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  1. #1
    JPR's Avatar
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    Pump tunnel relief valve

    Does anyone have a breakdown on how the valves used for pressure relief function and internal components, is it spring or cylinder etc. what KPA are they rated for LB motorsports kit as I canít get hold of them.
    Mine are stuck wide open and this idiot glued them in so they were water tight and a mission to remove to look into them from intake end
    Last edited by JPR; 01-06-2019 at 03:44 PM.


  2. #2
    Bob 1tommygunner1927's Avatar
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    PRVs consist of a check valve, ball valve, hose, inlet/outlet. The check valve opens with little pressure. The ball valve can be moved to the closed position if the check valve becomes stuck open.
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  3. #3
    JPR's Avatar
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    Quote Originally Posted by 1tommygunner1927 View Post
    PRVs consist of a check valve, ball valve, hose, inlet/outlet. The check valve opens with little pressure. The ball valve can be moved to the closed position if the check valve becomes stuck open.
    so shut it off and forget about it . I didnít install a ball valve just what came with the kit. Can I assume that they are spring and disc type? What fixed pressure would they be u think 350 or 500 kpa? Appreciate any help.

  4. #4
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by JPR View Post
    so shut it off and forget about it . I didn’t install a ball valve just what came with the kit. Can I assume that they are spring and disc type? What fixed pressure would they be u think 350 or 500 kpa? Appreciate any help.
    That's what I plan to do, just shut it off. In the pic, the ball valve is open. When its open, so are the PRVs, even at idle! Supposedly, it can affect acceleration and top speed. But the purpose of the PRVs is to help avoid pump stuffing. That it does! Yes, spring loaded disc, like a sink stopper! The spring is weak, opens at about 1 or 2 pounds.

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    JPR's Avatar
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    Quote Originally Posted by 1tommygunner1927 View Post
    That's what I plan to do, just shut it off. In the pic, the ball valve is open. When its open, so are the PRVs, even at idle! Supposedly, it can affect acceleration and top speed. But the purpose of the PRVs is to help avoid pump stuffing. That it does! Yes, spring loaded disc, like a sink stopper! The spring is weak, opens at about 1 or 2 pounds.
    Don’t suppose you would know what KPA they are ?

  6. #6
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by JPR View Post
    Don’t suppose you would know what KPA they are ?
    200 psi! 1,378 kPa.

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    JPR's Avatar
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    So I pulled it out. The spring is so light on this valve I can see y it stays open. I thought the whole idea of a PRV would be to stay shut until it gets closer to a unsafe psi level in the tunnel then open. Itís just like running a straight through 19mm outlet from the tunnel with this set up on a light spring. Am I missing something here? Stupid question but Disc opens outward so nut to intake hose?
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  8. #8
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by JPR View Post
    So I pulled it out. The spring is so light on this valve I can see y it stays open. I thought the whole idea of a PRV would be to stay shut until it gets closer to a unsafe psi level in the tunnel then open. It’s just like running a straight through 19mm outlet from the tunnel with this set up on a light spring. Am I missing something here? Stupid question but Disc opens outward so nut to intake very lighthose?
    There should be an arrow on the body of the valve showing direction of flow. Yes, the spring is light, its why the valve is always open, and why it affects acceleration/top speed. But again, the propose of the valve is to raise the point of pump stuffing; it bleeds off pressure. These valve are inexpensive but heavy. Summit Racing has one way checks valves. They are light weight aluminum but cost $50+.

    Summit Racingģ One-Way Check Valves SUM-220195B


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    DR2006RXP's Avatar
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    Quote Originally Posted by 1tommygunner1927 View Post
    There should be an arrow on the body of the valve showing direction of flow. Yes, the spring is light, its why the valve is always open, and why it affects acceleration/top speed. But again, the propose of the valve is to raise the point of pump stuffing; it bleeds off pressure. These valve are inexpensive but heavy. Summit Racing has one way checks valves. They are light weight aluminum but cost $50+.

    Summit Racing One-Way Check Valves SUM-220195B

    I wonder how the (3) 7mm cooling ports on the 2018 rxpx-300 affect pump tunnel pressure ???

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    Cosmicbrut's Avatar
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    Quote Originally Posted by JPR View Post
    So I pulled it out. The spring is so light on this valve I can see y it stays open. I thought the whole idea of a PRV would be to stay shut until it gets closer to a unsafe psi level in the tunnel then open. It’s just like running a straight through 19mm outlet from the tunnel with this set up on a light spring. Am I missing something here? Stupid question but Disc opens outward so nut to intake hose?
    Thats the impression I had too until I installed them on my ski with a pressure sensor. Basically the check valve is there to prevent air being sucked in at take off because there is actually vacuum in the tunnel until you get on plane. The air being sucked in causes terrible cavitation. I ride in a river so every now and then a small piece of debris gets stuck in the check valve causing it to stick open and cavitate on take off. The check valve in my setup only has a 5 lb spring in it.

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