The experts will correct me, Trevor, if [and I probably am] wrong, but I think that,while both perform a similar function, the turbocharger uses exhaust gases to push air into the engine, and the supercharger is a mechanical unit that does the same but with more power. The Merlin engine used on the Spitfire and Lancaster were supercharged, but I think that turbochargers were used more in diesel engines. Regards, Peter.