the main reason that its not done much is that you need to take drive off the front end of the engine. It might be a possibility in the cossies with the engine orientation, but on the FWD stuff like RST's it would be much more difficult.

In theory a turbo charger is using otherwise wasted energy (thermal recovery from exhaust gas) and so increases thermodynamic efficency. Since a SC takes power directly out the crank its less efficient, but its advantage is that there is no lag.

I'd like to see it done more though.

JAmes.