[55effie]

Wow, there oughta be a section on this forum JUST for 383 questions and topics. I just went through about twelve pages and there must be two threads per page about 383s.

So, After doing a little research I realize that superchargers are an animal all on their own. Is a Twin Screw the same as a Roots SC? And why is the 3 lobe rotor style called "Roots"?

It does not seem like a Roots type blower would have a very low thermal efficiency as some other types.

[techinspector1]

Originally Posted by 55effie

Is a Twin Screw the same as a Roots SC?

Faintly similar in that there are two rotors in each, driven mechanically off the crankshaft.
The twin screw, also known as the Lysholm screw, was concocted some 75 years ago by a Swede named Alf Lysholm. Being more efficient than the Roots-type, most of the large air compressors you see on the street being used on construction (or destruction) jobs are Lysholm screws.
Here is just one of many google entries explaining the blower...
http://www.custom-car.us/superchargers/twin-screw.aspx
The Roots blower was invented by the Roots brothers, Philander and Francis, about 155 years ago. Scroll down here for an interesting storyline....
There are many stories about the first uses of the Roots blower. The one I like best is that it was used to blow fresh air down into mine shafts to keep the miners aspirated.
http://www.dresserroots.com/document...0508_broch.pdf

Originally Posted by 55effie

And why is the 3 lobe rotor style called "Roots"?

You can see by the storyline above that the 3-lobe was introduced in 1914. The original 2-lobe was introduced in 1854.

Originally Posted by 55effie

It does not seem like a Roots type blower would have a very low thermal efficiency as some other types.

There are certainly blowers out there with a higher efficiency. The Roots beats the air unmercifully. I haven't seen an efficiency graph, but would suspect the centrifugal to be the most efficient.

[55effie]

Centrifugal is the most thermal efficient according to that web-page you posted, however it produces the least amount of boost at low RPM. Thus, application seems to necessitate the type of blower one desires. Hard to believe that technology that once supported breathable air for miners is now used for recreation in automobiles.