Page 7 of 9 FirstFirst ... 56789 LastLast
Results 61 to 70 of 86
  1. #61
    butterbean_29512's Avatar
    Join Date
    Sep 2013
    Location
    Bennettsville, SC
    Posts
    1,469
    +1
    147
    Quote Originally Posted by mittens View Post
    Yes the air can stop. Don't dissagree my blown 427 has a blow off/bypass valve as well. But this threat was if one was needed for the clutch so saying the blow back will spin it backwards is what I was arguing.

    the air can't go forward and the valve helps Bleed it off.
    The BOV keeps the compressor from operating in the surge index. Each centrifugal compressor...no matter it's intended use can aerodynamically compress only so much air. Once the compressor reaches the surge index it has compressed all the air it mechanically can, and airflow into the inlet stops. The compressed air on the outlet side of the compressor suddenly has somewhere to release all its pressure to...the inlet of the compressor. Surge is a violent phenomenon, and can severely damage a compressor. Each surge occurrence reduces the capacity of the compressor a tiny bit. Wondering why your SC suddenly won't make as much boost anymore??? Surge could be the reason! Also...the surge index comes down as inlet temps go up. Therefore your SC is more susceptible to surge in the summer. So...protect those dang superchargers, don't cheap out!! Get a BOV for them!! Its essential!

  2. #62
    Quote Originally Posted by butterbean_29512 View Post
    The BOV keeps the compressor from operating in the surge index. Each centrifugal compressor...no matter it's intended use can aerodynamically compress only so much air. Once the compressor reaches the surge index it has compressed all the air it mechanically can, and airflow into the inlet stops. The compressed air on the outlet side of the compressor suddenly has somewhere to release all its pressure to...the inlet of the compressor. Surge is a violent phenomenon, and can severely damage a compressor. Each surge occurrence reduces the capacity of the compressor a tiny bit. Wondering why your SC suddenly won't make as much boost anymore??? Surge could be the reason! Also...the surge index comes down as inlet temps go up. Therefore your SC is more susceptible to surge in the summer. So...protect those dang superchargers, don't cheap out!! Get a BOV for them!! Its essential!

    Do you recommend a BOV for a stock yamaha?

  3. #63

    Join Date
    Jul 2014
    Location
    Canyon Lake, TX
    Posts
    596
    +1
    76
    So no one has proof that the throttle plate closes during rev limit.
    Why does the BOV actuate then? Im stumped here. im thinking people are not hearing the BOV but they are hearing the SC clutch, which sounds a lot like a bov when you hit rev limit.
    max speed of the throttle flap is slow as shit compared to what is needed to limit over revving. can a tuner please chime in?

    It sounds a ton like a BOV when i chop throttle. and I dont have one.


  4. #64
    Saum700p's Avatar
    Join Date
    Sep 2017
    Location
    New Orleans
    Posts
    470
    +1
    79
    Quote Originally Posted by Reaper9789 View Post

    It sounds a ton like a BOV when i chop throttle. and I dont have one.
    That's just the sound you destroying your clutch...

  5. #65
    mittens's Avatar
    Join Date
    Mar 2018
    Location
    Huntsville, AL
    Posts
    636
    +1
    60
    A rev limit I snot throttle actuated it never is, Normally fuel or ignition. and with this being a factor boosted motor I would hope and assume its ignition, leaning it out by injectors to limit is dumb.

    the limiter hitting the motor un revs its un reving from the lack of spark...

  6. #66
    butterbean_29512's Avatar
    Join Date
    Sep 2013
    Location
    Bennettsville, SC
    Posts
    1,469
    +1
    147
    Quote Originally Posted by Dreadknotz View Post
    Do you recommend a BOV for a stock yamaha?
    Every centrifugal compressor/supercharger needs one. It will save your clutch, or extend its life.

