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  1. #1
    evomaster3000's Avatar
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    1.9 TDI AFN 110 boost control problem, help

    Just wondering if anyone can help, got a boost control issue since i've cleaned out the VNT.

    Anyway my issue is this, I have a boost guage fitted so i knew previous pressures etc, since i re-built the head and cleaned out the turbo it's been high boosting 20+psi @ motorway speeds on full throttle it will instantaniously hit 30psi!!!!

    This is not good atall! and thus limp home mode has activated twice.
    So i've been driving with a carefull eye on the boost until i had a chance to change the actuator setting as i think i freed it's movement to easily when re-building it.

    Since i adjusted the boost (took a few adjustments to get it right) it now boosts ok (not over 20psi) tho the N75 and actuator seem to have no adjustment ie as if the N75 is not working as there is now no vacuum going to the actuator on idle as there was in previous tests.

    The result is the car has the vanes set at one position, and is very laggy, boost no longer picks up on throttle but is more according to revs.

    But not having any fault codes to read? i'm poking around in the dark.

    An idea for you of the tune:
    110 bhp Audi A6 1.9 TDi
    S/S cat back Exhaut
    Pannel filter
    Tuning box
    FMIC
    EGR disconnected (but not blanked ATM)
    Just done head re-con and Turbo VNT cleanout.

    I've double and tripple checked the vacuum pipes and electrical connections and cannot see anything amiss there.

    I'm stumped really, and until i get fault codes read i'm a bit stuck but i'm sure that will throw up loads of stuff which will be indecisive of the issue i'm sure.

    I'm sure it's nothing to do with the maf/fueling as when on boost (above 2200rpm) it performs well and i can still overtake at less than motorway speeds, but @ 70mph boost is at 20psi (full throttle) still (obiously no VNT correction happening) and will go in limp mode, which limits fuelling aswell as boost hits 9-10psi but if u floor it performance is worse than "light footing it" as i call it.

    Anyway anyhelp much appreciated.

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  3. #2
    dieselfitter251's Avatar
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    Hey man, you're way beyond me in experience. You ran the car through measuring block on vagcom to monitor the car while it's running and logged the results? It may not be throwing fault codes but it may break down what's happening as you go through the rev range... It does sound as though the N75 isn't happy. If it's getting no vac in idle doesn't that explain a portion of the massive lag your experiencing? Do you have a spare N75 to swap with?
    Also, have you tried forcing fault codes? i.e., disconnect the N75 and see what happens, if there's no change then it may be the cause or part of the cause? Is there an upgrade for the N75 on the AFN engine? The original may not be able to handle your mods, tho I think this is unlikely.
    Like I said, a bit beyond my experience but I'd just do the ole' make a list and cross off everythig you've checked.... MAF sensor to boost leaks etc......
    Keep us updated.
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    Dieselfitter 251
    A4 avant '97 1.9tdi q
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  4. #3
    evomaster3000's Avatar
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    Well i messed around with the N75 and it seems it has been plumbed in wrong so i swaped the atmos and turbo feeds and it seemed to work. Tho it puzzles me how long it's been working fitted wrong way? and why it gave up?

    Tho the Actuator needed adjusting, so did that, now it all seems ok. Tho a couple of times it has stoped working so i think the N75 is on it's way out.

    I really need to get myself a VAG-com any reccomemendations?

  5. #4
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    i managed to find Release 3112n of vag-com for a free download im sure if i had the plug id have it all sorted but then i maybe well of i havent bothered looking into it more as i dont have a laptop....yet

  6. #5
    dieselfitter251's Avatar
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    Quote Originally Posted by evomaster3000 View Post
    Well i messed around with the N75 and it seems it has been plumbed in wrong so i swaped the atmos and turbo feeds and it seemed to work. Tho it puzzles me how long it's been working fitted wrong way? and why it gave up?

    Tho the Actuator needed adjusting, so did that, now it all seems ok. Tho a couple of times it has stoped working so i think the N75 is on it's way out.

    I really need to get myself a VAG-com any reccomemendations?
    Got software and cable from ebay... about 10 quid.
    Ford Mondeo 2.0i Durtec Ghia X Estate
    Leather / Dog Hair.



    Dieselfitter 251
    A4 avant '97 1.9tdi q
    a.k.a. STINKY
    [B]250k!
    ..she's gooooonnnne!!!!

  7. #6
    evomaster3000's Avatar
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    Quote Originally Posted by dieselfitter251 View Post
    Got software and cable from ebay... about 10 quid.
    Sweet thanks will look for one. Ta

  8. #7
    evomaster3000's Avatar
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    Ok so i've now got an OBD2 and Vag com software (free limited ross tech version)

    Managed to get 3 codes up, can't remember exact but here's the jist.

    One was 17978 MAF - i know what this was, inlet to turbo works it's way loose sometimes and i get no power atall! has happened twice in recent weeks, boost hoses have blown once or twice too.

    and two relating to boost control 00553 and another one very similar, basicially saying control difference.

    I checked them up and one consistent thing was N75 and turbo, well i've just de-coked the turbo and it's all ok, so i'm assuming my N75 is faulty.

    Been driving it hard lately to "make" the N75 correct the boost when i accelerate, doesn't seem to happen much, sits at between 18 and 22psi depending on revs.

    If i hold it on motorway at this pressure it will go in to limp.

    Although i plan on bigger injectors and a gt1749, I need it to work as it should at the moment.

    I have played with the VNT actuator adjustment to get an adequate boost at rpm (not too high) but not too much lag.

    Anyone know what vw/audi charge for new N75 i've heard 38 and 88?

  9. #8
    TDI

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    You souldn't be messing with actuator. This is factory calibrated setting. If you get overboost more than likely you got sticky vanes or if they been cleaned maybe driving ring is wrong way around. N75 is also common problem an quite expensive 80 from dealer. If you need one i get them for cheaper but you'll have to wait a while (usually a week).
    Professional chiptuning (most makes and models) and diagnostics (VAG, BMW, Vauxhall).

  10. #9
    evomaster3000's Avatar
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    Just ordered a new N75 - the later version with a new plug too as this is 1/2 the price and the same part, just different plug, they even told me the new part superceeds the old one so it'll work.

  11. #10
    evomaster3000's Avatar
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    Problem now sorted, cost 40.56 from Dealer, and spent yesterday re-calibrating the turbo actuator for correct boost, now i think it's sorted thank god, i can now enjoy full throttle performance without the risk of killing my turbo, blowing boost hoses and going in to limp mode.

 

 

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