View Full Version : Exhaust pipe between cat/downpipe and "the rest" (flex pipe) WHERE?!

09-04-2018, 06:34 AM

Can I have any suggestions on the exhaust part with the flex pipe? Itīs located between the Cat/testpipe/downpipe and connects to the rest of the exhaust.

Had to cut it and install a new flexpipe, now its leaking and itīs just a mess..

Also I got 034 HFC/downpipe 3" and the rest of the exhaust is aftermarket, 2.5". This is leaking, cut and 2.25"..

Iīd like it 2.5" or larger..

I have searched alot, maybe im searching with the wrong words?? What is it called?



09-04-2018, 07:29 AM
Audi catalog terms are in "quotes". USA industry terms in (parentheses).

- The factory setup is a K03 turbocharger which connects directly to a "catalyst" (catalytic converter).
- The catalyst can optionally be replaced with a "test pipe" when testing for performance problems caused by a clogged catalyst, or illegally for improved performance during road use.
- The catalyst is bolted to the "connecting pipe" (downpipe).
- The connecting pipe is sleeve-fitted to the "middle exhaust muffler" (mid-muffler AKA resonator).
- Finally, the "rear exhaust silencer" (muffler) is fitted at the back.

For a flex pipe, I would recommend only a fully stainless steel piece that has an "interlocking liner" and is specifically rated for turbocharged applications. The good stuff will generally cost 2-5x more than a regular run-of-the-mill flex you'd put on a minivan or whatever. Vibrant TurboFlex is one example of something decent you could use.

If it was recently repaired with a new flex, it certainly should not be leaking. And it certainly should not be "a mess". The flex on a 1.8T can be a little challenging to weld in-place (without removing the downpipe), but should be no problem for an ace welder. It sounds like you need one of those.

Joe Jr.
09-04-2018, 09:42 AM
I have the 3" 034 downpipe with a v-band connection and a piece of 3" flex pipe connected to the vband and then to the exhaust beyond that. I"ll see if i can dig up some pics of how mine is connected. i really like how it worked out. 3" high flow cat to the 034 down pipe to the flex back...

original cat & down pipe next to the hfc & 034 downpipe
https://farm2.staticflickr.com/1866/44424352972_230a181f26_z.jpg (https://flic.kr/p/2aFCqqd)20180408_170716 (https://flic.kr/p/2aFCqqd) by J M (https://www.flickr.com/photos/138012142@N03/), on Flickr

pic from front of car looking back at down pipe to flex connection and pipe beyond.
https://farm2.staticflickr.com/1855/44474126961_0fd3d74654_z.jpg (https://flic.kr/p/2aL2wur)20180515_213948 (https://flic.kr/p/2aL2wur) by J M (https://www.flickr.com/photos/138012142@N03/), on Flickr

oh and by the way, that hfc and 3" down pipe makes the stock k03 sound a lot better. You can hear it spooling.