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2009-2014 Cadillac CTS-V Performance Mods Discussion, P-valve Question in Cadillac CTS-V Series Forum - 2009-2014; I'm new too. On ls1tech Jesse said my car has an issue, he said I'm loosing 30 rwhp, as well ...
  1. #61
    Domsz06 is offline Cadillac Owner
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    Re: P-valve Question

    I'm new too. On ls1tech Jesse said my car has an issue, he said I'm loosing 30 rwhp, as well as bleeding boost. My car is CURRENTLY stock. So he mentioned there was a screw I needed to make sure it was not keeping the flap or something from allowing full boost.

    Back to your over boost, yes there is an overboost turn off in the comp when you tune, however it appears that GM made another fail safe that is a physical device, that needs to be over ridden or else it won't allow full boost WHEN i put my 9.5 pulley in.

    Thanks everyone.

    http://www.ls1tech.com/forums/13955152-post7.html

    here is the post.

  2. #62
    GMX322V S/C's Avatar
    GMX322V S/C is offline Cadillac Owners Connoisseur
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    Re: P-valve Question

    Here's a simplfied diagram I posted awhile ago that indicates the letter labels:



    When the Boost Bypass Valve is closed, the SC can build boost normally. Above about 12 PSI, the ECM kicks in a failsafe and opens the valve to bleed boost. In order to build boost above 12 PSI, you have to override the failsafe by disconnecting the Boost Control Solenoid from the Bypass Valve Actuator.

  3. #63
    PhxTriode is offline Cadillac Owner
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    I find this post interesting. I have hit 13.5psi (on the Dyno) and never have done anything to my P-Valve

  4. #64
    Domsz06 is offline Cadillac Owner
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    Re: P-valve Question

    Phx....

    Intersting. Perhaps the computer elimated it still is true... Idk...

    I still need to find that screw...

  5. #65
    PhxTriode is offline Cadillac Owner
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    Re: P-valve Question

    I think it is referring to a set screw that is on the shaft of the bypass butterfly that is adjusted to give a 'Home' or closed position. Kind of like a idle adjustment screw for a carburetor.

  6. #66
    Domsz06 is offline Cadillac Owner
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    Re: P-valve Question

    Quote Originally Posted by PhxTriode View Post
    I think it is referring to a set screw that is on the shaft of the bypass butterfly that is adjusted to give a 'Home' or closed position. Kind of like a idle adjustment screw for a carburetor.
    That's what I thought, just wondering where and how to tell......

  7. #67
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    Re: P-valve Question

    delete

  8. #68
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    Re: P-valve Question

    Hey guys, referring to the picture I attached (from above), I was wondering if anybody has the answers to my questions below:

    1. If we disable the boost control solenoid from controlling the bypass valve actuator and remain using the stock pulley, can we see higher boost?

    By removiong line P/O we completely remove the control of the actuator from the solenoid, and the same can be done by removing the line X, which is the boost/vacuum source. Either will achieve the same result, but I personally removed the P/O line on mine. I am not seeing much boost above 9psi (digital readout from manifold absolute pressure sensor, MAP, on my interceptor).

    2. There must be different areas of boost throughout the intake manifold, supercharger and heads so which sensor is a better indicator of actual "boost" pressure as defined by a tuner?

    3. I would like to boost 10-12psi so can I do this on the stock pulley?

    I am trying to avoid removing the upper blower pulley as that is pressed on. The lower pulley looks like a PITA (even with my 18V snap-on electric impact gun) too so I would like to avoid that. I just want a few more PSI and feel it's achievable with just a little work. Thanks for the input guys.
    Attached Images

  9. #69
    Da V-Man is offline Cadillac Owners Fanatic
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    Re: P-valve Question

    Quote Originally Posted by HUGN*RDS View Post
    Hey guys, referring to the picture I attached (from above), I was wondering if anybody has the answers to my questions below:

    1. If we disable the boost control solenoid from controlling the bypass valve actuator and remain using the stock pulley, can we see higher boost?

