I think A_Harmann has a pretty good answer here.
Originally Posted by A_Harman
100% of the energy to drive a supercharger comes directly off the crankshaft.
In a turbocharger, part of the drive energy is subtracted from the crank in the form of lost torque due to pumping work pushing the exhaust out against turbine pressure.
But most of the drive energy comes from expanding the exhaust through the turbine, which causes a drop in temperature and pressure of the gases.
In round numbers, about 30% of fuel energy goes out the exhaust. Putting a turbine in the exhaust allows some of that energy to be recovered.
Another advantage that turbochargers have is the centrifugal compressor is more efficient than Roots or Screw compressors. Mechanically driven centrifugal superchargers, such as Vortech or ProChargers have efficiency on a par with a turbo compressor, but they take all of their power from the crankshaft.
Originally Posted by A_Harman
100% of the energy to drive a supercharger comes directly off the crankshaft.
In a turbocharger, part of the drive energy is subtracted from the crank in the form of lost torque due to pumping work pushing the exhaust out against turbine pressure.
But most of the drive energy comes from expanding the exhaust through the turbine, which causes a drop in temperature and pressure of the gases.
In round numbers, about 30% of fuel energy goes out the exhaust. Putting a turbine in the exhaust allows some of that energy to be recovered.
Another advantage that turbochargers have is the centrifugal compressor is more efficient than Roots or Screw compressors. Mechanically driven centrifugal superchargers, such as Vortech or ProChargers have efficiency on a par with a turbo compressor, but they take all of their power from the crankshaft.