Page 1 of 2 1 2 LastLast
Results 1 to 10 of 11
  1. #1

    Question BOV, surge kit why need a vacuum line

    Im trying to understand the purpose of that vacuum line affect on the BOV,

    There is negative pressure building up because off throttle, throttle valve closes ok so then the air pressure has no where to go so hence the BOV lets out the air pressure.

    So why the vacuum line below the map sensor?



  2. #2
    hitman's Avatar
    Join Date
    Aug 2006
    Location
    Ft. Lauderdale, FL
    Posts
    4,328
    +1
    12
    The vacuum is what opens the valve on the BOV.

  3. #3
    mikevv's Avatar
    Join Date
    Feb 2008
    Location
    Lake Erie
    Posts
    149

    BOV Vacuum Line

    Quote Originally Posted by hitman View Post
    The vacuum is what opens the valve on the BOV.
    When the off-throttle vacuum opens the BOV does that mply that unfiltered air is now entering the intake thru the BOV?

  4. #4
    Just relax and enjoy the ride. XLT Chad's Avatar
    Join Date
    Jan 2011
    Posts
    1,284
    +1
    116
    When the throttle is let off, the throttle body closes, but the super charger is still continuing to spin. Instead of that pressure building up as a back pressure against the supercharger, the BOV opens,releasing the excess pressure. Once the amount of pressure goes below the preset limit, the BOV closes. The vacuum line is how the valve knows the difference between boost and unwanted back pressure. If the vacuum line wasn't there, the valve would open any time boost was applied.

  5. #5
    mikevv's Avatar
    Join Date
    Feb 2008
    Location
    Lake Erie
    Posts
    149
    Quote Originally Posted by XLT Chad View Post
    When the throttle is let off, the throttle body closes, but the super charger is still continuing to spin. Instead of that pressure building up as a back pressure against the supercharger, the BOV opens,releasing the excess pressure. Once the amount of pressure goes below the preset limit, the BOV closes. The vacuum line is how the valve knows the difference between boost and unwanted back pressure. If the vacuum line wasn't there, the valve would open any time boost was applied.
    Let me ask the question this way. At idle my boost guage is at maybe minus 20psi. If that is enough vacuum to open the valve then I am sucking in unfiltered air thru the BOV.

  6. #6
    Just relax and enjoy the ride. XLT Chad's Avatar
    Join Date
    Jan 2011
    Posts
    1,284
    +1
    116
    No. the valve is spring loaded and one direction

  7. #7
    mikevv's Avatar
    Join Date
    Feb 2008
    Location
    Lake Erie
    Posts
    149
    Quote Originally Posted by XLT Chad View Post
    No. the valve is spring loaded and one direction
    So air can only go out and not in? That would explain it but my Greddy BOV doesn't look like it has a 1 way valve. Am I wrong?

  8. #8
    i will get all the rest i need when im dead corkycat's Avatar
    Join Date
    Jan 2009
    Location
    uk
    Posts
    840
    +1
    1
    The dump valve has basically two operating conditions; throttle open, and throttle closed. When the throttle is open, the boost pressure coming into the valve from below the diaphragm is equalled by the pressure onto the top of the diaphragm that comes via the small hose from the engine plenim chamber. As the pressures are equal, the spring holds the diaphragm onto its seat, and prevents the pressure venting away. When the throttle is closed, the pressure coming into the top of the valve is significantly reduced, (often to a vacuum), and the pressure below the diaphram lifts it away from its seat, allowing the excess pressure to vent away. As the throttle is reopened, the pressures again equalise, the spring pushes the diaphragm onto its seat, and the boost pressure cannot vent away.

  9. #9
    mikevv's Avatar
    Join Date
    Feb 2008
    Location
    Lake Erie
    Posts
    149
    Corky, Chad
    Thanks for the help. I think I have it now.

  10. #10
    mikevv's Avatar
    Join Date
    Feb 2008
    Location
    Lake Erie
    Posts
    149

    Greddy BOV adjustment

    Quote Originally Posted by corkycat View Post
    The dump valve has basically two operating conditions; throttle open, and throttle closed. When the throttle is open, the boost pressure coming into the valve from below the diaphragm is equalled by the pressure onto the top of the diaphragm that comes via the small hose from the engine plenim chamber. As the pressures are equal, the spring holds the diaphragm onto its seat, and prevents the pressure venting away. When the throttle is closed, the pressure coming into the top of the valve is significantly reduced, (often to a vacuum), and the pressure below the diaphram lifts it away from its seat, allowing the excess pressure to vent away. As the throttle is reopened, the pressures again equalise, the spring pushes the diaphragm onto its seat, and the boost pressure cannot vent away.
    Corky
    With open throttle if the pressure on the "small hose" "equalizes" with the SC pressure to keep the valve closed then how does the adjusting screw on the Greddy bov limit the boost? As long as the pressure is equal on both sides the valve should stay shut.

Page 1 of 2 1 2 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Replies: 2
    Last Post: 03-07-2016, 08:13 PM
  2. Vacuum line off BOV keeps ripping off
    By Corey R. in forum Yamaha PWC Performance (4-stroke)
    Replies: 5
    Last Post: 04-09-2012, 12:42 PM
  3. Vacuume Line install for blowoff valve
    By Fatty in forum 4-Tec Performance
    Replies: 9
    Last Post: 10-12-2007, 09:13 PM
  4. Riva Power Filter Kit.......why do I feel scammed?
    By Fatty in forum 4-Tec Performance
    Replies: 42
    Last Post: 07-04-2007, 05:57 PM
  5. plugging vacuum line for bov
    By excess in forum 4-Tec Performance
    Replies: 4
    Last Post: 08-16-2006, 07:03 PM

Posting Permissions

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