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| D2 - Fuel and Exhausts Everything to do with getting fuel into the engine, and fumes back out again |
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#1
23rd June 2011, 03:48 PM
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De-Cat is it worth it ?
im going to de-cat the car tonight im thinking of just taking the cats off cutting into them and taking the honey comb out and welding back up with a tig welder and then putting it back on ?? what's the best way of going about this ?
gains ect... Last edited by Conan_the_Librarian; 23rd June 2011 at 04:20 PM. Reason: To stop any unwanted interest in the friends activities 
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#2
23rd June 2011, 04:28 PM
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For a non visible intrusion into the Cat take it off and cut out the top remove the inside and fit a through pipe and weld it back up. This will help gas flow. Just hollowing out a cat will induce turbulence. You will then have to code out the post cat lambas.
As for gains, added to a free flow exhaust and mapped to take advantage of the free flow you could see some gains.
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Conan (the Librarian) Watch it if you dare Currently, 2000 S8, Merlin Purple, Leather Pack 1, Winter Pack 1, SPAX adjustable suspension, AP Racing 6 pot front caliper, 385mm fully floating disks, EBC Yellow Stuff Pads, Black Diamond grooved rear disks and predetor pads, D2 Doctors Brake Block. 1997 4.2 A8SQ - the Projekt. 12 years and ongoing! 1997 4.2 A8SQ - Ming Blue. Restoration sat waiting; saved from the Scrapyard 2003 C5 Allroad 4.2Q - Cobolt Blue. Towing car. Laid up awaiting manual conversion. 2005 C5 Allroad 2.5TDi FE - Grey - Workhorse. 2015 Q3QS SLine - Daytona Grey. Lots of extras! Long Haired Admirals cutter. Previously 2003 C5 A6 1.9TDI FWD - Loaner from D2 Doctor Lifex 1997 S8 - Ming Blue. Loaned out and written off. I loved that car. My first engine swap after cambelt failure. 1996 4.2 A8SQ - Ming Blue. 178k on a cambelt! Trader's 8. Delivered to A8Parts at Lifex. 2003 2.8 A8SQ - powder blueish. Fill in for a while. Sold on. 1998 1.8T A4 Avant FWD. Ming Blue (there's a theme here), PEX for the 97 S8. And a list of non VAG going back 40 years before I saw the light. 
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#3
23rd June 2011, 04:36 PM
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>> You will then have to code out the post cat lambas
Conan, I'm sorry, I'm just curious, but how can we 'code out' the post cat lambdas? With VAGCOM? I didn't know it is possible. If cats are dead I would suggest installing new aftermarket custom made sport cats. I think it's better than just substituting with through pipe. This path is relatively cheap, I think about 500 pounds for everything. These cats won't be as dense as Audi original cats, but these will be cats, and not a pipe. Also, is it legal to drive without cats? Can you pass MOT without cats? I know aftermarket cats are OK for MOT. Questions, questions, questions...
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I'd rather drive on left
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#4
23rd June 2011, 05:18 PM
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On our cars aftermarket cats are ok up until 2001. After that the cats must produce results within the OEM tolerances. there is a post somewhere about the new MOT rules.
After cats can't be coded out with VCDS afaik but can be mapped out. Construction and use regulations require all cars after a certain year to have cats. Cars fitted with cats must pass the emissions test during the MOT. If you have cats fitted and pass the emissions test your ok. You will fail if you don't have cats (and you'll be registered on a database to that effect) or you fail emissions tests. If you have empty cats and pass the emissions test you comply with the rules!!!!!!!!! Running on LPG I passed all my emissions test and I had cats where cats should be!!!!!!!!!!!!!!!!!!! 
