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  1. #1

    air bypass system

    I got my manual today and I may have good news:

    As many are aware, importracer got more boost with the block off of the blow off valve from 10 psi to 11.x psi. Here is fact based on the manual:

    1. The relief valve is used to blow off pressurized air when the throttle is released (auto world, I always refer to it as blow off valve). It is activated when vaccum is around -400 mmHg)
    2. The blow off valve (Ultra 250X manual's reference) is there to bleed off pressurized air over 1390 mmHg. I believe this is a safety feature to prevent overboosting. 1390 mmHg is 26.878 psi or 12.182 psi over atmosphere. So the blow off valve will start to open at 12.182 psi to bleed off pressurized air. This should also mean the ski's fuel map is good up to 12.182 psi.

    So it seems like some of the Ultra has a soft spring on the blow off valve. It should never be operational according to the manual. In idea world, the ski should boost 11.4 psi and blow off valve open at 12.182 psi, thus blow off valve never should open.

  2. #2

  3. #3

    Join Date
    Feb 2007
    Bowie, MD
    Will any of these mods give me a higher top speed or improve acceleration. I'd like to see some real world testing and what each of these individual products do for the Ultra 250.


  4. #4

    Join Date
    Jun 2005
    rome ga
    The blow off valve is leaking @ full throttle.

  5. #5

    Join Date
    Sep 2006
    S. Florida
    RXPSTAN, didn't you try to block it off?

    Quote Originally Posted by rxpstan View Post
    IF YOU BLOCK IT OFF IT GETS HOT. Ran it hard for 5 minutes it started loosing RPMs.

  6. #6
    Im no expert on this but if there was an adjustable one to replace this that would only open at 12psi then it would hold and not start leaking at 5 psi on up. Description of operation is on page 9-13

    Any one with a Service Manual can look on Page 9-10 and see that Kawi was using an adjustable unit during testing. This was the setup on the PreProduction units. Now the production line has a plastic one.

    So someone should offer an adjustable unit, set it to 12psi for us to replace the stock unit.

  7. #7
    Leak at 5 psi? I am at work now, but I thought the manual says test the valve for opening at 12.182 psi, if not replace it. So there should be no bleeding up to 12.182 psi, otherwise it is a malfunction valve!!!

    Maybe the factory screwed up and install the vacuum opening valve on the positive pressure opening valve?

  8. #8
    I must have said that wrong. Im saying that some are bleeding air as low as 5psi. They should not be doing that at all untill 12.x psi.

  9. #9
    Importracer's Avatar
    Join Date
    Feb 2007
    San Antonio, Tx
    I am still wondering why its installed on a supercharged engine anyway??? If it was a turbo I could see the possibility of it overboosting if the wastegate failed but with a belt drive blower there really is not a condition for it to overboost unless its was over revved. If you ever want to raise the boost your gonna have to block it off anyway.

  10. #10
    Water Bum Rodneyae's Avatar
    Join Date
    Dec 2006
    Roanoke, Va
    And one have a pic of one? I have in the auto world crushed them to make the spring have more tention and hold it closed. I am running 30 Psi of boost and using one from a mitsu. eclipse that has been crushed with no leaking. Stock psi where these start leaking is around 17 psi. So if someone has a pic There might be away to crush it. Wait it is probley plastic, if so this will not be an option.

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