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Boost controller not working properly

Posted by Brad Bell, Aug 23, 2018

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  1. Brad Bell

    Brad Bell Proven Member

    179
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    Joined Aug 15, 2014
    Levant, Maine
    I know there is probably a thousand manual boost controller troubleshooting threads out there. But none of them have helped with my situation. Running 420a turbo. I have this ball and spring manual boost controller running between the nipple coming out of my turbo and the wastegate. However between the wastegate and the boost controller, I have a 'T' fitting that runs a vacuum line to my fuel pressure regulator. Stock wastegate spring on my turbo is 8psi, but with the boost controller installed and the screw loosened as much as possible without coming off it's boosting well over 10psi. Not sure what's wrong, tripple checked to make sure controller is installed correctly.
    Thanks guys.
     

    Street Build 335  9

    1999 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  2. Macgyver'sDSM

    Macgyver'sDSM Proven Member

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    On the lake, Wisconsin
    Yes you loosen the knob and boost goes up. Are you trying to lower boost? The only way to accomplish that in to install a lighter spring. Also you should not have tee there for your fuel pressure regulator. Find a nice vacuum source on the intake or throttle body for your fuel pressure regulator.
     

    Street Build 2K  10

    1995 Eagle Talon TSi
    awd · manual · 2G DSM
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  3. asexton6969

    asexton6969 Proven Member

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    Joined Nov 8, 2002
    Cedar Rapids, Iowa
    According to your DSM profile and Hahn's website, the 10 PSI spring is the factory standard. I see options for a 5 PSI spring or a 15 PSI spring. I would say everything is working correctly. If you want to lower boost you are gonna have to order the 5 PSI spring and adjust your boost controller from there.

    Reading further it appears there is more than one internal wastegate option. The information I posted above is for the modular wastegate actuator for the Super 16g/20g setups. I guess this would depend on what wastegate you have since there is more than one.

    I would try to locate a different source as I prefer not to tap in to my FPR line.
     

    Street Build 2K  0

    1998 Mitsubishi Eclipse GSX
    450 whp · 368 lb/ft · 2G DSM
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  4. Tyeler18

    Tyeler18 Proven Member

    2,058
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    Joined Dec 16, 2008
    Casa Grande, Arizona

    Drag Race Build 475  1

    1991 Eagle Talon TSi AWD
    awd · automatic · 1G DSM

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    1990 Eagle Talon TSi AWD
    manual · 1G DSM

    Autocross Build 744  0

    1998 Mitsubishi Eclipse GSX
    manual · 2G DSM

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    1991 Mitsubishi Galant VR-4
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  5. Brad Bell

    Brad Bell Proven Member

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    Joined Aug 15, 2014
    Levant, Maine
    Thank you guys for replying. Firstly by the instructions that came with the controller, turning the screw counterclockwise lowers boost, and clockwise raises it. I included a diagram of the boost controller I'm running, it's a NXS Motorsports MBC. Without a controller attached I'm running 8psi, I want to run 10psi but currently the controller goes past 10psi (I have to stop it from overboosting with the throttle). This is with the screw turned counterclockwise all the way, just before it comes out, only a few threads holding it on. Is it true that a boost controller can lower boost setting below what you're internal wastegate is set to? Or is my lowest setting possible 8psi? Also the fuel regulator I'm running only works properly when tee'd off on the wastegate line because it is a rasing rate regulator, which rasies under boost only not vacuum. Unless it is normal to have the signal line on the intake manifold. I've tried this but the fuel pressure jumps around as it moves with the vacuum of the engine.
     

    Attached Files:

    Last edited: Aug 24, 2018

    Street Build 335  9

    1999 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  6. brian9397gsx

    brian9397gsx Proven Member

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    sioux city, Iowa
    You should have a dedicated boost source to that controller, most of those types have a hole in them to allow pressure to escape so that the waste gate will close again. That could be why your overboosting its probably bleeding off pressure before it makes it to the gate.
     
    brian9397gsx

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  7. Brad Bell

    Brad Bell Proven Member

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    Levant, Maine
    So should I just be running my fuel pressure regulator off the intake manifold? I removed the stock regulator.
     

    Street Build 335  9

    1999 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  8. randman2011

    randman2011 Proven Member

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    Indianapolis, Indiana
    You definitely want the FPR to see manifold pressure. It's purpose is to vary the fuel pressure according to the pressure at the head. Running the line from near the turbo is going to make it less consistent and running it from after a bleeder-type boost controller is going to give you wild fluctuations in fuel pressure. The line between the controller and the wastegate actuator is going to be at atmospheric pressure until the boost pressure is high enough to bypass the spring in the controller and pressurize that line, so at WOT full boost it will be fine but at partial throttle (positive boost but not peak boost) you're going to be running lean due to low fuel pressure. In vacuum you would be running rich.

