How to calculate ratio?? Stupid question

[Hounddog]

I've seen many tech articles referring to gear ratio for superchargers when trying to explain/calculate amount of boost produced. How is this calculated? Ratio of crank (drive) pulley size to size of blower pulley??? When I do mine 2.95 upper to 7.0 lower it comes out to 1:4.2 which seems high...when most articles refer to ratios in the 1:3.5 range or less.
Wayne

[MeJay Racing]

Originally posted by Hounddog
I've seen many tech articles referring to gear ratio for superchargers when trying to explain/calculate amount of boost produced. How is this calculated? Ratio of crank (drive) pulley size to size of blower pulley??? When I do mine 2.95 upper to 7.0 lower it comes out to 1:4.2 which seems high...when most articles refer to ratios in the 1:3.5 range or less.
Wayne

The magazines are talking about the internal gear ratio of the blower. For a V-1 s-trim it is 3.45:1. That is used when calculating max impeller speeds.

Here is a good link:
http://www.vortechsuperchargers.com/...rformance.html

Hope this helps.
Mike

[Hounddog]

Originally posted by MeJay Racing
The magazines are talking about the internal gear ratio of the blower. For a V-1 s-trim it is 3.45:1. That is used when calculating max impeller speeds.

Here is a good link:
http://www.vortechsuperchargers.com/...rformance.html

Hope this helps.
Mike

Mike,
thanks, that makes a whole lot more sense....Now I understand the formulas better.
Wayne