By-Pass Valve pre load adjustment ? | FerrariChat
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By-Pass Valve pre load adjustment ?

Discussion in '348/355' started by Gottaloveit, Nov 5, 2017.

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  1. Gottaloveit

    Gottaloveit Karting

    Jul 12, 2012
    52
    #1 Gottaloveit, Nov 5, 2017
    Well, in my efforts to get my 2.7 to run right and stop dropping into a rich condition periodically, I have heeded the advice of the forum and replaced the FUBAR By Pass valve that came with the car with a second hand one purchased from a fellow FChatter.

    Naturally - almost inevitably - it rattles well buzzes really. I can see why so many of you guys get so pissed with these things - man its noisy !. So I need to effect a "fix" - no matter how temporary.

    So, I want to try the preload method first and would like you comments please on the pro's and con's of lengthening ad shortening the diaphragm rod.

    Anyone got any wisdom ?

    Thanks folks
     
  2. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,727
    #2 Mitch Alsup, Nov 5, 2017
    A little mechanics wire can allow you to experiment before actually changing the bolt/nut locations.
     
  3. nathandarby67

    nathandarby67 F1 Veteran
    Owner

    Feb 1, 2005
    8,349
    Mississippi
    Full Name:
    Nathan
    #3 nathandarby67, Nov 7, 2017
    How do you know for certain the car is dropping into a rich condition? I have always been aware that can be a concern (regarding coolant temp/thermostat for instance), but never knew if there was a way to check or confirm which mode the ecu is in.

    As for the valve, mine rattles a bit too. Gets better as it heats up, but never goes completely away. I've got to do a major this winter so my plan was to fork over for the Capristo valve, as much as I don't want to.
     
  4. Drock28

    Drock28 Formula 3

    Jan 13, 2013
    1,430
    Montreal
    Full Name:
    Tony
    #4 Drock28, Nov 9, 2017
    I did the adjustment on my BPV this past spring.. its a hit or miss solution.. some say it worked others it didn't..
    for me it seemed to work for a while, but started to buzz again after a while although less.

    In my case it buzzes a bit when the car is cold.. when the car is fully warm or several heat cycles in a day.. its less and less.

    the hardest part is to break the nut at the stem.. I soaked it in lubricant first.. with a bit of pressure it freed..

    then you loosen the 3 nuts under the diaphragm.. I did two full counter clockwise turns.. if you go too much the valve can stay closed..

    when you go to screw the 3 nuts back.. you will feel the pre-load, then tighten the nut at the stem and its done..

    here is the link I referenced, when doing mine..

    https://www.ferrarichat.com/forum/threads/355-bypass-rattle-buzz-fixed.302716/#post-140024597
     
  5. Gottaloveit

    Gottaloveit Karting

    Jul 12, 2012
    52
    #5 Gottaloveit, Nov 9, 2017
    Thanks for the replies gents.

    Nathandarby67 - the rich running manifests through a couple of things. The throttle goes "lazy" and the crispness and pickup we associate with these cars just goes on a gentle throttle. At the same time you can hear what sounds like a gentle ignition miss - sounds like muted machine gun burst !. And finally - a visible sign of very black exhausts. Hit the throttle a bit harder and all is well again. Hope that helps.

    Drock28 - that's great stuff thanks very much, really helpful - just what the doctor ordered !.
     

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