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N75

Discussion in 'A4/S4 forum(B5 Chassis)' started by Lee Goodall, May 12, 2008.

  1. Lee Goodall
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    Lee Goodall ..got my head together!

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    Noticed a drop in boost over the weekend so I ran a diagnostic check and it turns out my N75 boost control solenoid is faulty.

    Is it worth going for an N75J as a replacement?.. I'll be fitting a new turbo and getting a remap too in the next couple of weeks.
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  2. docurley
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    docurley Moderator Staff Member Moderator

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    It's been said that mapping will map out any benefits of the J valve but who knows.
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  3. Lee Goodall
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    Lee Goodall ..got my head together!

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    That's what I was thinking as the boost will be increased to whatever level is required anyway so I'll probably stick with the N75.
    Cheers.
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  4. p-torque.co.uk
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    p-torque.co.uk Member

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    I would stick to the normal N75 if you are having it mapped up.

    The J valve is sometimes ok, but can cause limp mode, especially when re-mapped.

    If you fancy a chat about re-map options, feel free to e-mail us, or call us on 01902 324584 :)
    #4
  5. Lee Goodall
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    Lee Goodall ..got my head together!

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    Cheers.

    I've got somebody lined up for the remap but I'm always interested in better offers so I'll probably be in contact.
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  6. p-torque.co.uk
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    p-torque.co.uk Member

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    No problem!
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  7. Lee Goodall
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    Lee Goodall ..got my head together!

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    ..fitted the new N75, cleared the fault code and the turbo boost is still only hitting 0.3 Bar / 4.3 PSI!?! Checked for fault codes again and still getting:-

    01262. boost pressure control solenoid - N75

    I'm guessing it's the wiring although it all appears to be fine.. Looks like my turbo is def not getting fitted over the weekend now!! Fnck it!!
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  8. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    check the wiring, but its not neccesarily the valve thats broken

    if the wastegate was jammed open the turbo wouldnt boost, the ecu sends signals to the N75 to raise the boost pressure and doesnt see any rise. The ecu can only assume the fault lies with the valve ignoring its signals.

    I dont know if these turbos are known for failing wastegates, but i have heard that the valve can break off the arm on other turbos. The turbo on my car was replaced about 30k ago (130k miles) for identical symptoms according to the service history (it was before i owned it) so it is perhaps an issue with high mileage K03's?
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  9. Lee Goodall
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    Lee Goodall ..got my head together!

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    I've got my new turbo to go on so I'm trying to get hold of a new actuator too. Probably be best to fit the turbo and actuator then.. if the boost levels rise again then it was obviously one of the two parts.

    If not then I'll investigate further.. My N75 was starting to rust anyway so no harm in replacing it I suppose.

    The current turbo has covered about 103000 miles and is leaking oil slightly so maybe it's lost the will to live!
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  10. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Stay with the n75 F, i tried a J and although it gave slightly better boost, it surged up and down under load
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  11. AUDI TURBO
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    AUDI TURBO Member

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    i agree with byzan exactly same as my j valve
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  12. Lee Goodall
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    Lee Goodall ..got my head together!

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    Yeah fitted the standard N75 but still low on boost.. hopefully the problem lies with the turbo/actuator which will by Tuesday (hopefully) be replaced with SP51R turbo and replacement actuator.. with many thanks to byzan.
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  13. hiltoa
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    hiltoa VAG erfahren

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    I have an N75J on my AJL and while boost doesn't surge up and down it seems to have 2 modes - 'normal' where I see 12 to 13psi between 3.5k and 5.5k rpm in the higher gears, and 'disappointing', where it builds boost noticeably slower, and struggles to reach 11psi. I assume 'dissappointing' isn't as bad as 'limp mode' would be... I get it roughly 30% of the time at the moment.:confused:
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  14. Lee Goodall
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    Lee Goodall ..got my head together!

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    The new turbo and actuator are on and all seem to be working correctly but I'm still getting the same fault code.. 01262. boost pressure control solenoid - N75

    If I select the fault it also says N75 circuit open.

    Any suggestion would be brilliant?.. want to get on with remap but need to sort this out first!! :doctor:
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  15. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    As Aragorn said it could be broken wiring in the plug. If you just pull the wastgate pipe and see what it boosts at then,i bet it will be ok but will put you into fuel cut. That at least will test your wastegate seal and spring tension on the actuator etc.I will try and find the test values for the wiring of the N75 for you
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  16. Jimbo.King
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    Jimbo.King Member

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    If it’s coming back with open circuit there must be a broken wire in the loom or bad connection to the N75,

    Pull the rubber boot back that’s on the electrical connector that plugs to the N75, see if there's a break there to the pins in the holder,

    If not there could be a break in the loom, while the rubber boots pealed back get hold of each wire and pull slightly to see if there are any breaks in that small part of loom,

    Make sure the connectors in the plastic plug aren’t corroded to give you a bad contact.
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  17. Lee Goodall
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    Lee Goodall ..got my head together!

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    I'll hopefully get to give the wiring and connections a good check over the weekend.. been kind of manic at work this week!

    I'll test the actuator too to be sure.

    Cheers for the input.
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  18. Lee Goodall
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    Lee Goodall ..got my head together!

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    If you do manage to get the values it's be much appreciated.. I'll have to start paying you at this rate :thumbsup:
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  19. AUDI TURBO
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    AUDI TURBO Member

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    I take it as i might at some point buy a new acuator they have to be set up?? and bin told they make no difference to performance
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  20. Lee Goodall
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    Lee Goodall ..got my head together!

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    Setting up and fitting a new actuator means taking your turbo off.. once it's off though actually fitting and setting up the actuator is straight forward.

    Think most people change them due to age but if yours is fine I'd leave it as it's a good few hours of work.
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  21. Lee Goodall
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    Lee Goodall ..got my head together!

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    Ha found the problem..
    [​IMG]
    the wire had broken inside the sleeve (pulled the sleeve apart for photo).
    Rewired the connector and she's boosting like a good'en :yahoo:
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