Exhaust flange - Engineering Design Challenge for you Audifans tinkerers

Jim Dupree jdupree914 at sbcglobal.net
Thu Aug 17 15:31:58 EDT 2006

I had a similar problem with one of my 4kq's. The
connection to the outlet of the cat was a flared pipe
with a loose flange and a beveled 'donut' sealing
ring. I don't recall if it was a 3 hole flange or a 4
hole flange. With wear/age/poor fabrication the flared
end pulled thru the flange. i forced it back on the
pipe and tightened everything and it lasted a week or
2. I found a short chunk (4 inches) of exhaust pipe
the same diameter and used a press and a wheel bearing
press flange and created a flare on one end of this
chunk of pipe. The flare I created was larger that the
flare on the original pipe. This was a bit tricky and
an exhaust shop should be able to do this with the
proper tools but I had time and tools to play with.
I force the flange back on to the exhaust pipe like it
was originally and then I took my newly flare pipe and
split it down on side with a disc cut off tool. I then
spread/expanded this pipe enough to force it over the
end of the original flared exhaust pipe and then used
large hose clamps to temporarily compress it around
the original pipe. I slide it in place, tight against
the original flare and welded it on. I had to fill in
the split with the welder (a little tricky) where it
would seat against the seal ring and then grind it to
create a good surface. Since the new flare was larger
that the original the flange could no longer work it's
way out and this allowed enough force to be applied be
the flange to seal the old and new flare to the
sealing ring. It took me several hours overall but
cost me no money, nice to have access to a shop and
the scrape barrel.
You might also look into replacing the fangs on both
the pipe and the cat with something like these v-band
clamp/flange sets. These work very nice and make for
quick removal of a muffler (or cat). We used them on
our 914 race car since we swapped out mufflers
depending on the sound limits of the track we were
running at.
I have a couple of SS 4 bolt flanges at home but I
don't recall the size and I don't really think they
have a taper cut in them. I'll dig them out this
Good Luck

--- SJ <syljay at optonline.net> wrote:

> I have a problem.
> My 88 5kq, non turbo needs a 4 hole mounting flange
> on the end of the
> downpipe for connecting the downpipe to the Cat. The
> flange needs an inside
> bevel to match the flared donut that sits between
> flange and cat.
> No FLAPS has this type of flange. The local Meineke
> shop had nothing to
> match.
> A 4 hole flange in stainless would be nice, but I'll
> settle for anything
> right now.
> I need to come up with a solution and you all can
> help out.
> A summary of the problem, and issues, pix and
> sketches of some ideas that I
> had are posted at:
> www.geocities.com/Audi listers
> If you would like to contribute your ideas via
> sketches, you can upload your
> sketch or pix or text to the site.
> To save you time, you can download my bmp files
> (MSPaint), edit them, anime
> them, and upload them.
> I assume most will know how to edit a Geocities web
> site. If not, you can
> send me your sketches or ideas and I'll add them to
> the site as a linked
> page under your name or your initials.
> To edit/add your stuff to this web site:
> http://geocities.yahoo.com/
> sign in as: XXXXaudilistersXXX
> password: XXXXiloveaudisXXXX
> remove the X's from above info
> SJ
> 85 Dodge PU, D-250, 318, auto
> 85 Audi 4k - - sold but still on the road
> 88 Audi 5kq
> 90 Audi 100q
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> quattro at audifans.com
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