homemade supercrager wonder it works like it looks, i know sometime a go there was a post on here where a guy made his own same type thing with the turbo housing but used a electric wheel chair gear, as part of it... im sure you old timers remember

 

it doesn't look like they're overdriving the compressor very much...you have to run turbos at extremely high rpms to compress much air. even if that thing runs twice the crank rpm, your still only turning it at 12k rpms on a 6k rpm motor. that's not going to compress very much air.

 

Especially considering most "modern technology" turbos as he states he uses in his auction frequently spin up near 100,000 rpm...