Hi Guys,

I live in the Middle East (am orginally from the UK) and it's hard to ship/order exhausts over here so I decided upon a reliable and reputable custom exhaust shop in town...

I installed a custom exhaust onto my Audi TT 00 quatro in July 07.. A simple straight pipe, silencer design... no muffler at the back... The reason for doing this was I originally installed a huge muffler at the backbut it was quieter than the stock exhuast and the tips didn't look good at all !

Also note, - over here in the Middle East, girls aren't really into cars, for example 98% can't drive a manual tranny (!) and aren't into modding cars at all so when your in an exhaust shop, they automatically think your going to want some low sounding, non-high performance exhaust!!- Big mistake for this racing chick haha !

Anyways, after changing this, the exhaust sounded lovely and sporty and made a nice rumbly deep sound... Obviously over time the sound wore in and become much louder... Now around Dec. 07, the car starting sounding like a tractor! Insanely grunty and like the exhaust had a hole... not an attractive sound for the TT at all !

I had obviously kept the originial catalytic converter and took it back to the shop asking them to put this back in, hoping to get rid of this grunty unattractive sound avoiding that awful huge muffler...

Now, the mechanic told me that I will lose a lot of power putting back in the cat but obviously the sound will be reduced, but not so much as putting in a muffler... (He said I could also put two small mufflers at the back of the audi, to reduce the sound but obviously will be much, much quieter than just putting back in the cat)

But, a friend of mine (previously owned a vw) hadtheir turbo blew from installing back his cat in his custom exhaust system - can this happen on my car???!!!

I paid about 1,400 $ for the complete system so obviously don't want to end up spending a lot more...

I have put back the cat and wanted to ask you guys what your opinion is...

Either:

A) Stick with the cat, losing about 7% power... but the main concern is will I encounter problems internally, i.e. with the turbo??
B) Take it back, remove the cat, and install 2 small mufflers at the back costing me another 250 $... but this will signifcally reduce the sound!

Obviously when it comes to whether it will damage the engine/turbo this is my no.1 concern, not the sound of the exhaust..

Thanks guys, thought i'd ask the experts
Any help is much much appreciated !

 

The stock large single cat (opened to 3") only cost 10hp on a 600hp car. I would say thats not restrictive at all. So if thats what your using, keep it. However adding in a resinator would really help the sound and is cheap.

As for your friend, thats what we call a coincidence. A cat wont blow a turbo.

 

^ cheers for the advice cincy..

Im glad that it's coincidence...The stock cathad been sitting in the a/c in my house for around 6 months before being installed back on the car.. not lying around outside or anything..

Il take the resinator option into thought as well..

White smoke was coming out of my exhaust as soon as I put back on the cat and started it up for the first time, this is normal right ?

 

I haven't heard of that happening in normal circumstances...keep an eye on that[&:]

I always wondered what exactly the loss was on the stock cat. According to cincy...it's 1.6%. If you assume an exhaust makes a 20hp gain...that's not even a 1/2 hp loss.

What high flow cats flow about as good as the stock? I want to DIY an exhaust but I don't wanna have to mess with grinding/welding the stock cat into a 3" section. Rather just clamp up a 3" high flow.

 

I'm not sure what everyones obsession is with 3" pipes. The stock diameter flows well, until you're talking about doubling your Hp.

Fun Fact:

Exhaust gasses cool and condense as they travel down the pipe, dense exhaust gasses act as a restriction on their own. Think if it as really fast setting concrete. You pump it in a pipe as a liquid and it starts to set. If you have a large diameter pipe, the velocity is low, and theres more time for it to harden before it leaves the other end. If you use a smaller diameter pipe, velocity is raised, and it exits the pipe before it gets too hard. Of course too small a pipe is restrictive as well, but everyone understands that part already.