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Re: Braking the Ceramic Stuff out of my CAT's...

It's something along the lines of the booster effect in carbs. If a fluid
is dumped through a restriction, it will tend to speed up (Vernoulie's
principle). If the exhaust dumps in to a non restrictive area, it will
slow and collect until the next exhaust pulse pushes it further. The fluid
in the restiction will have a momentum and draw more exhaust out with it.
Scavenging. With a slight restriction, you will gain bottom end, but it
will become a major restriction at the upper end when more volume is
required and no scavenging.

When I gutted my cat, I lost noticable bottom end, but gained it back
through faster turbo spooling and higher top end. Supposedly, though the
lower the backpressure, the better with a turbo engine.

*Steve                                       Sachelle Babbar
*'84  5ksT 1.6-2.0 bar                    <SBABBAR@IRIS.NYIT.EDU>
*Cockpit adjustable wastegate, AudiSport badge
*Disclaimer:"Any information contained herein is based purely on my own
*personal experience and may not necessarily reflect yours. Use caution as
*your results may vary from mine."

On Thu, 28 May 1998, Sargent Schutt wrote:

> Regarding this feline surgery: I found in the 90 90 quattro 20v that the car
> actually performed better with the cat in tact. Something with the engine
> being designed to operate with a certain amount of back pressure. It ran much
> smoother and noticeably stronger with the cat than without. 
> Any data/expert explanations of this phenomenom?
> Sarge
> 91 200q still sore in the rear