Can't turn boost down

Posted by jdm9221, May 17, 2017

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  1. jdm9221

    jdm9221 Proven Member

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    I have a 97 eclipse GSX 16g,550cc injectors,walbro 255,hallman mbc, and a few other bolt ons. So I have the boost controller between the j pipe and and wastegate(yes it's hooked up right,and I've tried both ways). Before I was only hitting 13psi because it was leaking from my bov, replaced that(recirculated to the intake) and now it's hitting 26psi with the boost controller turned all the way down. Also on a side note I've been trying to set a base tune using my safc2 and my wideband. Hi throttle points are set -37 all the way across and it's still running 9.6 under boost, does this seem right to keep going lower considering they're only 550s and the safc maxes to -50? Any help is appreciated
     

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  2. Drop Top Road Trip

    Drop Top Road Trip Proven Member

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    Your MBC, is it a hardware store built piece? If so, does it have the little hole drilled in it? I recently installed a home built MBC and followed the instruction, drilling the little pressure relief hole...and the hole renders the MBC useless. All the boost pressure that would be transferred to the waste gate actuator just leaks out the hole.
     
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  3. jdm9221

    jdm9221 Proven Member

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    Nope. Hallman pro boost controller. It does have the vent hole but that's part of the design straight from hallman
     
    My DSM:
    1997 Mitsubishi Eclipse GSX

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    16g   manual
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  4. Drop Top Road Trip

    Drop Top Road Trip Proven Member

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    I can't understand how a boost controller with a built in leak can work. Logic says it just can't, but maybe someone with some engineering experience can explain it. Mine had me spiking to more than 20psi under any and all adjustments (pegging my boost gauge) so I removed it immediately.
     
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    1999 Mitsubishi Eclipse Spyder GST

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  5. jdm9221

    jdm9221 Proven Member

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    I bought it used from a friend but it worked when it was on his. My guess is the MBC itself or the wastegate stuck but I'm open to other opinions. Also hoping someone can answer my safc question. It seems crazy to be taking out 37% on 550s and still run rich
     
    My DSM:
    1997 Mitsubishi Eclipse GSX

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  6. livedsm4g63

    livedsm4g63 Proven Member

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    Your understanding isnt far off. When you build up pressure the excess pressure needs to leak. How else could you hold steady pressure? If there was no leak, you would spike to as much pressure as the turbo could make (or system could take) until something let go.

    I would uninstall your mbc and open it up all the way. Blow into the mbc from the bottom side, where the boost would go in to. If you can feel air coming out the other side, more then likely it is working. I would still open it up to inspect the internals. Worst case, remove it from the system and see if the problem still occurs. If it does its the wastegate or flapper. Normally when you get boost spiking it is in reference to the wastegate not opening. Be it stuck, or a mbc limiting the usage or range of motion. Double check that to be sure. Hope this helps a little.
     
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  7. jdm9221

    jdm9221 Proven Member

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    Could my bov set screw need adjusted? If the bov is letting it go it would hold high boost right? I had the problem after I installed the bov and mbc. Whenever I'm in boost and let off I get super loud turbo flutter sounds
     
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    1997 Mitsubishi Eclipse GSX

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  8. livedsm4g63

    livedsm4g63 Proven Member

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    This would cause a surging issue. The bov doesnt limit the amount of boost you see. It releases the pressure you've already placed into the system. Sounds like there may be multiple issues.
     
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    1991 Eagle Talon TSi AWD

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  9. jdm9221

    jdm9221 Proven Member

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    a good friend who knows all about these set the bov set screw for me so I would assume it's fine. I just can't figure out why it's overboosting. It's either stock wastegate 13psi with no mbc or I put the mbc on and I'm stuck open at 26
     
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    1997 Mitsubishi Eclipse GSX

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  10. livedsm4g63

    livedsm4g63 Proven Member

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    Well if your stock wastegate is working as intended (13psi) and the wastegate is not allowing you to limit the boost, this would point to either a blockage in the vacuum lines or a defective mbc.
     
    My DSM:
    1991 Eagle Talon TSi AWD

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  11. jdm9221

    jdm9221 Proven Member

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    I just ran all new vacuum lines when I put the vacuum line nipple in for the j pipe yesterday
     
    My DSM:
    1997 Mitsubishi Eclipse GSX

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  12. 91talonts1

    91talonts1 Proven Member

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    The fitting with the vent hole on the right port?
     
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  13. gofer

    gofer Moderator

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    Lets go back to your original post...
    You answered your own question in your post, before you were hitting 13psi because you had a leak at your bov. The leak at your bov was, in a round about way, acting as a boost controller which is why you were able to maintain 13psi so the instant you replaced it your system relies on the wastegate to control boost, i.e., the amount of exhaust gas that flows over the turbine to increase/decrease the amount of pressure the turbo will spool to.

