4000 Quattro Exhaust/Cat. Help! Help needed!

[Huw Powell]

> > >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/