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Pre-cat removal 2.5 & Exhaust options

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by S4_dan, Jan 28, 2014.

  1. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 28, 2014]
    Just bought a fully gutted pre-cat for a massive sum of £1.70! £6 postage so not all bad :)

    Why not gut my own? Well I'd rather keep one in good shape in case of future problems/issues/MOT's etc etc. And at £1.70!!!!

    So, I know access is easy at the turbo end but the other end? Is it access from under car or do I need to drop the full system to swap it out?

    I'm hoping it may alleviate the lack of torque/power issue on my 2.5.



    I know there are two more cats a bit further along and will look at having them removed in the future.

    Am I right in saying that after the cats is one silencer where the pipes split and lead to the rear boxes on each side?

    If so, has anyone removed the middle box and left the two rear boxes

    or

    Leave the middle box and removed the rear boxes?

    Cheers,

    Dan
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  2. adamss24
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    adamss24 Well-Known Member

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    [Jan 28, 2014]
    It does not make that much effect to be honest ! I still run mine...but no main cats though !
    #2
  3. MooLard
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    MooLard Member

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    [Jan 28, 2014]
    I guess the engine management system limits any big differences but in the past on other cars I've generally noticed the turbo spools up / kicks in a little sooner.
    #3
  4. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 29, 2014]
    What did you replace the main cats with Chris? Something homemade or a purchased pipe?
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  5. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 29, 2014]
    Fingers crossed it might help my no torque issue below 2000 rpm then.
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  6. AlexGSi2000
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    AlexGSi2000 Well-Known Member VCDS Map User

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    [Jan 29, 2014]
    I have no cats in mine, passes its MOT every time.
    I have a full stainless system, with two silencers either side on the rear tail-pipes.
    #6
  7. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 29, 2014]
    Do you still have the pre cat in?

    What does your sound like then? Any videos?
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  8. AlexGSi2000
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    AlexGSi2000 Well-Known Member VCDS Map User

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    [Jan 29, 2014]
    Pre-cat pipe is still there but the innards have been removed.

    It sounds really good to be fair, I have a few more recent videos which I can upload, this one is fairly old - it sounds a little different now due to the engine running properly. (a lot of turbo blow-off noise in this, its a lot less now!)

    [​IMG]
    #8
  9. VagCabby
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    VagCabby Active Member

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    [Jan 29, 2014]
    I gutted my pre cat and main cat last week on the 2.5tdi 163. The diffence is amazing car is alot more responsive and suprisingly smokes less!

    I did the pre cat first and it made bugger all difference so I did the main cat a day later and that made the difference.

    to remove the pre cat the easiest way is

    1. Unbolt the 3 bolts holding the pre cat to the turbo and loosen off the pre cat from the turbo

    2. Get under the car and remove the drive shaft guard above your nsf drive shaft

    3. Unbolt the front exhaust mount (held on by two bolts) this allows the access to a pita bolt!

    4. Rach up from under the car and unbolt the 3 bolts secueing the pre cat to the exhaust

    5. Pull the pre cat out from the top of the engine bay.

    once you have done it once it takes about 10 mins to remove
    #9
  10. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 29, 2014]
    Good info there VagCabby.

    Cheers, I'll have a go as soon as I get chance. Do you only have one main cat on your system? Mine has two I'm led to believe. Not looked under the car at the front yet.

    Cheers.
    #10
  11. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 29, 2014]
    Sounds good. What causes the blow off noise then? Did you turbo whistle a little before doing the exhaust?

    Dan
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  12. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jan 29, 2014]
    Or, buy my system with it's lovely shiny stainless tips and gut away to your hearts content, and then keep your system perfect to replace when you sell it :icon_thumright:

    [​IMG]
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  13. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 29, 2014]
    Is that a standard system James?
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  14. adamss24
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    adamss24 Well-Known Member

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    [Jan 29, 2014]
    It was a custom made 3" downpipe splitting into 2x 2.25" twin exhaust branches.


    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    #14
  15. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 29, 2014]
    Looks sweet! Does she sound good?
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  16. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jan 29, 2014]
    Yep.
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  17. adamss24
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    adamss24 Well-Known Member

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    [Jan 29, 2014]
    If you're talking about mine (!), it sounds lovely on idle- nice burble on tick-over and gets bit throaty as the revs increase but no drone on long motorway runs ! One of the best exhausts i've heard in a long time...
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  18. VagCabby
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    VagCabby Active Member

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    [Jan 29, 2014]
    no worries

    mine goes from the pre cat into a very big main cat the a long single pipe into a large silencer which splits into 2 and goes to 2 back boxes I think yours will split after the pre cat due to being a quattro, mine is FWD :)
    #18
  19. S4_dan
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    S4_dan Fire up the Quattro! VCDS Map User

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    [Jan 30, 2014]
    If it was a custom system I may have been tempted James. Looking for a bit of growling under throttle plus free flow in the hope I could restore my no torque issue before 2k rpm. At least that's what I keep telling myself. Lol
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  20. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jan 30, 2014]
    No problem, I'll be ebaying my standard system soon and just wondered if it was any use for you to gut the cats etc off the car whilst still keeping your original set up in one piece.
    #20
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