4000 Quattro Exhaust/Cat. Help! Help needed!

[chris franz]

I gutted the cat on my 86 4000 after installing a higher flowing mid and 
rear muffler and didn't get any loss or gain in performance.    So I 
wouldn't recomend it.    Atleast from my experience.
~chris
86 4kcsq


>From: Huw Powell <audi at mediaone.net>
>Reply-To: one at humanspeakers.com
>To: "Brian O'Neill" <briano_72 at yahoo.com>
>CC: Joshua Van Tol <josh at spiny.com>, quattro list <quattro at audifans.com>
>Subject: Re: 4000 Quattro Exhaust/Cat. Help!  Help needed!
>Date: Wed, 04 Jul 2001 14:45:27 -0400
>
>
> > > >why dont you just gut it ?? you will get a kinda
> > > tinny
> > > >sound but it doesnt sound like you care. take it
> > > off,
> > > >get a big crow bar and just start jamming it in
> > > there.
> > > >                                       brian o'
> > >
> > >
> > > Besides being illegal and inconsiderate, gutting a
> > > cat can reduce
> > > power because  having a resonant chamber there in
> > > the exhaust may
> > > cause higher back pressure. It can also cause some
> > > weird noises in
> > > the exhaust system.
> > > --
> > > Joshua Van Tol -- josh at spiny.com
> >
> > it is illegal not to have a cat, not to have a hollow
> > one !! do you really think the backpressure would be
> > higher after removing the guts that have at least 100k
> > of crap blown through them ????
> >                                  brian o'
> >
>
>huh?  it's a federal crime (here in the US) to "tamper" wiht emissions
>control equipment.
>
>also, the back pressure issue is not as simple as you think.  Resonances
>can interfere with the free flow of exhaust gasses, reflected pulses can
>create pressure at the exhaust valve of a cylinder right when it opens,
>etc. etc.  The tough part with altering an exhaust system is that the
>(typically) three restrictive elements in our stock systems were
>designed to work together to reduce emissions, noise, and still be
>reasonably efficient.  Not saying they can't be improved upon,
>especially if you take a creative (or destructive) approach to emissions
>controls, but it's not simple and easy.
>
>--
>Huw Powell
>
>http://www.humanspeakers.com/audi/
>
>http://www.humanthoughts.org/

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