P-valve Question
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2009-2014 Cadillac CTS-V Performance Mods Discussion, P-valve Question in Cadillac CTS-V Series Forum - 2009-2014; In another thread, kencav mentioned "capping" the p-valve as per Jesse's (W4M) suggestion. I understand that kencav does not want ...
  1. #1
    musclesbmf is offline Cadillac Owners Connoisseur
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    P-valve Question

    In another thread, kencav mentioned "capping" the p-valve as per Jesse's (W4M) suggestion. I understand that kencav does not want to give away any secrets that are not his own, and I'm good with that. I was hoping Jesse would chime in here and let us know what to do and what the benefit is.

    Jesse?

    Thanks,
    Mark

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    kencav is offline Banned
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    Re: P-valve Question

    actually i am going to my shop in a few hours and would be happy to share- i really just don't know how it is done!

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    musclesbmf is offline Cadillac Owners Connoisseur
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    Re: P-valve Question

    sweet... look forward to the info.

    thanks,
    Mark

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    stealthjr is offline Cadillac Owners Fanatic
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    Re: P-valve Question

    Quote Originally Posted by kencav View Post
    actually i am going to my shop in a few hours and would be happy to share- i really just don't know how it is done!

    Looking forward to pictures and a detailed write up on when and why you should do this.

    Thanks,

    Robert

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    Nutz is offline Cadillac Owners Connoisseur
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    Re: P-valve Question


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    CadV is offline Cadillac Owners Connoisseur
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    Re: P-valve Question

    I got some pictures but I need help with this as well.

    Here is a picture of the sensor (with the green x and o). x other end goes into the blower lid and would this be where the boost gauge gets its reading? o is the opposite end of the p port and I put foam on it after I capped the p port. I used foam because that's how GM had the unused port next to o.



    What about the other two ports (except x) on the sensor? Do we use foam allowing them to breathe or do we cap them?

    This is the p port with a vacuum cap (Thanks Robert for the vacuum cap) on it, is this right?



    Brent mentioned something about backing a screw out and will give ya a half pound of boost. Is the below picture the screw he is referring too?


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    Re: P-valve Question

    Maybe Jesse could tune in here and give some answers. I too would like to know what to do with the P valve to get an extra pound or so of boost. I don't want to guess which one to plug or not plug. Cecil........

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    CadV is offline Cadillac Owners Connoisseur
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    Re: P-valve Question

    Well I have some accurate information just by trial and error.

    The above pictures showing the p port capped and using foam on the opposite end is correct.

    Lastly you need to back the screw out or cut the bottom off. I cut mine because I couldn't back it out. Here is a picture...



    With the above mods my gauge hits 15 the shoots down to zero. It is crazy and I will make a video of it.

    Does anyone know what that means. I do not lose power it keeps pulling really hard. Maybe I am getting over 15

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    stealthjr is offline Cadillac Owners Fanatic
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    Re: P-valve Question

    It would be nice to hear what Jess has to say about this...

    Thanks,

    Robert

    P.S. What do you mean it shoots down to zero? With your foot at WOT it goes to zero but keeps pulling?

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    CadV is offline Cadillac Owners Connoisseur
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    Re: P-valve Question

    Quote Originally Posted by stealthjr View Post
    P.S. What do you mean it shoots down to zero? With your foot at WOT it goes to zero but keeps pulling?
    Yep at WOT gauge will hit 14.5 at the beginning and then keep climbing where it pegs 15 then it shoots down to zero without any power loss. Blower is still whistling away. Prolly maxing the gauge out.

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    stealthjr is offline Cadillac Owners Fanatic
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    Re: P-valve Question

    Quote Originally Posted by CadV View Post
    Yep at WOT gauge will hit 14.5 at the beginning and then keep climbing where it pegs 15 then it shoots down to zero without any power loss. Blower is still whistling away. Prolly maxing the gauge out.
    Better get that thing to a dyno to make sure the A/F ratio is still on the safe side. If you go...let me know!
    I wonder if the gauge is not hooked up correctly now with all of the changes you have made around the P-valve??? What does the gauge do if you just roll into the throttle and keep it around 6 PSI or so?

    Robert

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    CadV is offline Cadillac Owners Connoisseur
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    Re: P-valve Question

    The tune I am using is rich and gonna dyno it Saturday with a shop that has AC.

    Gauge will hold anything under 15. I just went out and tried to do it again but it held right under 15. It was pretty cool out the night it went to 0 something like 82 degrees.

    I am still working through some issues so I have no idea what kind of power my car is making. After I left your house I did some work on the car and figured out some stuff.

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    Re: P-valve Question

    bump

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    stealthjr is offline Cadillac Owners Fanatic
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    Re: P-valve Question

    Does nobody find it strange that Jesse has replied to many other topics and seems to be avoiding this one? Come out come out wherever you are Jesse!

    See ya!

    Robert

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    backup is offline Cadillac Owners Fanatic
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    Re: P-valve Question

    I am really curious about this mod. I smell cheap HP! Here is what I found:

    1. Disconnected O line. Found boost seemed slower to build and didn't quite reach 9psi
    2. Disconnected X line with O still disconnected. Seemed very similar to step 1 - slower to build boost and barely reached 9psi.
    3. Re-connected O, left X disconnected. Seemed to build boost VERY fast, and quickly pegged 9psi. Seat of the pants meter felt this was more responsive and more power, perhaps from faster boost build (more power sooner).

    I then reconnected all vaccuum/pressure lines and disconnected the electrical connector to the O/X valve device. Noticed it would still move the boost gauge while reving in neutral, haven't had a chance to drive it like that yet.

    I want to know what the X, O, P and V lines do, and how the valve and pressure regulator work to control boost. I don't understand how this functions. I got a hunch doing some tricks here will yield power. I want to know if the measured boost pressure as shown on the gauge is used to control the boost level, or whether it is governed by a separate mechanism such as this XOPV vaccuum/pressure valve assembly. It makes me think the 15psi shown above is real, although I don't know why the gauge would drop to zero - if the gauge information is indepependent from the boost control mechanism (the computer reading 9.0psi is not used to govern that boost).

    I do know the X/O valve is NOT the boost gauge as I was getting readings with the thing disconnected, both electrically and vaccuum lines.

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