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AGU - Disconnected pipe from actuator to N75. Full boost?

Discussion in 'A3/S3 Forum (8L Chassis)' started by Stanley, Jan 15, 2011.

  1. Stanley
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    Stanley Member

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    [Jan 15, 2011]
    Ive done some digging and found that my N75 is faulty by taking the pipe off from the actuator.

    What does this actually do, and is it 'safe' to drive like that?

    Will it make the fuel mix too lean and cause DET? Or will it puff the turbo?

    Cheers all, Stan.
    #1
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  3. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 16, 2011]
    Removing the pipe from the actuator will over boost the engine leading to potential catastrophic failure of the engine from everything you think it will... it will go lean melting pistons but more likely bend or throw a rod out the side of the block...
    If you believe your N75 to be faulty, unplug the electrical connector and it will run at actuator pressure... do not disconnect the pipes and do not run the engine with no boost control (actuator pressure is boost control... limits to 5psi or so)... it will cost you...

    <tuffty/>
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  4. Stanley
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    Stanley Member

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    [Jan 16, 2011]
    I ran it like that for a short while to test the functionality of the N75 and I have got away with it!

    My cars been remapped and i suspect its a very rich map to keep it safe.

    New N75 will be ordered soon!

    Just out of curiosity, what PSI was i running at without that pipe connected?

    Cheers for the reply, Stan.
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 16, 2011]
    Not sure as I have never done it... can I ask what made you think the N75 was faulty? very rich doesn't mean safe...

    <tuffty/>
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  6. bbewekim
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    bbewekim New Member

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    [Jan 16, 2011]
    Plug it in to vcds or lite etc. Run block 007 I think, you need to look or log the duty cycle. That will show you what the n75 is requesting. E.g when at full throttle it should request 100% or there abouts... This must be logged with the car driving though.
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  7. sportstractor
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    sportstractor Chugger

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    [Jan 16, 2011]
    Ha well all you have done is taken control of the turbo away from the management. Could it not be that because that it's running so rich (maybe a boost leak or knackered maf) that the ecu is going into soft limp mode and purposely restricting boost. Have you checked for fault codes etc? You can also check the duty cycle of the n75 using vagcom to check functionality.
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  8. sportstractor
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    sportstractor Chugger

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    [Jan 16, 2011]
    Snap
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  9. jay1601
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    jay1601 Well-Known Member

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    [Jan 16, 2011]
    anyway to test it without VAG COM ?
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  10. Welly
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    Welly VX220 SC Driver :)

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    [Jan 16, 2011]
    Disconnecting the actuator pipe and getting full boost doesn't necessarily mean that the N75 is faulty... there are other factors that can contribute - especially on the AGU.
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  11. Stanley
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    Stanley Member

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    [Jan 16, 2011]
    I figured i'll try an N75 as its the cheapest method so far. I can get one for £5 so will try that.

    My symptoms are a lack of boost pressure. I have no guage, but its immediately noticeable. Feels like an N/A 1.8 20v.

    It happens intermittantly which is what baffles me. Some days its fine, others it not.

    Disconnecting N75 at the electrical connector makes no difference. However, blanking the actuator to N75 pipe makes it fly.

    As i say, N75 is my first port of call.
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  12. sportstractor
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    sportstractor Chugger

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    [Jan 16, 2011]
    as said, boost leak or another problem throwing it into limp mode. It will cut the boost as its designed too. I doubt its the n75. You need to get it on some sort of diagnostics and there will more than likely be a fault code.

    Mine was doing the exact same thing and turned out to be a leak. The plan of changing parts from least to most expensive probably isnt going to work very effectively lol
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  13. Stanley
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    Stanley Member

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    [Jan 16, 2011]
    Im tempted to scrap the stupid nazi piece of ****. Ive had all sorts of cars and never had as much bother as i have with this. Hitler cant build cars. Fact.
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  14. s3dave
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    s3dave TFSI Hybrid Supporter

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    [Jan 16, 2011]
    lol....
    There will be an explanation for it, where are you? can you get hold of vcds from anybody
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  15. DenCar
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    DenCar Member

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    [Jan 16, 2011]
    Oh Boy!!

    DC
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  16. dany2k
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    dany2k Member

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    [Jan 16, 2011]
    so basically, if u unplug the electrical connector to the n75, you an see if your n75 is faulty or not?
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  17. jay1601
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    jay1601 Well-Known Member

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    [Jan 17, 2011]
    Just disconnected the electrical connection on the N75 valve, made no difference to mine, still won't boost above 3/4 PSI

    Think I'm gunna have to try and find someone with Vag-com
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  18. sportstractor
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    sportstractor Chugger

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    [Jan 17, 2011]
    Well as said, if you disconnect n75 electrical plug the turbo will run at actuator pressure! Aka 5psi.

    You have a fault that is more than likely throwing it into limp mode, really would pay to get it checked for DTCs (fault codes)
    #17
  19. jay1601
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    jay1601 Well-Known Member

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    [Jan 17, 2011]
    I have no fault codes, I check daily. I've checked for boost/vac leaks. Can't find anything. Think I'm gunna have to see if I can find someone with VCDS that could do some logs for me
    #18
  20. s3dave
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    s3dave TFSI Hybrid Supporter

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  21. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jan 17, 2011]
    I had a fault in the wiring to the N75, which made it intermittantly drop to actuator pressure. After investigating (read: prodding at it somewhat) the wiring stopped working completely. Spliced a new section of loom in and the power returned.

    As people have said, you've not proved the N75 is faulty, you've just proved that the turbo itself is fine. The N75 might be working perfectly, and the wiring is at fault, or the ECU could specifically be requesting no boost due to a fault.

    Dont start changing parts until you've scanned it for fault codes.
    #20
  22. stumpy83
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    stumpy83 one legged wonder

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    [Feb 6, 2012]
    im getting similar issues, wont boost over 3 psi
    been scanned a couple of times and onlt DTC's come up was ABS fault (engine / trans / abs module shows all the same fault)
    #21
  23. jay1601
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    jay1601 Well-Known Member

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    [Feb 6, 2012]
    new MAF fix the problem with mine.

    old MAF boost to 10/11PSI new MAF will boost to 15PSI (stage 1 map figures)
    #22
  24. stumpy83
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    stumpy83 one legged wonder

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    [Feb 6, 2012]
    do you know the blocks i need to check for the MAF please?
    #23
  25. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Feb 6, 2012]
    #24
  26. doughty29
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    doughty29 Member

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    [Dec 9, 2012]
    ive got the same problem, did you find out what it was? thanks
    #25

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