Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 23
  1. #1

    Smile Do away with SC slip by building waste gate

    wouldnt it be much easier to build a type of waste gate on intake between SC and IC or TB and have it set to release pressure at 15psi or wherever you want it.Much like the wastegates on turbos that limit exhaust pressure.Or would it totally mess up the fuel system.It just seems that this would be much better than the type of slip set up in todays SC.I mean then on race boats you could be positive about your intake pressures at rpm instead of adjusting slip which can change after installation,with different oils,etc.Plus then full sythetic slippery oils could be used not the current seadoo or jaso cert.oils?Just a thought after rebuild 5 or 6 SC this year any thoughts on this>Marvin


  2. #2
    speedskixp's Avatar
    Join Date
    Feb 2008
    Location
    venice fl.
    Posts
    8,117
    +1
    120
    The clutch is there to keep the shaft from snapping or whelel from blowing apart on sudden decel when the momentum of the wheel want's to keep it spinning. The wheel is spinning @ 40000+ rpm's or 5.2:1 over the engine rpms. If you decel and the engine drops from 8000 to 3000 the wheel cant drop 26000 rpm's in a split second without something breaking so the clutch is there to cushion this. Has nothing to do with the boost really.

  3. #3
    Eric Ocman's Avatar
    Join Date
    Aug 2008
    Location
    Cataula, Georgia, United States
    Posts
    4,700
    +1
    77
    The SC is gear driven the turbo is gas/air driven. You cannot equate/think about them the same way. What u refer to is basically a BOV which some members have proven actually hurt our scs. The only better approach seems to be the rotax hydraulic setup which is expensive and requires machining.

  4. #4
    mongo's Avatar
    Join Date
    Jul 2007
    Location
    Stephensville, La
    Posts
    154
    I would think with all the machinists and knowledgable people on this forum, that someone could come up with a clicker type one way lockup clutch.

  5. #5
    speedskixp's Avatar
    Join Date
    Feb 2008
    Location
    venice fl.
    Posts
    8,117
    +1
    120
    Quote Originally Posted by mongo View Post
    I would think with all the machinists and knowledgable people on this forum, that someone could come up with a clicker type one way lockup clutch.
    Sprag clutch is what the yammi's are using but they fail quite often also because of the pounding they take engaging when on and off the throttle. Put the sea doo clutch together with the yammi sprag and now you have something.

  6. #6
    mongo's Avatar
    Join Date
    Jul 2007
    Location
    Stephensville, La
    Posts
    154
    Now your talking. I was thinking even something as simple as ramp notches in the gear and matching ramps on the washers.

  7. #7
    "Hustler" Inkaddict's Avatar
    Join Date
    Aug 2007
    Location
    NJ
    Posts
    4,712
    +1
    26
    Quote Originally Posted by Ocman View Post
    The SC is gear driven the turbo is gas/air driven. You cannot equate/think about them the same way. What u refer to is basically a BOV which some members have proven actually hurt our scs. The only better approach seems to be the rotax hydraulic setup which is expensive and requires machining.
    Im somewhat new to the 4tech motor and sc so pardon my ignorance but how does a BOV hurt an SC?

  8. #8
    Eric Ocman's Avatar
    Join Date
    Aug 2008
    Location
    Cataula, Georgia, United States
    Posts
    4,700
    +1
    77
    Quote Originally Posted by Inkaddict View Post
    Im somewhat new to the 4tech motor and sc so pardon my ignorance but how does a BOV hurt an SC?
    The BOV will try to slow the impeller down to fast which results in more stress/pressure on the clutches than the normal deceleration process. Ideally the engine would never have an abrupt rpm fluctuation. The pressure built inside the boost tract actually protects you a bit. The rapid pressure loss is immediately transferred to the clutches.

  9. #9
    Site Admin Green Hulk's Avatar
    Join Date
    Apr 2005
    Location
    Morgan City, LA
    Posts
    36,398
    +1
    2,524
    Quote Originally Posted by Inkaddict View Post
    Im somewhat new to the 4tech motor and sc so pardon my ignorance but how does a BOV hurt an SC?

    Here's a good post by Rory which explains it perfectly

    Quote Originally Posted by R88ory RXP View Post
    Basicly if you were pulling say 8100 and chop the throttle the engine RPM drops real fast and the SC dont want to slow down so fast so the clutch has to slip. By not running the BOV the wheel come up against the air and it slows it down faster then if you have a BOV relesing the boost which results in less slip, the backed up pressure acts as a brake on the wheel to bring it down to the engine speed faster. If you let that pressure out (BOV) then the wheel comes up against no pressure and relys completly on the clutch to slow the wheel back down which means its slipping for longer causing more wear.

    There are issues with not having a BOV tho as you have more chance of blowing a boost pipe off, although this is very rare.

    Hope that is understandable and answers your question.

    R88

  10. #10
    R88ory RXP's Avatar
    Join Date
    Feb 2008
    Location
    Kent, England
    Posts
    2,737
    +1
    46
    Quote Originally Posted by Inkaddict View Post
    Im somewhat new to the 4tech motor and sc so pardon my ignorance but how does a BOV hurt an SC?
    Because by running a BOV it makes the clutch slip for longer when chopping the throttle, If you dont have a BOV the boost backs up and acts as a brake on the wheel to slow the SC back down the match the engine again.

    Say at 8000 engine RPM the SCer is doing 40,000+ rpm so when you drop the throttle and the engine come back to idle in less then a second the SC has to slow down by 30,000+ rpm in the same time that is alot of turning energy that needs to slow down, so at this point the clutch starts to slip bringing the wheel down gradually to match the engine again, If you had a BOV fitted the boost from the SC gets blown out into the hull, if you dont have a BOV it backs up against the throttle plate and trys to go backwards through the SCer, this inturn slows the wheel down faster then the clutch could on its own, this means the clutch has to do less work and therefore has less heat put into it and less wear.

    R88

Page 1 of 3 1 2 3 LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Replies: 4
    Last Post: 08-30-2017, 12:16 PM
  2. Replies: 53
    Last Post: 03-01-2017, 05:59 PM
  3. Pro's and Con's of doing away with a waterbox
    By andreasenracing in forum 4-Tec Performance
    Replies: 24
    Last Post: 12-09-2010, 09:48 AM
  4. Help With sc Clutch
    By bayline03 in forum 4-Tec Performance
    Replies: 13
    Last Post: 09-17-2006, 02:39 PM
  5. Do you need sc clutch if you have a BOV
    By tchies in forum 4-Tec Performance
    Replies: 1
    Last Post: 08-09-2005, 01:31 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
  •