[Fasterthanyou]

2 kinds of superchargers, those that are the real deal and those that don't. The real deal are positive displacement like the eaton, roots, whipple, etc. Those can produce boost at any RPM. The hair dryers can't produce boost at low engine speeds because they're blowing air, not the same as compressing. They DO compress the air because of the volume of air that they move at higher RPM. The engine can't accept all the air being flowed by the blower and that builds boost .
"Unique Internal Bypass Valve. The key feature of every Magna Charger system is the unique internal bypass valve. This virtually eliminates the parasitic pumping loss of the supercharger under part throttle and cruise conditions. For example, an Eaton M90 requires less than 1/3hp at 60 mph cruise."
That is why I like the positive displacement blowers like Eaton and Whipple. They are truely more efficient in all conditions than even your centerfugal blowers. I like the hair dryers on the street with v8's because most v8's don't need any more low RPM horsepower... they've got too much as it is so the centerfugal is perfect.
I'd consider a turbo over either of these but if the blower's cheap, that would be reason enough for me to use one . But $3000+ isn't cheap.