I came across an article online at the American Woodworker website titled "Soup up Your Shop" they suggest replacing the dust collector impeller with a better one.:
4. Better Impeller. Has your shop outgrown your 2-hp collector? Before you buy a 3-hp collector, consider upgrading the impeller on your old machine. An aftermarket impeller from Oneida Air Systems will fit most 2-hp collectors and improves cfm by 30 to 80 percent. In testing,we found the more you load your collector, the greater the benefit. The large fins offer greater surface area to move more air. Plus, these impellers are statically and dynamically balanced so they run truer and help extend the life of your motor.
Continental fan sells an airfiol that looks worth considering.
I'm wondering if anyone has tried an impeller upgrade or has an informed opinion on the subject.
Phil
http://lumberjocks.com/topics/48783
Beware; One consequence of increasing the performance of an undersized impeller would be the increase in power requirement may exceed the ability of an over-rated motor causing it to overheat and fail. My shop vac fan draws cooling air thru the motor as well as thru the filter and maintaining this flow would be a critical factor.
Good practice would be to monitor both motor temperature and motor amps when improving the impeller.
I'm new here, but I just got one of those 14" TEK355 impellers from oneida. I'm pairing it with a 4.5HP two speed pool pump motor I got cheap. I haven't built a housing, but I have tried it and on high speed it moves an absurd amount of air, and it's quiet and balanced.
My original plan had been to put it with a 2-3HP motor and restrict the intake to prevent overloading, but I got a big motor for a better price so I will build my DC full size.