For the centri blower guys..
 

There is a very interesting article in this month's (Aug2007) MM&FF about making a centri blower perform like a turbo.

They setup a wastegate and a boost controller to a blower combo. This allows you to run a smaller pulley on a blower such as a Vortech or Paxton so that you build boost in the lower rpm and then bleed it off in the upper rpm. This also does away with pulley swaps to "race trim" at the track. One pulley all the time and one knob in the passenger compartment to control boost.

Pick up the mag and read the article. It is interesting.

Sounds like a good idea. Wonder how much it would help out with the tq on those blowers

I've seen something like this years back. I'm looking for the info now, but I believe someone was using a D-1 and a electronic wastegate to do "boost stepping" for the same effect.

Interesting

Sounds interesting, but it seems that it would make the motor very inefficient when bleeding off the boost. The problem I see is that even though you're at lower boost by releasing some of the pressure, you're still generating high-boost heat by spinning the blower at the high boost speeds.

Maybe I'm mistaken.

I guess my next question would be, why not just go with a turbo?

Many of the compressor wheels actually make boost between inducer and exducer, so...yes, the heat may very well still be there. And a problem with blowing off the boost is you have to recirculate it within the confines of your air-metering system.

And alot of the drag associated with the centrifugal blowers is in the gear-train and bearings...they overdrive the compressor wheel by up to 10:1 over the crank RPM (I would suspect in this application, maybe more). That is alot of power required, to overcome the bearing loads on the belt, the gear friction, and the boost generated at the wheel.

Packaging constraints? Take my car for example.

Blow-thru system?

Not if you blow it off before the metering system.

Intercoolers do away with the heat.

It's still a waste of energy. Takes alot of work to spin it up fast, only to release it...sounds like a full-blown lesson in inefficiency. Pun intended!

You guys need to read the article..

we are not talking about overspinning the blower. We are talking about spinning at its efficient rpm which usually is a good bit higher boost than most people would want on the street or on the engines.

Take my old D-1 as an example. I had it pullied for 14psi but it actually was most efficient at a much higher impeller rpm than what I was spinning it at.