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1.8t 190 fluctuating boost

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by hitman1978, Jun 6, 2012.

  1. hitman1978

    hitman1978 Member

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    Hi, I've recently had revo stage 1 installed and the boost seems to be fluctuating, it peaks around 22psi but bounces around between 15 psi and 18 psi, anyone any ideas as what could be causing this?
     
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  3. boost-addict

    boost-addict Active Member

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    not sure, best ringing revo and or go back to them.

    but could be some thing simple as a n75 but then could be a fault in the map.

    they tuned it so its best to get it sorted by them.
     
  4. Paul @ Unit 9 Remaps

    Paul @ Unit 9 Remaps Site Sponsor
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    N75 or Maf, could also be boost leak, id check in this order too
     
  5. hitman1978

    hitman1978 Member

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    This might sound really dumb, what and where is the n75 valve?
     
  6. Paul @ Unit 9 Remaps

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    its on the turbo intake pipe off the top of my head, little black plastic thing around near the maf area
     
  7. hitman1978

    hitman1978 Member

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    Do you mean the recirculating valve?
     
  8. Paul @ Unit 9 Remaps

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    no mate smaller than that, its square
     
  9. hitman1978

    hitman1978 Member

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    I'm absolutely clueless with these engines, is it going to be a main dealer part or is there anywhere you'd recommend to get parts from?
     
  10. beachbuggy

    beachbuggy Well-Known Member

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    Assume you have a boost gauge to view this?

    Boost is load dependant and also temperature. You may just find its the way it's mapped or the way you drive! Only real way to test is to run a WOT run from 2k to redline in 3rd and see what you get, any other way is near pointless to measure.
     
  11. hitman1978

    hitman1978 Member

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    I'm definitely dumb now, what's a wot run?
     
  12. boost-addict

    boost-addict Active Member

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    Wide Open Throttle

    basicly full throttle

    do you have a boost gauge? get a vid from 2k 3rd gear to read line. full throttle
     
  13. hitman1978

    hitman1978 Member

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    Yes I have a boost gauge, I'll get a vid tomoro and try and post it up
     
  14. hitman1978

    hitman1978 Member

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    I've managed to get a vid and uploaded to YouTube, but damn thing won't display the url, my post is a4 1.8t revo stage 1
     
  15. beachbuggy

    beachbuggy Well-Known Member

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    Ok, think I've seen your vid. I'd say almost certainly it's just the way it's mapped. Peaking at 22psi is normal for Revo! Very spikey as they over shoot the requested boost, then the n75 tries to regain control of the boost and by nature fluctuates which is the variable boost you see before it stabilises and drops. The n75 in affect oscillates the boost until the required level is met, the bigger the variation ie over shoot the more it needs to oscillate to regain control. A sensible map will have less over shoot thus the oscillation are more stable and the boost fluctuates less or not at all.

    Revo are spikey which results in what you see. Nothing wrong with it just a different way of tuning.
     
  16. hitman1978

    hitman1978 Member

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    Thanks for the reply, it seems its sorted now aswell, doesn't over boost anywhere near as bad now I've refitted the larger pipe from intercooler to throttle body? I noticed it had managed to make its way about 10mm down the flange it connects to, don't suppose you know anywhere that sells aftermarket ones, mines rather soft, cheers
     
  17. beachbuggy

    beachbuggy Well-Known Member

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    Forge is the only company I know that sells aftermarket boost pipes.
     
  18. hitman1978

    hitman1978 Member

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    I've been looking on there site, think I've found the right tip, with the 5 connections on it, but can't find anything listed for the pipe I'm after :(
     

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