polished impeller/volute
 

Is there anything to be gained from polishing the impeller and the inside of the volute on a turbo/ centrifugal supercharger? It is still rough from casting on the inside of the impeller fins and inside the volute... cant imagine thats good for air velocity

Maybe Ion can chime in.

Personally, I think not much of a gain to really make much or noticalbe difference

I think im going to pass... i looked into maybe a polymer coating to smooth out&reduce coefficient of friction... could even probably get it done in the lab at school (im a plastic engineering student) but i would be afraid i would mess up the clearance for the impeller blade with a coating, or make it too big with a polishing.

I almost wonder if the casting helps grab air and move it or