Archangel007 wrote:
KLAS,
Sprintex, Whipple and Autorotor (et al) are claiming efficiencies of around 70% now with their twin-screw, positive displacement superchargers. They are also claiming rotor speeds in the order of 18,000rpm. This means physically smaller blowers for the same amount of cfm pumped. This speed would equate to roughly 35psi for the Supercharger, with inlet temps well down on the roots type blowers (like 1/2!)
Trying doing that with a turbo supercharger and you would need something the size of a GT70 with plenty of lag, not thanks! Gimme an engine that produces torque from idle, max torque at 2000rpm, and billiard-table flat right through to redline.
I for one would fit a supercharger over a turbo if I was doing one again .......hang on, I am!!! Less complicated, more flexible in the delivery and more reliable.
My $0.02
yes, i know. the modern Lysholm concept is getting better, but the turbos are, too. superchargers have lag, too. it's the way they try to resist changing thier speed. thats why they try to get the rotors as light as possible
my €0.02, there is no better system, both have advantages and disadvantages. you pick what you like or need. if you whant power from idle you go supercharged, you want power from the middle to redline go turbocharged. it works somehow like this.
oh, you want both? use both
The whole design of the impeller is completely different because of the lower rpm.
because they're full of crap as it goes against the laws of physics! But like a supercharger, when the turbo hits boost it makes more power than the it takes. But until it does, you feel the power loss through 'lag', simple right? 
Last time I heard, they hadn't figured out perpetual motion 
