adjust the speed of the turbine to an adjusted speed and wherein the adjust speed is at least one of:
• a speed that results in a change in efficiency of the turbocharger turbine with respect to the efficiency of the turbocharger turbine at the first speed that is an improvement in efficiency within a target percentage range for the turbocharger turbine;
• a speed within a range of acceptable speeds, wherein each acceptable speed has an associated acceptable resonance mode or bending mode;
• a speed sufficient to produce air from the compressor in an amount in excess of the volume of intake gas desired to operate the combustion engine at the power level demanded by the operator of the vehicle;
• determining if the adjusted speed of the turbine produces an amount of air from the turbocharger compressor that is in excess of the volume of intake gas required to operate the combustion engine at the power level demanded by the operator of the vehicle, and delivering any excess air produced by the compressor to another component of the vehicle.