Compound forced induction.

[steve-V8s]

Does a turbo charger generate a pressure differential or does it shift a particular volume of air ? To put my question another way if the input air supply is already above atmospheric is the output boosted or will it still shift the same amount of air ?

I was wondering about mildly supercharging and intercooling the supply to an already turbo charged small engine. The intention would not to be to massively increase the boost but to negate losses due to induction piping and supply cooler air. To ensure the turbo never starves the pressure should, I would think always be above atmospheric, how would it cope ?

[steve-V8s]

DVandrews said:

A friend runs a compound charged engine in his sprint/hillclimb Elise. The supercharger runs directly until around 2500 at which point it is switched via a gate to just run the turbocharger.

Dave

Is that the green one which resides in Abbingdon ?



Can I present my question differentially and for the time being remove the engine from the picture.

Imagine I have a centrifugal compressor running at a fixed speed blowing air down a pipe which is open to atmosphere at both ends and I measure the flow. If I now feed the compressor with air at above atmosphere will the amount of air shifted increase or will it remain the same because the compressor moves a fixed amount of air for a given speed ? Compressor charts refer to pressure ratio which suggests it would increase.

A crude experiment with two cooling fans suggests the flow is increased provided the first fan moves more air than the second, if the two fans are equal there is no effect.