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Ian Dewhirst wrote:
Tracy wrote "It could be argued that the exhaust energy was free anyway so
it doesn’t matter. I don't have enough real world data to back it up but
I don't think this is true."
Back pressure rises with turbine load so you are quite right Tracy, the
energy is not free. I think what the point was about "free" energy is that you are using the exhaust gas, which is actually dumping up to 50% of the energy generated by fuel burn "overboard". It takes about 20-30 HP (rough round numbers from a PL graph) to compress the air needed for boost. The turbo uses the "waste" exhaust gas to do this. The supercharger uses direct mechanical energy to do so.
Obviously nothing is free, but from a net standpoint, the turbo is more energy efficient than is a mechanical drive supercharger.
Dave
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