Materials to Maintain Your ZHP IIIII Hand Protection IIIII Tools to Maintain Your ZHP
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  1. #21
    Join Date
    Mar 2011
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    Philadelphia
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    For anyone who has doubts about the CDV, try this:

    Remove your CDV and clean it really well
    Blow into both sides

    You'll notice that the return direction has a ton more resistance than the release direction. If you can feel that much resistance with your breath, there will definitely be a very large pressure drop in the actual system too. The reason the pressure drop is only in one direction is because the CDV has a mechanism that allows fluid to go around the restriction in that one direction.

  2. #22
    Join Date
    Nov 2012
    Location
    Seattle, WA
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    1,212
    Man, I REALLY need to get rid of mine. Every time I have a bad shift I blame the CDV. LOL
    Fuelly

  3. #23
    Haha, nothing better than having nothing but yourself to blame

    Zebra Horse Power - PSA: The Hypermiling Thread
    Kevin Savino-Riker
    Cogito Automation, LLC.
    I'm new at BMWs.

  4. #24
    Join Date
    Jun 2011
    Location
    Redondo Beach, CA
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    Quote Originally Posted by terraphantm View Post
    For anyone who has doubts about the CDV, try this:

    Remove your CDV and clean it really well
    Blow into both sides

    You'll notice that the return direction has a ton more resistance than the release direction. If you can feel that much resistance with your breath, there will definitely be a very large pressure drop in the actual system too. The reason the pressure drop is only in one direction is because the CDV has a mechanism that allows fluid to go around the restriction in that one direction.

    Not exactly, there is no cut off mechanism in the CDV therefore it cannot limit pressure. It simply restricts the flow of the fluid to reduce the power of the return stroke.
    2006 CiC 6MT
    ZHP, Cold Weather, Xenon
    Sapphire Black / Black Leather / Black Cube

  5. #25
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    Mar 2011
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    Philadelphia
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    Quote Originally Posted by wsmeyer View Post
    Not exactly, there is no cut off mechanism in the CDV therefore it cannot limit pressure. It simply restricts the flow of the fluid to reduce the power of the return stroke.
    http://en.m.wikipedia.org/wiki/Orifice_plate

    Pressure (and velocity) will be greater before the restriction than after. It doesn't limit pressure in the sense that the pressure cannot exceed X psi. But there is certainly a pressure drop across such a restriction.

  6. #26
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    Jun 2011
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    Quote Originally Posted by terraphantm View Post
    Pressure (and velocity) will be greater before the restriction than after. It doesn't limit pressure in the sense that the pressure cannot exceed X psi. But there is certainly a pressure drop across such a restriction.
    Nope.

    See the section titled "Incompressible flow through an orifice" in the link you gave.
    2006 CiC 6MT
    ZHP, Cold Weather, Xenon
    Sapphire Black / Black Leather / Black Cube

  7. #27
    Join Date
    Jan 1970
    Location
    Liberty Township, OH
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    37,935
    Does there not have to be a pressure drop for the equation to hold true?

    Call Me Dane l 2/2004 330i ZHP l 18x8 ET45 BBS CK's wrapped with Michelin Pilot Sport AS3+ @ 245-40-18 l KW V1 Coilovers in front l KW V1 springs w/ Bilstein B8 dampeners in rear l BMW Performance Rotors l UUC StrutBarbarian l Racing Dynamics Rear Strut Bar l Jim Conforti Shark Injector l Light Birch Interior Trim l Bimmian Celly Mount l M3 Trunk Mat l l e90 Performance E-Brake & Shift Knob l M3 Tri-Stitched Boots l AL Headlight Retrofit with ZKW Lenses l CobyWheel Wrap w/M3 Stitching l LCM sw 4.5 triple blink and rear fogs l Maple Interior Trim

  8. #28
    Join Date
    Jan 1970
    Location
    Asheville, NC
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    2,591
    So carry the one, then divide by......oh hell. gonna have to wait till little man goes to bed to digest that equation.
    "No, Donny, these men are nihilists, there's nothing to be afraid of"

    09 135i Msport 6mt
    04 330i ZHP (sold)
    David

  9. #29
    Join Date
    Jan 1970
    Location
    Liberty Township, OH
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    Additionally, this chart shows expected pressure drop through a cylindrical sharp edged orifice, which I think the CDV essentially is.



    http://www.womackmachine.com/enginee...-orifices.aspx

    The only place I can think of where an "orifice" is encountered with no corresponding pressure drop is in a stage (Moving blade-fixed blade-moving blade) through a reaction turbine.....but then again....steam isn't an incompressible fluid either.

    Call Me Dane l 2/2004 330i ZHP l 18x8 ET45 BBS CK's wrapped with Michelin Pilot Sport AS3+ @ 245-40-18 l KW V1 Coilovers in front l KW V1 springs w/ Bilstein B8 dampeners in rear l BMW Performance Rotors l UUC StrutBarbarian l Racing Dynamics Rear Strut Bar l Jim Conforti Shark Injector l Light Birch Interior Trim l Bimmian Celly Mount l M3 Trunk Mat l l e90 Performance E-Brake & Shift Knob l M3 Tri-Stitched Boots l AL Headlight Retrofit with ZKW Lenses l CobyWheel Wrap w/M3 Stitching l LCM sw 4.5 triple blink and rear fogs l Maple Interior Trim

  10. #30
    Join Date
    Dec 2012
    Location
    Salt Lake City, UT
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    6,871
    After going over hydraulics in my physics class just last week, this all makes sense.

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