I found this graph a couple years ago, and found it interesting. Yes, I know there's a turbo in there, but it's a type of supercharger. The various types of superchargers are correctly named below:



Note how closely the Roots blower's torque curve follows boost. Also, the power advantage of the turbo is very clear on this graph, as well as its peaky delivery.

It's shocking to see a turbo yields more low initial torque than a centrifugal blower and also strange to see that the turbo levels off. I figured it would continue on up.. more so than the centrifugal

turbo depends a lot on other factors. Another reason I like belt-driven superchargers - the consistency is hard to beat. The low end torque is where it's at anyway. I prefer a grunty low end motor to a high revving one. More fuel efficient and less rotating speed = less chance of breakage

The engines used in these tests must've been monsters. On the dyno, my car's max wheel torque was about where the centrifugal blower's starts at 2500 RPM!

A lot of people think turbos have superior fuel efficiency compared to roots blowers. Their reasoning might be that turbos are more "efficient" power adders, that blowers suck power from the engine, and that turbos don't use much fuel at cruising speeds. But they don't consider that an efficient power adder doesn't mean a fuel efficient one, blowers require almost no power at cruising RPMs, and they often forget about our boost bypass, which effectively turns the motor from FI into 8.5:1 N/A.

Yeah, I got tired of that pretty fast. PowrTuner to the rescue! Of course, if I ever want to chug, I just put it into cruise and it's back to the old way.

ofcourse with an effective tuning solution...during regualar driving you can have the ecu lean out the mixture to get optimum mileage.

I have never seen exactly how efficient the centrifugal style was on paper...and i always wondered why the mustang guys used them... i guess though you pretty much have the efficiency of a turbo,with superior intercooling vs a regular roots/screw..

quote: "ofcourse with an effective tuning solution...during regualar driving you can have the ecu lean out the mixture to get optimum mileage."

I've never tried this, as I thought the PCM would just compensate. But I have read about some advancing the timing really far to get 45+ mpg.

quote: "i guess though you pretty much have the efficiency of a turbo,with superior intercooling vs a regular roots/screw.."

Centrifugals also sound really cool! Better than Whipple, imo.

quote: "I hoped that using that style housing on the L67 might be possible to utilize air to air intercooling but I see no way to do it"

Believe it or not, it's possible to do air-to-air intercooling on the L67 with the factory blower.

Sweet article on supercharging:

http://www.jagweb.com/aj6eng/supercharging_article.html

Very good read, Andrew! One of the things to keep in mind - the inefficiency of a roots blower has one small advantage: it helps in keeping the torque curve flat. If it were more efficient, like a turbo, you would get more power up top, but the roots design encourages that strong low-end grunt, albeit less horsepower output overall. Twin screw is my personal favorite. Perfect power delivery, imo!

and another article on flow for the m62, basic, but a good read nonetheless:
http://www.aerospaceboy.com/384/analysis.htm

and more:
http://www.corvetteactioncenter.com/specs/c6/2009/zr1/blower.html

and a very helpful pic:
http://www.corvetteactioncenter.com/specs/c6/2009/zr1/images/64266.gif

so what kind of superchargers does our Riviera have factory?

Roots blower, manufactured by Eaton:

http://www.eaton.com/EatonCom/ProductsServices/PerformanceProducts/Products/Superchargers/M90/index.htm

Detail drawing (this is different from the older Gen III used on the Riviera):

http://www.eaton.com/ecm/groups/public/@pub/@eaton/@per/documents/content/ct_167919.jpg