Re: Replacing leaky pre-muffler/emissions

[PDQSHIP@aol.com]

In a message dated 96-08-30 14:19:51 EDT, you write:

<< Picking up on the exhaust thread, I have a leaky pre-muffler (ahead of LR 
 wheel) on my '87 5kcst.  The car feels as though it has a clogged cat, low
on 
 power, very sluggish, takes a while to spool up.  Would this leak cause 
 increased back-pressure leading to these symptoms?  
>>  IF you have a clogged cat, which is usually caused by a rich fuel
mixture, the cat will clog first, then once it's done meltdown, it chunks and
will plug the 3 rear mufflers...  Pull the back side of the exh off the cat
and take a look, it should look like honeycombs, if not, more like melting
glue....   The audi cats are 3 chamber types, front honeycombs, dead air
space, rear honeycombs...  So you will need to pull the front side off to see
that section....   If the front is melted and the rear isn't, chances are you
don't have chunks in the mufflers (duh I guess)....  
What is the function of 
 the pre-muffler, other than muffling? 
The 3 mufflers and the cat all address a specific resonance (exhaust sound at
a given engine load/rpm), so removal of any will affect the whisper a stock
system provides....  
  Can I replace with a straight pipe, an
 aftermarket muffler or is it part of a tuned system so it should be replaced

 with the OEM part?  I have a new rear muffler and the rest of the exhaust is

 in good shape so I'm not inclined to replace the whole thing.  

Straight pipe will increase performance slightly, tho that will be off set by
a different exhaust note....   An aftermarket muffler is the last thing you
want on there, it has the potential of increasing backpressue and still
changing exhaust note....  The two fronts are available as a separate part, I
do believe....  OEM lasts about 7-8+years, which is good by any exhaust
standard, and more than justifies the higher price, IMO
 
 In Easton, PA, starting recently, we are exempt from emissions testing based

 on zip code.  I was surprised when even the modified motor in my 911 passed 
 last year without a cat (no cat req'd for '74).  Is there any value on
having 
 the emissions test done anyway to catch a possible problem? 

Won't hurt, tho a dwell meter on the O2 Freq valve test port might prove more
valuable to you ....

HTH

Scott