boost creep from nowhere

Discussion in 'Technical' started by r5bakakas, Sep 20, 2015.

  1. r5bakakas

    r5bakakas Member

    Hello from Greece. Long story short, Vg30det, single turbo pte 5857, tomei poncams, chipped ecu, sard 880, tial 38mm external wastegate. Got the turbo off for rebuilt and tha car sat as is for almost 5 months. Putted then the rebuilted turbo and from then the car suffers from an unexplained boost creep. The car builts 10 psi of boost as it did before. But now after 6k rpm the boost start rising and i have the feeling that it wont stop. When this happens the car starts leaning out and if i push it it will go to 17 18 af. Nothing changed except rebuilted turbo.
    Already checked wastegate, cam timing, fuel pump, fuel regulator, fuel injectors and the turbo itself. Any thoughts?
  2. Fists

    Fists Well-Known Member

    38mm is a bit small for a 3L isn't it? Maybe now that your turbo is running smoothly the gate can't keep up?
  3. r5bakakas

    r5bakakas Member

    But there was no problem before for the wastegate to control the pressure even with the turbo brand new.
    The problem is somewhere else but I can't spot it. Maybe the too lean condition produces hot gasses that the turbo can't handle.
  4. badxtc

    badxtc kirby's bitch

    Yasou megale cheak you acuator air hose the line that gose there may have a hole in it. . Or just change them. Altogether.
  5. bRACKET

    bRACKET Do Right Dean

    Yes 38mm too small, 45mm is the smallest I would run on a 3L, 50mm even better. All depends on boost levels though. Big turbo with a low boost needs a much bigger gate than a smaller turbo at high boost.

    As has been said, double check the actuator line and make sure you've plumbed it into the correct port on the gate. Do you have a boost controller or just running it off spring pressure?
  6. tassuperkart

    tassuperkart Its a lie I tell you!

    Hes never had any problem withit in the past so the 'gate is working.
    Compare it with the stock internal flap gate and 38mm is getting mighty big.

    Assuming the manifold pressure line isnt leaking as badxtc suggests then Id say after a long period of not being used the gate is rusted/sticking and not opening fully.

    This often happens with stock flap style 'gates driven around town that rarely see gated boost pressure and the flapper shaft rusts up and sticks.
    Ive had one stick open in the past.

  7. r5bakakas

    r5bakakas Member

    I changed the wastegate line with a new one straight from the turbo to boost control or bleed valve.
    The wastegate came out and tested outside and it works as new. No rust or stuck piston. Any other thought?
  8. Fists

    Fists Well-Known Member

    That's basically it unless it's possible you've got a rag stuck down the wastegate outlet before it meets the rest of the system. Either you aren't getting full pressure signal to the gate or your gate/exhaust isn't flowing enough bypass air.
  9. SuperZ

    SuperZ Resident Z lunatic

  10. tassuperkart

    tassuperkart Its a lie I tell you!

    Ummmmmm... *scratches head* got me buggered!!!!

  11. SuperZ

    SuperZ Resident Z lunatic

    Actuator related - but you state they have been tested and so the rod/ spring relief/ spring must be working fine.

    This means you have a hole or loose clamp somewhere between the actuator / boost line / Vacuum line or the actuator T- Piece. (If you still have them attached)

    A vacuum/ loss of pressure introduced into the actuator line means more pressure being lost and this means boost creep as the waste gates lose pressure and close under more pressure.

    The more pressure or boost the greater the hole/ vacuum - and this is why it has the "creeping phenomenom that gives it its namesake"

    Check your lines and clamps
  12. r5bakakas

    r5bakakas Member

    As I said in a previous post the wastegate vacuum line is new and direct from the turbo to the wastegate. I made many boost leak tests and there is no leak. I believe it's not wastegate related. Yesterday I took a look with the consult but couldn't try it on the road cause it was raining. The only strange I saw is that the ecu power is little low. 10.2 to 11.8 Max with the car running. I lol take a look at one of my older logs to see the volts there as I remember that I had 13-14v before. If this is true then it might be a grounding issue.
  13. tassuperkart

    tassuperkart Its a lie I tell you!

    That is a lot low!
    Sort that out and then see what happens.
  14. SuperZ

    SuperZ Resident Z lunatic

    Was thinking maybe loose clamps

    Sorry - lost me - I don't know what else causes boost creep other than an actuator issue - I guess the ECU signal through to the stock safety boost solenoids could do this though since it affects the actuators

    ECU sounds low

  15. SuperZ

    SuperZ Resident Z lunatic

    Want to run this by you.....I'm not an expert in this....but this does not add up!

    How can you get boost creep that's not actuator/ waste-gate related?

    The only control signal from the ECU that correlates to an actuator/waste gate related boost creep is the Safety Boost Solenoids and the Detonation Sensor.

    If the signal is on or off to the safety solenoids this still will not cause boost creep as they are both still working together unless one of the actuators is faulty or not set correctly

    To get boost creep from a ECU signal to the solenoid - would have to mean only one solenoid is working? - in this instance only one waste gate is closing while one is opening.

    This would give you boost creep and/or spike if one is working to safety boost and the other to max boost as one is now cutting in/ out earlier than the other - they are now fighting each other and creep is felt as a result

    But this would activated the det sensor and throw a Code 34 which you haven't mentioned! (You haven't mentioned bypassing the det sensor either)

    Given you say the ECU is shorting and you don't have a faulty densor code - Surely this means it can only be a short in the solenoid or solenoid line to the ECU? Can you disconnect the solenoids (and test only for creep).... just to confirm - ECU should come on with good voltage instantly if that's the case otherwise its has to be the solenoid to ECU wire? :confused:

    Not an expert here - this is out of my pay grade and just doesn't make sense there something else you haven't told us..........?


  16. stumagoo

    stumagoo Active Member

    I was actually wondering if he had used one of the original boost lines with the restrictor in it before, that is one way it may have been effected by a new line to the actuator
  17. SuperZ

    SuperZ Resident Z lunatic

    The pressure would still be the same unless he used one line in that case or one that's deficient in a restrictor as there's two per line - There are marker lines indicating where they are.

    There's something he hasn't told us..............LOL ;)

    Maybe this is a cryptic aus300zx trolling line expedition......:rofl:

    Maybe a faulty solenoid and a faulty det sensor :p

    The poor Z must be in a real state of affairs........:nono:



    Last edited: Sep 26, 2015
  18. tassuperkart

    tassuperkart Its a lie I tell you!

    LOL. Its not zed!
    Its an S13 with a VG30det!!!!! Single turbo.
    DET's dont have a det sensor.
    Pays to read the thread thoroughly man!!!!!
  19. r5bakakas

    r5bakakas Member

    I use z32 ecu-wiring loom so i have a det sensor. But i dont use any of the original actuators or lines. never used them so its not the case. Any way the ecu has no error codes and everything looks ok at the consult. Except the low voltage as i said before. I'll try to get a good voltage to the ecu first and then try again at the road. I took a look at the grounds yesterday but everithing is fine there. I found some corrosion at the front fuse box where the ecu relay is. Didnt managed to fix it yet. Thats the next step and we will see.
  20. kickerzx

    kickerzx Member

    Is it possible you have fiddled with the CAS and the engine are running alot less timing than usual? Its a long shot but late timing tends to spool turbos.

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