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RE: Rattlin' CAT

I seem to recall a formula from about 20 years ago for calculating the 
neccessary carb size for a performance vehicle. It was cu.in. x max rpm /3456. 
This would give an approximate air flow volume in CFM. Example: Chevy 350 
turning 6000 rpm - 350 * 6000 /3456 = ~607 CFM so a Holly 650 would provide 
enough capacity for the setup. You can do the math for a mustang 5.0l vs a the 
Audi 2.3l. Of course this is for a normally aspirated engine - suspect you 
just need to factor atmospheric pressure (boost) into the equation. 


From: 	owner-quattro@coimbra.ans.net on behalf of AUDIDUDI@delphi.com
Sent: 	Friday, August 30, 1996 6:19 AM
To: 	rjandrew@post.cis.smu.edu; QUATTRO@coimbra.ans.net
Subject: 	Re: Rattlin' CAT

> > You mention that it "WILL" pass emissions.
> > 
> > Are you sure?

Not here in Arizona ... they now attach a piece of litmus paper to the tail
pipe and if it doesn't indicate the right ph factor -- meaning the cat's in
place and functional -- you fail, regardless of whether you pass the visual
inspection or not.  At the moment, I don't know of any way to beat this nor
do the handful of my friends who were forced to buy cats for their Mustangs
and Camaros over the past year ... pretty damn sneaky, if you ask me!

With all of the high-performance cats now on the market, has anyone found a
reasonably priced replacement that won't strangle flow?  When my 200q comes
home from the paint shop, the next step for it is a new exhaust and I would
like to run a cat if possible ... inspections are every other year so I had
been thinking that I could get away with running a straight pipe in between
but I now find both of my routes to work are frequently monitored by mobile
emission-testing vans: If your car fails as it drives by, a ticket's mailed
to the registered owner!  They usually put them in places where the traffic
flow naturally narrows to one lane (on-ramps, etc.) and by the time you see
one, there's no way to turn around or avoid it (if you doubt this, just ask
my friend who swapped cars with me for two days -- he wanted to try my 200q
and I wanted to try his '95 Camaro -- and how was I supposed to know he had
replaced the cats with straight pipes, anyway?).

I haven't checked any numbers but my guess is that a cat designed for a 5.0
Mustang or Camaro will probably flow well enough for a breathed-on 2.3L ...
of course, I could always be wrong, too!  Any comments will be appreciated.

     _             _             
    / l       l o l  \       l o   Jeffrey Goggin
   /__l l l / l l l  l l l / l l   * * * * * * *
  /   l l_l \_l l l__/ l_l \_l l   AudiDudi@delphi.com