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Found the source of boost problem.......

Discussion in 'A4/S4 forum(B5 Chassis)' started by neilA4, May 1, 2010.

  1. neilA4
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    neilA4 Member

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    [May 1, 2010]
    found the rattle...
    [​IMG]

    looks like it's been like that for a while, housing also looks like it has got hot too!

    [​IMG]

    sp51r is on, overboosting a bit (well a lot) need to adjust actuator:icon_thumright: methinks, should be able to get to it by dismantling the forge item whilst still on car (fingers crossed!)
    #1
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  3. Matt82
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    Matt82 Active Member

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    [May 1, 2010]
    what am i looking at ?/
    #2
  4. SteVR
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    SteVR Member

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    [May 1, 2010]
    The waste gate flap.
    #3
  5. Matt82
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    Matt82 Active Member

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    [May 1, 2010]
    aaaaaaaaaaaah
    #4
  6. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [May 1, 2010]
    you were lucky to get ANY boost with a fully floating wastegate flapper.

    The actuator will be near impossible to to adjust with it ftted or at least with the manifold fitted.

    What PSI is the forge unit set at? As an oem one is around 5-6 PSI iirc
    #5
  7. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [May 1, 2010]
    What map you running?

    What tells you that it's overboosting?
    #6
  8. Matt82
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    Matt82 Active Member

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    [May 1, 2010]
    why didnt the penny just drop out when the actuator opened? id have thought that would be chewed up by the turbine almost straight away
    #7
  9. neilA4
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    neilA4 Member

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    [May 1, 2010]
    Just standard managment for the moment, (although could be chipped for all I know!), forge actuator on weakest spring (7-10 psi), think i've put too much preload on it boost started to spike to 1.5 bar on full throttle was only that high for a split second then i backed off throttle may of gone higher if i kept pedal down lol.
    Just driving round today on halfish throttle to keep it under 1 bar, think 0.9 bar is the standard for 180bhp ajl engine?

    I picked up a actuator rod that was too short by a few mm so had to put about 3 turns of preload on it, thought it would be ok with the weakest spring, was going to get some threaded bar but looks like forge have used a 1/4 unf thread, not m6 like standard actuator so will have to wait till i'm at work will run a die down some .250" bar to make a longer rod.

    may put the standard actuator back on yet I dont want to be melting any pistons.

    looks like the car has not been boosting since i got it lol.
    #8
  10. neilA4
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    neilA4 Member

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    [May 1, 2010]
    actuator would not have seen any boost to open with the penny valve rattling away!

    it was a very loud rattle that was getting louder and very annoying!
    #9
  11. B5_Avant_AAN_Powered
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    B5_Avant_AAN_Powered Member

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    [May 1, 2010]
    normally when i set customers cars up ( im a Ford and Cosworth tuning therapist here so dont kill me please lads!)
    the rule of thumb is when setting pre-load, with wastegate arm closed fully, adjust wastegate rod to when imagine looking down onto the wastegate arm , the actuator rod would eclipse the arm by half, like an eclipse lol

    hard to describe but i know what i mean ;) and am sure you do too :D

    semi circles elipsed....... erm, half and half showing...... erm..... ****........ erm........ ;)
    #10
  12. Matt82
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    Matt82 Active Member

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    [May 2, 2010]
    on throttle, off throttle, hot, cold or all the time?

    i was thinking in terms of s4. one n75 controlling boost so if one penny fell off the other turbo would still make boost etc

    #11
  13. Fraser
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    Fraser Member

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    [May 2, 2010]
    same happened to mine, i slotted in a new turbo as the repair was uneconomical, wastegate arm snapped, penny missing etc
    #12
  14. Oranoco
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    Oranoco Well-Known Member

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    [May 2, 2010]
    Who and where? Are you on www.passionford.com?
    #13
  15. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 2, 2010]
    On mine the wastegate preload pushed the penny THRU the turbine housing, and the penny itself dropped into the turbine port inside the turbine manifold. Luckily the hole is too small for it to fit down, so it just stayed there, and the car continued working, making 0psi and having about 100hp.

    It was rattling for a long time, only on the overrun, before it finally failed, rattle vanished along with the power.

