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  1. #1

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    New Riva Blow off in stage III

    Question,
    Why Riva keeps putting BOV and upgrading it now to the aluminum one when it is actually bad for the supercharger.
    just curious
    thanks


  2. #2
    EZ Dock of Long Island Shibby1485's Avatar
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    i'm guessing because the new SC flows so much air and boost that if the TB shuts very quickly the SC could experience compressor surge with the backwards flow of air

  3. #3
    ut oh back to the BOV.
    So does it mean that with all the extra air and boost be it a new RR SC, les kit or Riva super SC , you would now need a billet BOV ?

  4. #4
    Les says not to use the BOV becuase it does not allow for spin down

  5. #5
    Site Admin Green Hulk's Avatar
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    The new Riva supercharger delivers a very large volume of air that you must use a BOV.... a BIG one to release un needed air when part throttle. If not you will experience horrible compressor surge. It may not be good for the clutch, but its a necessity with this supercharger.

  6. #6
    Riva said there SC produces 10.5 boost. The new RR is like 9 isn't it or was it 10 ?

    So the new RR doesn't need a BOV, wouldn't it be moving as much air as the RR ?

  7. #7

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    well i am going to be using a greddy type s BOV which i used in my car. It will work fine at that boost.

    Can't wait to get my stage III parts.(july???)

  8. #8
    EZ Dock of Long Island Shibby1485's Avatar
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    Quote Originally Posted by Kinchyle
    Riva said there SC produces 10.5 boost. The new RR is like 9 isn't it or was it 10 ?

    So the new RR doesn't need a BOV, wouldn't it be moving as much air as the RR ?
    air flow vs boost pressure.... Rotax racaing is less boost AND less air flow. Riva is more boost AND more air flow..... more CFMs at more boost is alot of air!

    think about the air the B and C kits are pushing... machined housings, more flow and alot more boost...

    regardless, i'm sure we'll never reach a conclusion on BOVs. If the Riva kit is prone to compressor surge, then the B kit has to be, at least it would only be logical that was the case. if you can run a B kit which is machined housing and 13psi with no BOV with no problems, than i would THINK you can safely do so with a slightly more mild SC like Riva's which is machined housings with a little less boost.

  9. #9
    Legend in my own mind Sirhc7897's Avatar
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    Man you guys are hung up on this whole "boost" thing...

    You've got to realize "boost" doesn't matter. It's nothing more than a measure of backpressure...

    If this thing is moving more cfm's with less resistance and turbulence than it's going to be an issue.

    From what I understand this thing actually moves more air than the motor can process at less than WOT and therefore this unprocessed air is going to back up in the area between the supercharger and the throttle body. It's going to have to go somewhere and since it can't go through the motor it's going to go back through the supercharger which WILL wear it all out prematurely because:

    -the supercharger bearings are going to heat way up from all the added resistance
    -the clutch is going to be in a perpetual state of slip as well

    At WOT the supercharger can process it all so it won't be a issue but at lower rpms it's going to have to have somewhere to go...Better out through a BOV (or actually in this scenario think of it more as a pressure activated boost bypass) than back through the supercharger or out a whole somewhere that all that extra pressure is going to punch out...

    That's how they're going to greatly improve the bottom end of the ski...by essentially pre-loading the intake tract with a surplus of air...That way there will "instant" power (it's a way to cheat the mechanical driven centifugal supercharger setup to avoid the soft spot down low before you get into enough rpms to make "boost" vs vacuum. They're just moving that swing point much lower in the rpm scale - which is going to require a bleed off of pressure below WOT)

    i notice on my ski the 0psi point is somewhere around 5k rpms (or maybe 6k?)...after that you start building "boost"...I bet this supercharger setup (while not only making even more "boost") will hit that "0psi" point lower in the rpm band...IMO

  10. #10
    All I can say is the BOV on a stage 2 does absolutley nothing to extend clutch life. That was the reason they put it on. The sea doo racers that say that it is not necessary to have them on, I would have to agree with them. But if you get the intercooler and it comes with it, why not have it I guess. Definitely not worth a seperate purchase.

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