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Low back pressure with TBE

Discussion in 'A3/S3/Sportback (8P Chassis)' started by Fast,not furious, Nov 4, 2008.

  1. Fast,not furious

    Fast,not furious Dealing with an OCD

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    Now my custom turbo back exhaust has been fitted,(by Exhausts UK,Sheffield)the car's suffering with boost problems. Steve Jr at Statller reckons it's the exhaust that's causing the problem,and recommended putting the old exhaust back on,and then data logging,but obviously that's gonna cost...and then a replacement(maybe my custom one,modified?)or Milltek will have to be fitted again...more money...
    Although it has a 200 cell sports cat,the complete system is flowing too well,so not creating enough back pressure,causing the turbo overboost,so i'm losing torque.
    What should i do? Spend more at Exhausts UK,fitting another cat or something to restrict the flow? Spend even more and go full Milltek?

    I've no idea what i should do next! I've even considered just having the Milltek downpipe and sports cat,but the combination still might not flow correctly with the rest of the system.

    Its currently a 3" downpipe,200 cell sports cat,2.5" pipe,mid silencer,2.5" pipe,cobra rear box.

    I'm running a GIAC hammer map and Forge CAI,both worked seemlessly before the exhaust went on.
     
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  3. dunk

    dunk Member

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    as a general rule, low back pressure from a highflow cat and good exhaust is usally a good thing - it is going to give you less lag, lower exhaust and turbo temperatures therefore more airflow and pressure with less stress on the engine components.

    what you may need is a custom remap to ensure that you have correct boost pressure and fuelling for the new setup, rather than undo the (presumably good and working properly) effects from the exhaust/cat
     
  4. boggysv

    boggysv Member

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    <beer induced thought>

    why not try to plug your exhaust outlet and see what happens?
     
  5. Fast,not furious

    Fast,not furious Dealing with an OCD

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    :tumble:
     
  6. jonnyc

    jonnyc Member

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    Its half 4 mate!! haha..
     
  7. Fast,not furious

    Fast,not furious Dealing with an OCD

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    Could it be the fuel pump??
     
  8. Sohrob

    Sohrob Member

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    i am very dubious as to how good custom systems are, if you look at a miltek exhaust it has been designed and developed for that vehicle.

    On previous cars i have had custom exhausts and they are just made to fit there and then without any development or research into flow rates, where the bends should be etc etc.

    If it was me i wouldnt spend anymore money and go back to std or get a miltek.

    I cant see it being your fuel pump but maybe take it into Audi for a diagnostics check (be prepared to loose your map thoug!!!)
     
  9. crazylegscrane

    crazylegscrane Active Member

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    :iagree: back to standard or miltek and if that sorts it get your money back for the custom exhaust as it dosen't seem fit for purpose
     
  10. Fast,not furious

    Fast,not furious Dealing with an OCD

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    Update...

    It was the fuel pump!

    Exhausts Uk put me in touch with JBS Auto Design,and after a chat with them,the car was booked in for a health check....and the patient has responded well to surgery :tapedshut:
     
  11. jonnyc

    jonnyc Member

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    Eeeeesh what did I say ;)

    Its a bit of a worry to hear that a fuel pump in an S3 has gone bad though, can you expand on the problems?
     
  12. Fast,not furious

    Fast,not furious Dealing with an OCD

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    Jonny

    Mine was one of the earlier 'H' pumps,which some are having problems with. It seems that it was just unable to supply enough juice for the extra demands the exhaust seemed to make. It was fine before the exhaust went on,so i guess the free flowing exhaust and extra horses were asking more than it could give,hence loss of boost. Logs showed it only able to sustain 110 bar,but with the new pump,she's now holding 140
     
  13. jonnyc

    jonnyc Member

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    Ah cool..

    Its more like 110bar and 140bar now.. The FSI fuel rail pressure is immense!

    Glad you got it sorted out anyways mate :)

    Jonny
     
  14. Fast,not furious

    Fast,not furious Dealing with an OCD

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    That's what i said :redface: (does a quick edit!)...i thought that sounded low as soon as i wrote it...no wonder i had problems...lol

    Yeah,it's grand now mate
     
  15. jonnyc

    jonnyc Member

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    lol, sorry must have read it wrong ;)

    Have fun mate!
     
  16. Fast,not furious

    Fast,not furious Dealing with an OCD

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    Lol,yeah - i reckon you've been pulling to many G's round the circuit recently and your eyes are still blurred!:unsure:
     

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