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Changed N75, still problems

Pornstarr Apr 9, 2008

  1. Pornstarr

    Pornstarr Member

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    I changed my N75 valve today, finally.

    But I'm still getting a positive deviation in the boost.

    Now, I've also got a low reading on the Air intake temp gauge (G42).
    I wonder if that's causing the fault?

    If not that, what else?

    I was hoping to have the car running right after that, but it's disappointing to still have the engine cutting back power :(
     
  2. bahnstorm.net

    bahnstorm.net Member

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    have you pressure tested it?
     
  3. Blue_Thunder

    Blue_Thunder Well-Known Member

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    Hope for your sake it's not one of the wastegate actuators causing the overboosting.

    As Bahnstorm suggests, get a pressure test sorted.
     
  4. Pornstarr

    Pornstarr Member

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    Yeah, I hope it's not the wastegates too.

    However, the Log's I've done on the boost block show that it's only spiking, rather than holding higher boost all the time.
    For half a run, it'll be within the +/- 20mbar tolerance. It'll spike just as I first hit boost in 1st gear. And if I hold off the boost before a run, it'll spike the first time I hit boost.
    Then it goes low for a little while, then levels out, but comes on really slowly.:uhm:
     
  5. Blue_Thunder

    Blue_Thunder Well-Known Member

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    Can you post some third gear logs up from block 115?
     
  6. Blue_Thunder

    Blue_Thunder Well-Known Member

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    Oh, and your boost will spike in 1st gear as obviously it rises much quicker than in any other gear.
     
  7. Pornstarr

    Pornstarr Member

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    I could never get my GT-four to peak boost in 1st gear, there just wasn't enough load to bring it full before I ran out of revs.

    Either way.

    Heres a WOT run in 3rd gear I did the other night. These readings are symptomatic of all my runs.....

    [​IMG]
     
  8. Blue_Thunder

    Blue_Thunder Well-Known Member

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    The specified/actual boost looks spot on there. Really need to do a log at 100% throttle (mash it!) to be sure though.

    MAF reading is lower than you'd expect. What air filter are you using, and when was it last changed?
     
  9. Pornstarr

    Pornstarr Member

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    Standard air filter i suspect.
    I've had the car 3 weeks now? Not changed the filter.

    Will pull it out and have a look tomorrow.
    Gonna look into a new fuel filter too. Apparently it's not a normal service item?! If that's 120,000 miles old, then there's definately gonna want a change.

    That log there.....that is 100% WOT. Flat to, and buried in the floor just after the logging began.

    It's so weird.
    The car goes like a greased weasel once the error code is removed. Get serious acceleration in 1st and 2nd....then it all goes away. Pull over....error code back.


    Can anyone with a standard car post a similar log, just so I can see the main differences? Please.
     
  10. Blue_Thunder

    Blue_Thunder Well-Known Member

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    The 4th column in Block 003 shows Throttle angle doesn't it?

    Over 7 seconds for FATS is well off the pace. Would defo not expect the Max Boost Limit exceeded to flag up with those boost readings.
     
  11. bahnstorm.net

    bahnstorm.net Member

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    check the tb see if its opening completely,if it is check the sensors on the acc pedal
     
  12. Pornstarr

    Pornstarr Member

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    I thought the throttle valve reading was weird, but then discounted it as just not understanding the readings.

    I presume, at WOT, it should read 100% then? So, it's only giving me half throttle?
     
  13. bahnstorm.net

    bahnstorm.net Member

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    yes you should see 100% at full throttle opening,try doing a tb re allignment,ign on and leave it for a few mins,you will hear it re set,if that fails to work,disconnect the battery for a while,sometimes unplugging the ecu for a while seems to rectify this too,failing that its either sensors or tb itself
     
  14. ALPINE

    ALPINE Yes its diesel, now cry u lost

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    sorry to hijak your post but your problem is the same as what my car did. it is slightly better now i have replaced the stock dump valve and fitted a forge. i have also fitted a 8" cone filter, re-located horn to were origanal air box was and plumed in a dirty great induction pipe! (hence the horn move)

    the throttle responce is alot better and it seems to "hold its boost" alot better. it still lags a little but vagcom threw a n75 error at me so i will be replacing that with a n75j. it also sounds awasome as you can hear turbo spooling up, and it dumps when i change gear now!!

    not really solid advice you were looking for but shared info is good info! the mods seemed to help my car!:yahoo:
     

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