    The ECU would have just shut down the fuel had you kept the toe in, it doesnt have boost sensing, but the MAF value would have quickly gone out of range. The stock actuator runs at around 4-5psi and the ECU uses the N75 to create the boost curve that it wants. Wedging in a 10psi spring isnt going to make the ECU very happy i dont think.
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  16. neilA4
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    neilA4 Member

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    [May 2, 2010]
    just looked on the forge website, the spring is rated 5 to 10 psi. I have now ajusted actuator to half a turn of preload, had to take turbo off in the end didn't take as long as yesterday.

    In 2nd gear it overboosts to 1.2 bar then settles at 1 bar. In third it overboosted to 1.5 bar and held for a while then I backed off throttle.

    If boost is high and the ecu cuts the fuel wouldn't it run dangerously lean?

    The standard actuator seems just as hard to pull as the forge item. May have to try putting that on next, although I had a forge actuator on my old calibra turbo which did go weak after a while. or I can try and source a weaker spring, but this is the weakest that forge advertise, unless I have a dodgy spring lol, if their spring is rated to 10 psi and it's running at 20 ish psi then someting is wrong somewhere, will do vag com code check in a min.

    cheers.
    #15
  17. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 2, 2010]
    Well it cuts all fuel, and probably spark too, so its not lean its just not combusting anymore...

    The point is that the N75 valve is driven by a map on the ECU to bleed a certain % of boost in order to generate say 1 bar. If you fit a actuator with higher pressure, and still bleed the same amount of boost, the net result is that you will run more boost. The ECU will try to compensate, and will back off the N75 in order to get things back under control, but it can only do so much and so quickly, hence you end up with huge spikes and possibly fault codes and limp mode.
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  18. neilA4
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    neilA4 Member

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    [May 2, 2010]
    no fault codes yet, i'll try and get a weaker spring, or put the standard actuator on it. looks like n75 can't bleed off enough air then.

    car was very quick though!

    cheers
    #17
  19. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [May 2, 2010]
    Mine spikes 1.2 Bar on the STD map and does not hard cut at any time.

    It may be because i am continueing to use the OEM actuator and the ECU/N75 can deal with it fine.
    #18
  20. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 2, 2010]
    Neil, its not that the N75 cant bleed off too much air, its that the default map is bleeding off too much air, becuase its expecting the Actuator to open at 4psi not 10.
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  21. neilA4
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    neilA4 Member

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    [May 2, 2010]
    cheers guys.

    may as well put the standard actuator on, should only take 2 hrs this time lol. Turbo will have been on and off 3 times in as many days!!

    Another question, is the standard recierc dumpvalve supposed to be loudish? Not used to hearing it work tbh.

    cheers
    #20
  22. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 2, 2010]
    If you've got a cone filter or something on there, you'll get a bit of a tish thru it.
    #21
  23. neilA4
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    neilA4 Member

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    [May 2, 2010]
    nope don't like cone filters, just standard box for me. Dont think iv'e plumbed it in the wrong way round if that's possible?
    #22
  24. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 2, 2010]
    If your getting a tish with the stock airbox, are you sure the pipes on the DV are all tight?
    #23
  25. neilA4
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    neilA4 Member

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    [May 2, 2010]
    i'll go over everything tomorrow got to strip it all again lol
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  26. neilA4
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    neilA4 Member

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    [May 3, 2010]
    Right, standard k03-005 actuator fitted with half turn of preload, so at full throttle on the accelerator pedal I get-

    1st gear- 0.5 bar max boost

    2nd gear- 1.2 bar overboost trailing off to 0.9-1.0bar in higher revs

    3rd gear - 1.5 bar overboost then holding 1.2-1.3 bar

    4th gear- same as third

    in 3rd and 4th felt like there were a few flat spots.

    cheers
    #25
  27. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 3, 2010]
    Whats your peak MAF readings, and lambda adaption values on vagcom?

    I'm wondering if you've got a bit of a lazy MAF, thats pushing the turbo further than normal?
    #26
  28. neilA4
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    neilA4 Member

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    [May 3, 2010]
    not done any logging before. which blocks do I need to log? How do I identify the data?, or do I click log just before a 1-2-3-4 gear run?

    i have a registered version of vagcom 409.1-s and a gendan ODB 2 lead if that will support logging?

    cheers.
    #27
  29. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 3, 2010]
    should do.