    I understand that this is kind of a silly suggestion, but have you double-checked that the boost controller is installed in the correct orientation> They are directional and if you accidentally switch the input and output vacuum lines it won't work. Knowing how they are typically constructed I would expect a reversed controller to exhibit your exact symptoms where loosening the adjustment all the way is still going to give you a high boost level. The next most obvious issue would be a leak in the vacuum line anywhere between the boost nipple and the wastegate.

    To answer your earlier question, a manual boost controller can only raise pressure above what your wastegate provides. There is no way to lower boost pressure below that without either replacing the wastegate spring or the entire wastegate actuator, depending on the design. If you're seeing 8 psi on your wastegate, a boost controller will only allow you to set the boost at 8 psi or above.
     

    Street Build 599  1

    1998 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  9. Macgyver'sDSM

    Macgyver'sDSM Proven Member

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    On the lake, Wisconsin
    Take the boost controller off and blow in one end while adjusting the knob. Fully closed no air should pass through = 8 psi waste gate spring. Fully open easy to blow through = 10 or more psi varies could be 18 psi fully open idk.
     

    Street Build 2K  10

    1995 Eagle Talon TSi
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  10. Brad Bell

    Brad Bell Proven Member

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    Levant, Maine
    Alright I will try running the fpr on the manifold instead of on the boost line. However this means my fuel pressure will increase dramatically when just driving the car normally, or whenever the vacuum changes. The stock regulator is removed. When it was on the boost line, fuel pressure only increased under boost not vacuum. Is this okay? Thanks everyone for your replies.
     

    Street Build 335  9

    1999 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  11. Macgyver'sDSM

    Macgyver'sDSM Proven Member

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    Joined Feb 20, 2017
    On the lake, Wisconsin
    IIshot a quick vid of my car for you. Fuel pressure should not rise under vacuum. The terms 1 to 1 or 1 to 4 mean boost pressure the first number and fuel pressure the second number. 1 psi of boost will rise fuel pressure 4 psi 1-4 as an example. Having it teed off the manual boost controller it is not seeing all the boost and therefore not rising as much as it is intended to. So a question I have is have you ran the fpr by itself directly off the turbo and if so did it have the same problem? If not give it a shot. You should have the same problem as running it off the manifold. So than that brings up another problem. Why does it run good when it is unable to get a good reading. Are you running the recommended base fuel pressure and injector size required by hann for that turbo kit?
     

    Street Build 2K  10

    1995 Eagle Talon TSi
    awd · manual · 2G DSM
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  12. Brad Bell

    Brad Bell Proven Member

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    Joined Aug 15, 2014
    Levant, Maine
    Yes I understand the ratios and how they work with boost. However I tried running my fpr signal line running off the manifold, and the fuel pressure will move according to what the vacuum is. Currently I have it set to 20psi with 440cc injectors, however if I rev the engine in neutral the fuel pressure will spike up to 40 to 50psi because it moves with vacuum AND boost. Only if I have it connected to the boost/wastegate line will the fuel pressure only move with boost, because there is no vacuum there. But if it's connected to my boost/wastegate line my boost controller doesn't seem to work.
     
    Last edited: Aug 24, 2018

    Street Build 335  9

    1999 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  13. Dsm panda

    Dsm panda Proven Member

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    Franklin, Wisconsin
    You have it backwards tightening the MBC raises the boost level by tightening spring tension so more boost is required to open the wg actuator. (Hes using ball and spring not a bleeder.)
    I used the same MBC.
     

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    1991 Eagle Talon TSi
    327 whp · 307 lb/ft · 1G DSM

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    1990 Plymouth Laser RS Turbo
    fwd · manual · 1G DSM
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  14. pauleyman

    pauleyman DSM Wiseman

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    oklahoma city, Oklahoma
    This is not correct for a ball and spring unit.
     

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    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  15. Brad Bell

    Brad Bell Proven Member

    179
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    Joined Aug 15, 2014
    Levant, Maine
    Alright I rearranged my lines so it works now. My fuel pressure regulator signal line is running directly off the turbo compressor housing with no tee. With my wastegate line with boost controller running off an open port on the back on my manifold. Boost controller is now working. Thanks for your help everyone!
     

    Street Build 335  9

    1999 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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