Corky Bell’s Comparison of Superchargers

UPDATED LEXTREME FORUMS - Post Questions Here!

The table below was transferred from Corky Bell’s book Supercharged!  ISBN # 0-8376-0168-1 Page 8

Characteristic Roots Centrifugal Screw
Low Speed boost capability A D A
High boost – Pressure capability (10+ psi) B A A
Fast boost rise A B A
Thermal Efficiency C A A
Volumetric Efficiency B B A
Ease of Intercooling C A C
Power Loss through supercharger C C C
Simplicity of installation B A B
Noise C C C
Vibration B B B
Space Requirement C B C
Installation Convenience C B C
Cost B A C
Score 2.69=B- 3=B 2.77=B-

A= Excellent-4; B=Good-3; C=Fair-2; D=Poor-1

The final score is the total points divided by the total.  I am getting the average of all the scores.

Root Score:  2.69  is B-
A-2 = 8
B-5 = 15
C-6 = 12

Centrifugal: 3.0 is B
A-5 = 20
B-5 = 15
C-2 = 4

Screw: 2.77 is B-
A-5 = 20
B-2 = 6
C-5 = 10

Here is another comparison of supercharger types:

Type Fix Displacement Internal Compression ratio
Roots Yes No
Centrifugal No Yes
Screw Yes Yes

Thermal Efficiencies of typical superchargers

Type Et (%) Temp increase with 1 psi
Roots 55 18.5
Screw 70 14.6
Centrifugal 75 13.6
Turbocharger 75 ???

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