Exhausting question

Shayne thequattroking at yahoo.com
Fri Aug 16 14:51:41 EDT 2002


Politics aside, I can comment on the effectiveness of the exhaust system
relative to change.  I had the exhaust system on the 20V done.  Not because
I wanted to, but because it was rusted out.

At one time, I would have ripped every emission control off the car and not
given a shit.  Now, I guess I fee the "loss" of performance is worth
preserving the environment.

Here is what I did:  First exhaust system included the stock cats and stock
pipe size front to rear.  I eliminated the center resonator because it was
rusted.  Put in a dynomax ultraflow rear can.  I seemed to develop boost 300
rpm sooner.  However, that could have been because the flow characteristics
were better due to the lack of rust slowing down the exhaust.  And Mr.
Bernoulli's law was maximized.  The car was annoying to ride in at speed so
a resonator went back in.  No change in performance.

A short time later a young relative in my family takes the car off-roading
at 110 MPH.  Crushes both cats and basically the exhaust system.  So, now a
COMPLETE exhaust system is done.  WOW, what a difference.  The cats were
MORE then ready to be replace.  Car spooled up SO much quicker.  Got to 1.8
bar VERY fast.  Pipe size used was stock.

Now, on enlarging pipe size, I can say it did make a difference on the V8q.
The car gets 1 mpg better and it pulls so much cleaner in the higher RPMs.
I went up to dual 2.5 inch system.  Prior to this, I took the cats off.
Made no real diff in the performance.  So, I put them back on.

Another audi owner friend of my, took the cats off his turbo 4k and is turbo
5k.  I drove both before and after.  Cars did spook up a bit quicker, but
IMO not enough to warrant killing our air.

So, I hope some of this helps.  I am not telling you to leave the cats on or
off.  I am not without fault:  I have a tow rig that I took them off of
because it tows 5 times better without any of the emission controls on and
gets 20% better economy.  What I am saying is you need to decide what change
you feel comfortable with.  Do them and enjoy them.

If I were doing the 20vt again, I would up the pipe size to dual 2.5" and
leave the cats and resonator on.  When you do the exhaust system, check the
cats with a microscope and see if they are plugged or melted at all.  That
can make a HUGE difference in performance on a turbo car.


Shayne P.

Oakland, CA.

Enough Audis to give plenty of headaches.

Parting:  1972 Mercedes Benz 280 SE 4.5

> From: "Ben Gibby" <jordad at hotmail.com>
> Date: Fri, 16 Aug 2002 18:06:40 +0000
> To: 200q20v at audifans.com
> Subject: RE:Exhausting question
> Keith
> I appreciate the support, I have access to all the equipment to do the work
> myself and the materials will cost about $30 or $40. I figure I might as
> well start somewhere on the road to the car I want and since the exhaust is
> all but shot, why not start there?
> Steve,
> The to do list is-Replace the exhaust system, Replace the ECU, replace the
> injectors and replace the wastegate spring, you see, all related. I lucked
> out and got a car with very few problems and the ones that do crop up are no
> problem. BTW I am a full time mechanic and have access to all the cool toys
> needed to do it all myself.
> Bernie and Phil,
> Um, OK. I can see why only a few regulars regularly post on the list. Most
> are chased off by listers with an attitude.
> Not being chased off,
> Ben
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