Page 4 of 4 FirstFirst ... 234
Results 61 to 72 of 72

Thread: Which Dump Valve and where?

  1. #61
    Guest CrazySx's Avatar
    Join Date
    Jul 2005
    Location
    Isleworth/Harrow
    Posts
    5,163
    Rides
    0
    I took it apart to see what it looks like and how it works.

    Have to say it's a good design. No diaphragm to go wrong. And in my current configuration, it would have to fit upside down.








    Sent from my SM-G920F using Tapatalk

  2. #62
    Guest CrazySx's Avatar
    Join Date
    Jul 2005
    Location
    Isleworth/Harrow
    Posts
    5,163
    Rides
    0
    Also comes with 2x jubilee and vac hoses. Also a different sized vacuum nipple should you need it.



    Next I will fit it and let you know if it's any good

    Sent from my SM-G920F using Tapatalk

  3. #63
    Guest CrazySx's Avatar
    Join Date
    Jul 2005
    Location
    Isleworth/Harrow
    Posts
    5,163
    Rides
    0
    Quote Originally Posted by bevan View Post
    You say you blocked it off at the inlet? Did you show both sides of the dump valve the same pressure as this is how they seal. They actually lift on relative negative pressure from when the throttle is closed.

    Sent from my D6603 using Tapatalk
    No i didn't, but as i understand it the spring should be able to hold the pressure. This is how i understand it.

    • You are on boost (on the throttle) and running a bar of pressure
    • The intercooler cold pipe is pressurised to 1 bar before the throttle body
    • As you lift of the throttle the engine (intake Manifold) goes into vacuum
    • The DV valve is still being pressurised to release air at 1 bar.
    • The engine drops revs and produces vacuum at the intake manifold.
    • The DV valve is being sucked up by the vacuum and also blown up by 1 bar of pressure simultaneously.


    If i am right in say the above, the spring can be rated at 1 bar, as the vacuum would assist the valve to open. Whilst the throttle is open and the system is pressurised the vacuum line to the DV helps to hold it shut.

  4. #64
    Guest bevan's Avatar
    Join Date
    Nov 2013
    Location
    Gt Yarmouth
    Posts
    53
    Rides
    0
    Quote Originally Posted by CrazySx View Post
    No i didn't, but as i understand it the spring should be able to hold the pressure. This is how i understand it.

    • You are on boost (on the throttle) and running a bar of pressure
    • The intercooler cold pipe is pressurised to 1 bar before the throttle body
    • As you lift of the throttle the engine (intake Manifold) goes into vacuum
    • The DV valve is still being pressurised to release air at 1 bar.
    • The engine drops revs and produces vacuum at the intake manifold.
    • The DV valve is being sucked up by the vacuum and also blown up by 1 bar of pressure simultaneously.


    If i am right in say the above, the spring can be rated at 1 bar, as the vacuum would assist the valve to open. Whilst the throttle is open and the system is pressurised the vacuum line to the DV helps to hold it shut.
    I see your thinking. Basically the spring in a dump valve isn't like a waste gate. The spring in a dump valve is mainly there just to reset it after if dumps. It does need to be there to hold it closed but because of have a dump valve works it doesn't take much force to do this.
    A dump valve is in a closed system with the intake system, so when you have 1 Barg (gauge) in the intercooler and intake there is also 1 Barg on the top of the DV. This means across the two sides of the DV there is a 0Barg difference. Its only when you close the throttle that the engine pulls a vacuum on the top of the DV that it opens.
    It all works on differential pressure.

    When I say the two sides of the DV I mean the intercooler side and the sensing line.

    I hope that makes sense.

    Sent from my D6603 using Tapatalk

  5. #65
    Guest CrazySx's Avatar
    Join Date
    Jul 2005
    Location
    Isleworth/Harrow
    Posts
    5,163
    Rides
    0
    Quote Originally Posted by bevan View Post
    I see your thinking. Basically the spring in a dump valve isn't like a waste gate. The spring in a dump valve is mainly there just to reset it after if dumps. It does need to be there to hold it closed but because of have a dump valve works it doesn't take much force to do this.
    A dump valve is in a closed system with the intake system, so when you have 1 Barg (gauge) in the intercooler and intake there is also 1 Barg on the top of the DV. This means across the two sides of the DV there is a 0Barg difference. Its only when you close the throttle that the engine pulls a vacuum on the top of the DV that it opens.
    It all works on differential pressure.

    When I say the two sides of the DV I mean the intercooler side and the sensing line.

    I hope that makes sense.

    Sent from my D6603 using Tapatalk
    Hi Bevan, this is strictly speaking, not correct. Just imagine being in a small room with a house door and a very small window opposite that door. You are trying to hold the door closed as the wind is pushing it open. The wind is coming in from the SMALL window and behind the door. Because the wind is coming in from the small window, it gives you a little assistance to keep the door shut. Now.. instead of the wind blowing into the room through the little window, its actually sucking air out the room. Like when you open the front door and the back door of the house and wind comes in and one of them slams shut. Now the force required by you to hold the DOOR shut (while window air is being sucked out) is going to be a lot greater. so inevitably the door will open if the wind is strong enough.

    So if you are the spring, you need to be strong enough to keep the door closed and only open it a little then close it.

    LOL! not sure if that makes sense, but i hope you get my point?

  6. #66
    Guest
    Join Date
    Oct 2014
    Location
    Leicester
    Posts
    1,491
    Rides
    0
    The spring is only there to fight the vac it serves no purpose while on boost at all

    If your engine pulls -10psi max on vacuum the spring in the valve needs to be 11psi

    You could run 400psi of boost and it would still stay closed even with the 11psi spring

  7. #67
    Guest CrazySx's Avatar
    Join Date
    Jul 2005
    Location
    Isleworth/Harrow
    Posts
    5,163
    Rides
    0
    Quote Originally Posted by autosri View Post
    The spring is only there to fight the vac it serves no purpose while on boost at all

    If your engine pulls -10psi max on vacuum the spring in the valve needs to be 11psi

    You could run 400psi of boost and it would still stay closed even with the 11psi spring
    So are you saying the stock spring is too weak to hold more than 10psi vacuum and thats why the stock DV is not capable of holding anything more?

  8. #68
    Guest
    Join Date
    Oct 2014
    Location
    Leicester
    Posts
    1,491
    Rides
    0
    No the stock one has a bleed port to limit boost its built in by the factory not a fault


    Watch this
    https://youtu.be/cTMwtvZtpGA

  9. #69
    Guest
    Join Date
    Oct 2014
    Location
    Leicester
    Posts
    1,491
    Rides
    0
    This explains the blood port better than I ever could in words

    https://youtu.be/uwMlYLdw5ik

  10. #70
    Guest CrazySx's Avatar
    Join Date
    Jul 2005
    Location
    Isleworth/Harrow
    Posts
    5,163
    Rides
    0
    Ok makes sense bud. Glad we got to the bottom of it lol!

    I am looking forward to fitting the Ebay one. Looks like a good piece of kit!

    Sent from my SM-G920F using Tapatalk

  11. #71
    Guest
    Join Date
    Oct 2014
    Location
    Leicester
    Posts
    1,491
    Rides
    0
    I've got exactly the same one sat in my garage but preferred the flutter noise

  12. #72
    Guest bevan's Avatar
    Join Date
    Nov 2013
    Location
    Gt Yarmouth
    Posts
    53
    Rides
    0
    Glad you got to the bottom of it mate now don't worry about those windows and doors. What valve are you buying and where are you putting it. If you are interested ill show you how i've got mine sitting. I have only got a forge re-circ valve on there atm though. It still fits the same as my GFB one.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •