A system comprising: a dual volute turbocharger for receiving exhaust gas from an internal combustion engine and for delivering compressed air to the internal combustion engine, said dual volute turbocharger comprising, a turbine housing comprising, an interior surface defining, a turbine housing interior adapted to receive a turbine wheel, a first volute adapted for fluid communication with the internal combustion engine and said turbine housing interior for delivering exhaust gas from the internal combustion engine to said turbine housing interior, a second volute adapted for fluid communication with the internal combustion engine and said turbine housing interior for delivering exhaust gas from the internal combustion engine to said turbine housing interior, and a turbine housing outlet in fluid communication with said turbine housing interior for discharging exhaust gas from said turbine housing interior, a wall separating said first volute from said second volute, and a valve seat, and at least one valve member engageable with at least one of said wall and said valve seat of said turbine housing for controlling exhaust gas flow from said first and second volutes (54, 56) to said turbine housing interior, with said at least one valve member and said wall of said turbine housing collectively defining a first cross-sectional flow area and said at least one valve member and said valve seat of said turbine housing collectively defining a second cross-sectional flow area; and a controller adapted to control the at least one valve member characterized in that the controller is adapted to control the at least one valve member to have an area ratio constant (C AR) operating range according to a brake-specific fuel consumption (BSFC) of the internal combustion engine, with the C AR defined by the equation: C AR = first cross-sectional flow area / (ρ power * second cross-sectional flow area), where ρ power is the power density of the internal combustion engine in kW/L; wherein when the first cross-sectional flow area and/or the second cross-sectional flow area are less than 0.1mm 2 the C AR is effectively zero; wherein said controller is adapted to control the at least one valve member to have a C AR operating range from greater than or equal to 0.0000 L/kW to less than or equal to 0.150 L/kW. a dual volute turbocharger for receiving exhaust gas from an internal combustion engine and for delivering compressed air to the internal combustion engine, said dual volute turbocharger comprising, a turbine housing comprising, an interior surface defining, a turbine housing interior adapted to receive a turbine wheel, a first volute adapted for fluid communication with the internal combustion engine and said turbine housing interior for delivering exhaust gas from the internal combustion engine to said turbine housing interior, a second volute adapted for fluid communication with the internal combustion engine and said turbine housing interior for delivering exhaust gas from the internal combustion engine to said turbine housing interior, and a turbine housing outlet in fluid communication with said turbine housing interior for discharging exhaust gas from said turbine housing interior, a wall separating said first volute from said second volute, and a valve seat, and at least one valve member engageable with at least one of said wall and said valve seat of said turbine housing for controlling exhaust gas flow from said first and second volutes (54, 56) to said turbine housing interior, with said at least one valve member and said wall of said turbine housing collectively defining a first cross-sectional flow area and said at least one valve member and said valve seat of said turbine housing collectively defining a second cross-sectional flow area; and a controller adapted to control the at least one valve member characterized in that the controller is adapted to control the at least one valve member to have an area ratio constant (C AR) operating range according to a brake-specific fuel consumption (BSFC) of the internal combustion engine, with the C AR defined by the equation: C AR = first cross-sectional flow area / (ρ power * second cross-sectional flow area), where ρ power is the power density of the internal combustion engine in kW/L; wherein when the first cross-sectional flow area and/or the second cross-sectional flow area are less than 0.1mm 2 the C AR is effectively zero; wherein said controller is adapted to control the at least one valve member to have a C AR operating range from greater than or equal to 0.0000 L/kW to less than or equal to 0.150 L/kW. C AR = first cross-sectional flow area / (ρ power * second cross-sectional flow area), where ρ power is the power density of the internal combustion engine in kW/L; wherein when the first cross-sectional flow area and/or the second cross-sectional flow area are less than 0.1mm 2 the C AR is effectively zero; wherein said controller is adapted to control the at least one valve member to have a C AR operating range from greater than or equal to 0.0000 L/kW to less than or equal to 0.150 L/kW.