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      10-19-2009, 08:07 PM   #1
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Hollowed out secondary cats???

When I had my 2005 Audi S4 I bought a set of downpipes ( had the secondary cat here) and I opened them up with a grinder and broke out all the cat converter element and welded them back together. The cool thing was, It looked 100% stock, fit 100% stock and I got awesome gains when coupled with a nice dual exhaust and ecu flash.

My question is, has anyone tried this with the E9x series cars? I was looking at getting the fabspeed x pipe and secondary cat delete but learned you hafta cut the stock setup to get it on there, which screws you for the visual inspection of any future emissions testing, especially out here in Cali. The cars will still pass the sniffer test without the secondays cats, but they wont pass the vis. test without em. I think ima do the same to this car...

Anyone done this or have any thoughts on this "sleeper" exhaust setup. I would imagine the gains might not be as substantial as if replacing with a new x pipe setup but there should def. be gains there from removing that secondary cat.
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      10-19-2009, 08:10 PM   #2
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Thats Mustang shadetree mechanics right there. Gutting cats for the win.
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      10-19-2009, 08:42 PM   #3
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It's a good idea in Cali since we have to pass visual inspection when we smog our cars.
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      10-19-2009, 08:42 PM   #4
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Quote:
Originally Posted by URBAN LEGEND View Post
Thats Mustang shadetree mechanics right there. Gutting cats for the win.
yessir, old skool stuff, but it works...
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      10-19-2009, 10:01 PM   #5
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I use to have an A6 2.7T back in the day...

It will definitely add power. You may get some resonance, but I doubt it would be a deal breaker.

What is plan b if it sounds like dogshit? ; )
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      10-20-2009, 02:07 AM   #6
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I think I am gonna carefully open up the secondary cats, remove all that good stuff from inside and find some way to weld a tube inside to bridge the voided area, hopefully that would eliminate the resonance and actually make it a straight section. Then cover it all up again with the shell from the cat. Sneaky seaky... I will keep you guys posted. I may tackle this project this weekend.
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      10-20-2009, 02:08 AM   #7
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Quote:
Originally Posted by Singletrack View Post
I use to have an A6 2.7T back in the day...

It will definitely add power. You may get some resonance, but I doubt it would be a deal breaker.

What is plan b if it sounds like dogshit? ; )
Plan B, haha at this point, no plan B, hopefully it sounds good...
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      10-20-2009, 10:34 AM   #8
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Quote:
Originally Posted by SOCAL View Post
I think I am gonna carefully open up the secondary cats, remove all that good stuff from inside and find some way to weld a tube inside to bridge the voided area, hopefully that would eliminate the resonance and actually make it a straight section. Then cover it all up again with the shell from the cat. Sneaky seaky... I will keep you guys posted. I may tackle this project this weekend.
Good idea!
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      10-20-2009, 12:09 PM   #9
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post a writeup with pics for us..
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      10-20-2009, 12:11 PM   #10
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post a writeup with pics for us..
Will do!
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