  7. #67
    butterbean_29512's Avatar
    Join Date
    Sep 2013
    Location
    Bennettsville, SC
    Posts
    1,469
    +1
    147
    Quote Originally Posted by Reaper9789 View Post
    So no one has proof that the throttle plate closes during rev limit.
    Why does the BOV actuate then? Im stumped here. im thinking people are not hearing the BOV but they are hearing the SC clutch, which sounds a lot like a bov when you hit rev limit.
    max speed of the throttle flap is slow as shit compared to what is needed to limit over revving. can a tuner please chime in?

    It sounds a ton like a BOV when i chop throttle. and I dont have one.
    The intake vacuum actuates the BOV. Vacuum changes with load and throttle position.

  8. #68
    JESUS G's Avatar
    Join Date
    Jun 2007
    Location
    South Florida
    Posts
    603
    +1
    199
    Hi guys...

    I talked to Jerry about some other stuff, but he asked me If i could trough some info here regarding how the limits works on Yamaha ECU... So here is the info ( I hope it helps):

    There is 4 basics limits for Yamaha ECUs

    Boost Limit which is about 11psi... once you reach or get over 11 Psi ECu close throttle body to keep the RPM where you dont reach more than 11Psi.

    Speed Limit , which really is sort of RPM limit. In a FX model ( for example ) it's set at 7700 RPM... so once ECU reads over those RPM, close the Throttle body to keep the rpm not going over 7700rpm.... there is also different delays depend on which models.

    Rev limits :

    Ignition : cyl 1 7800- cyl 2 7851 - cyl 3 7999 - cyl 4 8148

    Fuel cut : 9500


  9. #69
    Quote Originally Posted by butterbean_29512 View Post
    Every centrifugal compressor/supercharger needs one. It will save your clutch, or extend its life.
    Show me evidence! This is the third time I have said this, there are no studies that prove what you are saying.

  10. #70

    Join Date
    Nov 2018
    Location
    North Carolina on Jordan Lake
    Posts
    514
    +1
    66
    Has anyone noticed that these engines have no flywheel. A flywheel slows down an engine`s rpm acceleration, because these engines do not have a flywheel on their cranks, the compressor could suffer from too great of acceleration from the engine`s rpm`s. The sprag clutch gives the engine a degree of slippage and the BOV alleviates some load too and avoids stripping of the gears on the compressor and breaking compressor shafts. Another thing is the direct engaged impellers give these engines a constant load, used in place of flywheel load. I think when the load is lost on the impellers by coming out of the water( and the smaller impellers we put on them, like a stall speed converter), allows the engine to accelerate very fast in RPM`s is causing the clutches to fail early they are engaging with so much torque.

    Take Care
    C J
    Last edited by cjk6119; 03-25-2020 at 11:15 PM. Reason: sp

Page 7 of 9 FirstFirst ... 56789 LastLast

Thread Information

Users Browsing this Thread

There are currently 2 users browsing this thread. (0 members and 2 guests)

Similar Threads

  1. RIVA Yamaha SVHO Power Cooler with Free BOV Includes FREE HKS BOV - Special Sale
    By Green Hulk in forum Yamaha PWC Performance (4-stroke)
    Replies: 0
    Last Post: 11-09-2018, 12:21 PM
  2. RIVA Yamaha SHO GEN-2 Power Cooler with Free BOV Includes FREE HKS BOV - Special Sale
    By Green Hulk in forum Yamaha PWC Performance (4-stroke)
    Replies: 0
    Last Post: 11-09-2018, 12:18 PM
  3. Are there California restrictions put on the new Yamaha's?
    By Kirk1964 in forum Yamaha PWC Performance (4-stroke)
    Replies: 4
    Last Post: 08-21-2015, 02:33 PM
  4. just put in bov check it
    By stevorxp007 in forum 4-Tec Performance
    Replies: 32
    Last Post: 08-05-2010, 09:27 PM
  5. Yamaha Fx High Out Put<------
    By Gj#6 in forum Yamaha PWC Performance (2-stroke)
    Replies: 13
    Last Post: 02-18-2007, 04:48 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
  •