Originally Posted by cbdallas
Pro Charger: SORT OF like a belt-driven turbocharger, but it's really a different kind of supercharger. It's added on to the front of the engine and uses power from the engine (via belt) to turn a centrifugal 'pump' to force air into the engine.
A Procharger is basically belt driven turbo like he said.. its a centrifugal supercharger as opposed to the ones that bolt on to the intake are roots style super chargers (the ones that whine and sound awesome).
Vortec is another company that makes the centrifugal superchargers.
Only 3 Supercharger kits I know of for the focus are Jackson Racing, Powerworks (no longer makes anything new), and procharger.
Not sure if they are as much work to install but still require a good amount of mechanical knowledge