    Basically you want to open the engine controller, then measuring blocks, then have a flick thru. You can just have a cursory glance over the lambda values (they're up around the 30's), make a note and post them up. Then find a block that shows MAF (003 will probably suffice) and press the log button.

    It pops up a little thing saying "Start" so what i'd do is get the car moving at say 2000rpm in 3rd, click start, then floor it right thru the revs, then you can click "Stop", can always slow down and do it again if you wish, or leave it running, but it gets rather difficult to see whats going on if the log is 5 minutes long, rather than 10 seconds.
    #28
  30. neilA4
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    neilA4 Member

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    [May 3, 2010]
    doh it throws a wobbly when i start the engine, this is on an old laptop. Interface not found or something.

    Would try my newer one but the battery won't last more than a couple of minutes!! I'll get a new battery and report back later in the week.

    cheers
    #29
  31. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 3, 2010]
    try connecting the cable after the engine has started?
    #30
  32. neilA4
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    neilA4 Member

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    [May 3, 2010]
    just seems to freeze up!! laptop is using usb1 it's that old
    #31
  33. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 3, 2010]
    Shouldnt really matter though, quite a few people use ancient laptops for vagcom, save their shiney ones getting knocked about.
    #32
  34. neilA4
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    neilA4 Member

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    [May 3, 2010]
    ahhh, i'm using a serial version of vagcom with a usb lead will have to play with a few things methinks
    #33
  35. neilA4
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    neilA4 Member

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    [May 4, 2010]
    Right, vacom working well now, tried 3rd gear as you said, boost went up to 1.5bar and then hit boost cut (poo pants time lol)
    so, tried 2nd gear run as below, ot sure about lambda tbh but it was -3 -4ish all the time.
    [​IMG]

    and 3rd gear with boost cut, made boost v quick
    [​IMG]

    could it be faulty n75? I only make 0.5bar in 1st gear full throttle?

    cheers
    #34
  36. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 4, 2010]
    in 1st gear theres just not enough load on the engine to make proper boost. Your peak MAF value there is 188g/s which is something like 230hp.

    Try unplugging the N75 valve, and see what boost you make then. It should give you about 4psi.
    #35
  37. neilA4
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    neilA4 Member

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    [May 4, 2010]
    Will try tomorrow, also have a spare n75 to try, but it's an older version. Will do some more logging and try 1st, 2nd, 3rd together.

    cheers
    #36
  38. neilA4
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    neilA4 Member

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    [May 5, 2010]
    Changed the n75 over, still the same, maybee a little smoother.

    Unplugged the n75, get 0.3ish bar boost max.

    what symptoms would a sticking recirc valve cause? Can't hear it now (since putting the standard actuator back on).

    both n75 valves had part number 058906283 c, etka lists 058906283 f , it that would make any differance?


    cheers
    Last edited: May 5, 2010
    #37
  39. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [May 5, 2010]
    F is the new part number as it superceeded the C.

    Is it still overboosting with the std actuator on?

    My car is happy as a sand boy overboosting,our ECUs are a little dumb so it doesn't notice as we have no Map sensors


    Boost is only generated when an engine sees load, in 1st unless you are towing, or climbing a stupid hill, you won't generate much load.
    #38
  40. neilA4
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    neilA4 Member

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    [May 5, 2010]
    yes it's still overboosting with standard actuator, it's not too bad if i start in 2nd at low revs and go throught the gears, this other n75 seems to bring it back down to 1.0bar ish in the higher revs.

    just done a log in 2nd to 3rd gear, revs didn't register but i took it to middle of redline, can tell when i changed gear due to maf value. not sure what i've logged. It seems like the turbo can genegrate boost faster than the ecu can manage it. If i'm in 3rd around 3000rpm and boot it the boost is immediatly up to 1.5bar and i back off throttle!

    [​IMG]
    #39
  41. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 5, 2010]
    If the cars remapped it might be a combination of an overzealous map pushing the N75 duty cycle right up in an attempt to get the turbo spooling quicker, plus the scroll turbo spooling up quicker and more aggressively, causing the boost to build so quickly the ECU shuts it down, thinking there is a fault.
    #40

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