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Thread: *** what's the best way to gut downpipes on rs6? ***

  1. #1
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    *** what's the best way to gut downpipes on rs6? ***

    I currently have my car in getting some work done and have the ability to remove the downpipes and wondering if any of you can tell me what the best way is to gut them? I have read that you need to be really careful to not push any of the inner fill into the secondary cat but not sure how to get it out without doing that? I don't have a tone of time to figure this out since they should be out in the next few days and will have to get them back in shortly after they come out. Any feedback would be greatly appreciated.


    Thanks

  2. #2
    Registered User ttboost's Avatar
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    Mark 'em, cut'em, gut'em, reweld 'em.

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    I gutted mine without cutting, but it's not the simplest task. I used a combination of some worn wood boring auger bits, a long cold chisel, a sledge hammer, some screwdrivers, and an air compressor with a blower nozzle. It took a bit of time and patience but in the end I was able to get all of the primary cat material removed and as far as I can tell the main cats haven't been affected.
    RS6 #1, 01E, 2.5" straight pipes, AMD Stage 1 6MT tune, 460awhp/530awtq on AMD's Mustang dyno. TOTALLED.. RS6 #2, Ebony Black Pearl on black/silver combination with carbon, up and running with 6 gears and AMD tune.

  4. #4
    Registered User ttboost's Avatar
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    I was fortunate enough to find some factory DP's cut off at the pre-cat. I used a 5lb sledge and a long bar/punch to pound it clean. Then bought some stainless and fabricated and welded the rest of the DP back together for fully catless DP's. However, If I DIDN'T find these, I would have cut mine, gutted them, and Tig'd em back together.

  5. #5
    Registered User Bigglezworth's Avatar
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    It's a solid couple of hours to do both sides using old fashioned drilling and pounding. The 'next time' I would elect to use an extra long pnumatic air chisel. NOTE. You will wear our the primary cats downstream once you gut and remove the precats. It's just a matter of time. Mine are stinking bad now as the hotter gasses from a turbocharged car burn things out quicker. I will either be cutting out and welding in some straight pipe, or puchasing a set of new piggies c/w high flow cats. Haven't decided yet.
    '02 S6 Avant Silver - Pokey | Carbon Black/Ebony RS6 w/ stuff - darn quick | '03 Daytona Grey/Ebony RS6 w/ more stuff - quicker yet | '91 NSX CDN issue with 6spd & BBSC - quicker yet and then some | '87 Buick GNX OEM clone w/ lots of stuff - quickest hands down

  6. #6
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    I just went through this with mine, and here are some things I learned:

    Like others recommend, I drilled holes first, then used the air chisel to break out chunks. The cat material is not brittle, so you are essentially cutting pieces out of the core and pulling them out as best you can. Long reach needle nose pliers help pull stuff out once you cut it free.

    For the drill, I used a long 1/4" bit. I also tried a long 1/2" masonry bit, but it did not work well. It tended to just pack the material down more than drill through. A smaller masonry bit might have worked better.

    The general strategy I used was to drill holes roughly in a circle about 1" diameter. Then I used the air chisel to "cut" between the holes until the piece in the middle was free and I could pull it out. After that, I used the chisel to carve chunks off the sides until I got back to the metal wall of the pipe. All this sounds good in theory, but it's pretty hard to drill the holes neat and tidy, and make clean cuts with the chisel. You end up just hacking at parts with the chisel sometimes until it feels like there is nothing left to hack.

    You definitely want to be careful about pushing the cat material too far up into the pipe. There is a bend downstream, and if you get something stuck past that bend, it's going to be tough to remove. I used a long air chisel, and you need to be extra careful with that since it digs through the material pretty easily and can push a piece up before you realize it. That said, I managed to get a pretty big chunk stuck up in the bend, and the way I got it out was to use a heavy copper wire (like 10 or 12 gauge from house wiring) and bend a hook into the end and carefully work it up past the stuck piece and pull it out. It took quite a few tries to get the hook to "set" and break the piece free. Once I was done, I used a telescoping mirror to look around the bend in the pipe and make sure it was clear.

    The chisel will get stuck, so the longer it is, the easier it will be to get back out. Rocking the chisel side-to-side when you are going in can help keep it from binding. The holes you drilled will help as well, since they open up the material and allow more flexibility for the chisel to move.

    There is more material up there than you think. There were several times I thought I was close to done, only to pull another 2" chunk out!

    I also made a tool out of a piece of 1" flat bar. I bent about 1/2" of one end to 90 degrees and ground the edge of the bent piece to a slight curve. I used this tool to reach into the pipe and scrape the sides. It wasn't required, but it helped.

    Finally, once I had chiseled and scraped out as much as I could, I put a 2" wire wheel on a long bit extender and used it to try and clean the sides of the pipe as best I could. Again, there was more crap up there than I expected. Reverse the drill occasionally to help break things up. Also, I did this with the pipe hanging upside-down so all the little pieces were falling out instead of in. When complete, I blew compressed air back through the pipe to try and get all any small pieces left behind.

    In the end, I probably spent about 4 hours working on them, but I definitely took my time, and the second one went quite a bit faster.

    These were the main tools:
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    These tools helped:
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    Wire wheel setup:
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    This is all the material from both cats (milk jug for reference):
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    Pipe hanging off of my press to keep junk from falling in:
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    View after it's cleared:
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  7. #7
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    +5000!!!!

    the only real way

    I drove an RS6 to work today! We have been traveling and super busy. Cars have been parked.

    Life is good


    Quote Originally Posted by ttboost View Post
    Mark 'em, cut'em, gut'em, reweld 'em.

  8. #8
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    I ended up cutting gutting and welding which was recommended by ttboost on here and I'm glad I did cause after they pulled the core out it made total sense why people were having such a hard time trying to cut and pound them out with a hammer. The cat is bonded to the inner pipe like glue and also seems to be made out of metal in there which makes it hard to even get it to come out in chunks. I paid $250 to have them both done and was worth it to me anyways.

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