__________________
Conan (the Librarian) Watch it if you dare Currently, 2000 S8, Merlin Purple, Leather Pack 1, Winter Pack 1, SPAX adjustable suspension, AP Racing 6 pot front caliper, 385mm fully floating disks, EBC Yellow Stuff Pads, Black Diamond grooved rear disks and predetor pads, D2 Doctors Brake Block. 1997 4.2 A8SQ - the Projekt. 12 years and ongoing! 1997 4.2 A8SQ - Ming Blue. Restoration sat waiting; saved from the Scrapyard 2003 C5 Allroad 4.2Q - Cobolt Blue. Towing car. Laid up awaiting manual conversion. 2005 C5 Allroad 2.5TDi FE - Grey - Workhorse. 2015 Q3QS SLine - Daytona Grey. Lots of extras! Long Haired Admirals cutter. Previously 2003 C5 A6 1.9TDI FWD - Loaner from D2 Doctor Lifex 1997 S8 - Ming Blue. Loaned out and written off. I loved that car. My first engine swap after cambelt failure. 1996 4.2 A8SQ - Ming Blue. 178k on a cambelt! Trader's 8. Delivered to A8Parts at Lifex. 2003 2.8 A8SQ - powder blueish. Fill in for a while. Sold on. 1998 1.8T A4 Avant FWD. Ming Blue (there's a theme here), PEX for the 97 S8. And a list of non VAG going back 40 years before I saw the light.
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#5
23rd June 2011, 05:37 PM
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Mike, correct as per!
Post CAT lambdas can't be coded out unless you have a stage 2 type remap that removes the DTC string for those probes. Really isn't much good just knocking the innards out of the shells as Mike said, this causes disruption to the exhaust gas flow that causes more of a restriction Tywyn the original CATS!!
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#7
23rd June 2011, 06:33 PM
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As many of you know, I took the 'custom sports cats' option. Slightly nicer noise, teeny bit better performance, much cheaper (a little over £400 for 2 cats fitted) and no problems with an MOT. I thought I had a problem when the engine management light came on after 9 months or so and Vagcom said cat failure, but it went off again a day or two later and Vagcom was clear again - probably a bit of gubbins (BP Ultimate not perfect then!). But the fitter was happy to take the car back in if the problem recurred as the cats were guaranteed for life.
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#8
23rd June 2011, 06:49 PM
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mmmm im not sure what to do now then if i de cat it tonight and put a pipe through will that put a light on the dash or disrupt anything ?? as it may be some time before i get around to remapping it ??
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#9
23rd June 2011, 08:21 PM
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Your 2 post cat Lambas will report a fault which may light the dash up.
__________________
Conan (the Librarian) Watch it if you dare Currently, 2000 S8, Merlin Purple, Leather Pack 1, Winter Pack 1, SPAX adjustable suspension, AP Racing 6 pot front caliper, 385mm fully floating disks, EBC Yellow Stuff Pads, Black Diamond grooved rear disks and predetor pads, D2 Doctors Brake Block. 1997 4.2 A8SQ - the Projekt. 12 years and ongoing! 1997 4.2 A8SQ - Ming Blue. Restoration sat waiting; saved from the Scrapyard 2003 C5 Allroad 4.2Q - Cobolt Blue. Towing car. Laid up awaiting manual conversion. 2005 C5 Allroad 2.5TDi FE - Grey - Workhorse. 2015 Q3QS SLine - Daytona Grey. Lots of extras! Long Haired Admirals cutter. Previously 2003 C5 A6 1.9TDI FWD - Loaner from D2 Doctor Lifex 1997 S8 - Ming Blue. Loaned out and written off. I loved that car. My first engine swap after cambelt failure. 1996 4.2 A8SQ - Ming Blue. 178k on a cambelt! Trader's 8. Delivered to A8Parts at Lifex. 2003 2.8 A8SQ - powder blueish. Fill in for a while. Sold on. 1998 1.8T A4 Avant FWD. Ming Blue (there's a theme here), PEX for the 97 S8. And a list of non VAG going back 40 years before I saw the light.
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#10
23rd June 2011, 09:04 PM
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ah dam it i wont risk it just yet then, i will focus my energy on getting it all perfect again before further mods ie sort the intake manifold out and give the water ingress i had time to settle just a shame that its not all perfect before gti as im sure it will affect my over all time's
 but never mind
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