    Were you ever able to hit 13psi after the bov replacement?
    I'm guessing you have an aftermarket downpipe/exhaust system?​

    My recommendation is to check if you're experiencing boost creep by removing the wastegate actuator (wga) arm from the flapper on the hotside of the turbo. Just pull the grenade pin and slide the arm off of it then go for a drive, if it builds 13psi without the wga installed its boost creep. To reinstall you'll have to pull straight out on the wga arm (it's under tension) and extend it out to the flapper. On a properly functioning turbo exhaust waste setup you should build 0psi even at WOT with the wga removed.


    If you're suffering from boost creep the only way to fix it is...
    - Install a stock dp/cat (assuming you don't have them).
    - Port the turbo hotside, specifically the inlet into the wastage flapper. This is why 16g setups suffer from boost creep, the exhaust gas has to take a 90* turn to exit out the wastegate port which creates turbulence/high pressure zone so it's easier for the exhaust gas to go through the turbine wheel which causes your uncontrollable boost pressure.
    - Build your setup to run 26psi by going to meth. inj./E85.
    Here's a good image the JusMX posted about porting the hotside if you go that route.

    5579840020_large.jpg

    While you're in there it doesn't hurt to port the o2 housing wastegate port outlet either which helps the exhaust transition back into the stream without creating turbulence or high pressure there.

    o2-outlet.jpg



     
    My DSM:
    1997 Mitsubishi Eclipse GST

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  14. jdm9221

    jdm9221 Proven Member

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    Goes from the wastegate to the vented hole side, other side to my j pipe
     
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  15. jdm9221

    jdm9221 Proven Member

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    I've never had boost creep. I also installed the boost controller and bov at the same time. I'm going to take out the boost controller and see what it hits rn
     
    My DSM:
    1997 Mitsubishi Eclipse GSX

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  16. doubleclutch

    doubleclutch Supporting Member

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    Did you even read gofer's post? maybe you didn't have boost creep because the turbo couldn't keep up with the massive boost leak generated by the BOV.

    Can you tell us if your 16g has been ported? What exhaust are you using?
     
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  17. jdm9221

    jdm9221 Proven Member

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    It's a non port 16 and a thermal exhaust. Even at 26 there's no boost creep
     
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    1997 Mitsubishi Eclipse GSX

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  18. gofer

    gofer Moderator

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    You're not understanding the concept of boost creep, bud.

    If you're hitting 26psi and trying to run wastegate pressure at 13psi then it's creeping 13psi, whether that's because you're wastegate isn't efficient enough or it's because of a faulty boost controller that's what you're going to have to troubleshoot.
     
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    1997 Mitsubishi Eclipse GST

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  19. jdm9221

    jdm9221 Proven Member

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    I'm not trying to run wastegate pressure tho, That's why I bought the mbc. I'm trying to set it to 19 pounds. If I run a straight line from j pipe to wastegate it obviously runs 13psi. If I throw the mbc between it then I can't change it other than 26. If my wastegate was the problem it would overboost without the boost controller in the equation
     
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    1997 Mitsubishi Eclipse GSX

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  20. gofer

    gofer Moderator

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    If your boost controller is turned all the way down then you're trying to run wastegate pressure... :thumb:

    Literally an hour ago (post #15) you said you were going to pull the mbc and see what happened, then never came in and updated the thread with your result.

    Untitled.jpg
     
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    1997 Mitsubishi Eclipse GST

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  21. jdm9221

    jdm9221 Proven Member

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    I said it wasn't wastegate pressure because I thought the boost controller was at fault:thumb: I took the boost controller out of the equation and it's still at 26 so now how do I go about fixing my wastegate
     
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    1997 Mitsubishi Eclipse GSX

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  22. Eddie Tsi

    Eddie Tsi Proven Member

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    Check to see if the waste gate flapper move freely with wga arm removed. (Could be a stuck flapper) Next check the actuator itself by pumping compressed air (13~15psi)through vacuum line to the actuator.The arm should move at 13 psi if the spring rate is 13 psi. Check for leaks if the valve/arm doesn't move. If both are in working order, it could be creep like gofer stated.
     
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  23. gofer

    gofer Moderator

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    Read the entire post I made above, it tells you how to troubleshoot it in detail by just pulling the cotter pin off the wga flapper, pulling the wga arm off, then going for a drive.
     
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  24. pauleyman

    pauleyman DSM Wiseman

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    Wg pressure also is probably not 13. A stock actuator is like 9psi all by itself.
     
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  25. PlanZero

    PlanZero Proven Member

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    You don't mention any exhaust mods in your profile, so I doubt it's boost creep. 16gs are notorious for creep on a 3" catless exhaust, the usual fix being porting as gofer mentioned and/or a tubular O2 housing (02 dumps rarely help). I'm betting on the WG.
    You definitely have something going on with your safc as 550s in a 2g should require very little adjustment. Make sure you don't have any boost leaks as they will make you run rich. You may want to invest in a afpr as some people have problems with a 255 over running the stock fpr.
    http://www.roadraceengineering.com/newafc.htm
     
    My DSM:
    1996 Mitsubishi Eclipse Spyder GST

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    1996 Eagle Talon TSi

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