    By removiong line P/O we completely remove the control of the actuator from the solenoid, and the same can be done by removing the line X, which is the boost/vacuum source. Either will achieve the same result, but I personally removed the P/O line on mine. I am not seeing much boost above 9psi (digital readout from manifold absolute pressure sensor, MAP, on my interceptor).

    2. There must be different areas of boost throughout the intake manifold, supercharger and heads so which sensor is a better indicator of actual "boost" pressure as defined by a tuner?

    3. I would like to boost 10-12psi so can I do this on the stock pulley?

    I am trying to avoid removing the upper blower pulley as that is pressed on. The lower pulley looks like a PITA (even with my 18V snap-on electric impact gun) too so I would like to avoid that. I just want a few more PSI and feel it's achievable with just a little work. Thanks for the input guys.
    First off, that diagram is wrong. The X line should tie into the intake plenum. The boost control solenoid feeds boost to the bypass valve actuator. There is no boost upstream of the SC rotors.

    To answer your questions:
    1. No, not unless the bypass valve isn't fully seated.
    2. Not really. Just as water seeks its own level, pressurized air will equalize all chamber to which it has access (upstream of the intake valve).
    3. Nope, not unless you cause a restriction somewhere. You may be able to tweak it up slightly by opening the intake path, but no where near 11-12 psi.

    If you're concerned about the boost control solenoid opening too soon, just increase its actuation value in the tune. I would take that route and leave the plumbing alone.

  10. #70
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    Re: P-valve Question

    this thread in all honesty is a joke for the V comunity as it neither 'clearly' shows how to do it, as well as arguments of why it should be done.
    can anyone who has "successfully" bypassed this over boost subject please make a short you tube video of said mod? 5 pgs of garbage and no
    clear solution has been given. i can see the m5 forum guys coming here for a laugh.
    Tedboss1, Tedboss1 and gOt BoOsT like this.

  11. #71
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    Re: P-valve Question

    Quote Originally Posted by Da V-Man View Post
    First off, that diagram is wrong. The X line should tie into the intake plenum. The boost control solenoid feeds boost to the bypass valve actuator. There is no boost upstream of the SC rotors.

    To answer your questions:
    1. No, not unless the bypass valve isn't fully seated.
    2. Not really. Just as water seeks its own level, pressurized air will equalize all chamber to which it has access (upstream of the intake valve).
    3. Nope, not unless you cause a restriction somewhere. You may be able to tweak it up slightly by opening the intake path, but no where near 11-12 psi.

    If you're concerned about the boost control solenoid opening too soon, just increase its actuation value in the tune. I would take that route and leave the plumbing alone.
    I am aware of where the x line goes. There are two lines used for vac/boost in that system. I think they are on the manifold correct me if I am wrong. I think if I disabled the bypass valve it would be fully seated. We swap pulleys to gain more boost but is there a few more in the stock one? And I already have a D3 intake and my air duct modded, that should help. I have done this on a similar supercharged vehicle so I figured the same concept of the bypass valve operation at high rpm's would apply because our stock pulley is limited.

  12. #72
    Da V-Man is offline Cadillac Owners Fanatic
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    Re: P-valve Question

    The bypass valve is a spring-loaded, normally-closed valve. With the engine off, and if the set screw is adjusted properly, it will be fully seated. With the engine on and in low-load mode (idle, cruising, etc), manifold vacuum is applied to one side of the actuator diaphram, which pulls the bypass valve open. In high-load mode (boost), manifold vacuum goes away and the valve closes. If the boost level exceeds what's programmed in the tune (about +12#), boost is then fed from the boost control solenoid to the other side of the actuator diaphram, which pushes the bypass valve open. The stock pulley is good for about 9# of boost, nowhere near the programmed limit for the boost control solenoid. If the bypass valve is operating correctly, you will not get any more boost from the SC unless you spin it faster. Bottom line: disabling a correctly-functioning bypass valve will not allow you to build more boost. What it may do is build boost a little faster. And you will always be compressing air through the SC, which may require tweaking the tune.

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