[Shotimes] Power adder discussion

[Ron Nottingham]

Centrifigal s/c's are linear, as they are driven directly from the
crankshaft, so the speed of the s/c impeller is directly proportional to the
speed of the engine.  For example, if your pullys are 1:1, and the engine is
turning 5000 rpm, the s/c impeller is also turning 5000 rpm (unless the s/c
has a gear drive which ups the ratio).  Say you change the ratio to 1:2,
where the engine is turning 5000 rpm, the s/c would be turning 10,000 rpm.

Positive displacement superchargers are blowers and do not compress the
intake air directly (turbos and centrifigal s/c's compress the intake air).
Rather, they pack air into intake, and in the intake is where the
compression takes place.  A really great primer on Roots blowers,
centrifigal s/c's, and turbos is in the August issue of Hot Rod.

Ron N. - Dalton, GA
90 SHO
89 325i
88 325
"It takes a man to suffer ignorance and smile"
Think your car is FAST?
Find out at http://www.streetcarforums.com/

Message: 6
From: "bjshov8" <bjshov8@comcast.net>
To: "SHOtimes" <shotimes@autox.team.net>
Subject: Re: [Shotimes] Power adder discussion
Date: Thu, 2 Oct 2003 21:22:11 -0500

I've always thought that centrifugal superchargers were the wrong way to
produce boost, since they are not linear and by operating at high rpm's they
probably have a lot of friction losses.

But what about a positive displacement supercharger?  How does it compare to
a turbocharger at the same boost pressure?

> OK, folks...  To dispell a couple of myths about turbochargers...
>
> First, turbochargers, when properly sized (this email will assume proper
> sizing), WILL produce more torque at a lower rpm than any centrifigal
> supercharger.