Anyone have documentation on the Exhaust Bypass Valve operation? | FerrariChat
Buy

Anyone have documentation on the Exhaust Bypass Valve operation?

Discussion in '348/355' started by sdbmwfxr, Nov 12, 2015.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. sdbmwfxr

    sdbmwfxr Karting

    Feb 25, 2011
    238
    San Diego
    #1 sdbmwfxr, Nov 12, 2015
    Hello All,

    I'm having a custom muffler made by an outfit in Washington that has extensive experience, incredible welders and a fluid dynamics engineer, so it should be interesting to say the least.

    There's a lot of talk about the bypass valve in many threads, but I cannot find any information on when it opens and at what rate, etc. I seem to remember there being an official doc from Ferrari explaining when it opens per each gear selection and rpm, but I've had no luck finding this.

    If anyone has this information it would be greatly appreciated. I have a 95 6 speed berlinetta if that matters.

    TIA
     
  2. Dave rocks

    Dave rocks F1 World Champ
    BANNED

    Nov 23, 2012
    16,047
    Orchard Park, NY
    Full Name:
    Dave Lelonek
    #2 Dave rocks, Nov 12, 2015
    The information is in the Workshop manual
     
  3. sdbmwfxr

    sdbmwfxr Karting

    Feb 25, 2011
    238
    San Diego
    #3 sdbmwfxr, Nov 14, 2015
    . . . this begins my search for the CD I bought 5 years ago . . .
     
  4. Gialllo uno

    Gialllo uno Formula Junior

    Jul 5, 2014
    346
    Reisterstown, Maryland
    Full Name:
    Mark
    #4 Gialllo uno, Mar 8, 2016
    2800 in basically all gears except 3rd. 4000 rpm in 3rd.
     
  5. hjp

    hjp Formula Junior

    Feb 23, 2013
    591
    Kansas City, Mo.
    Full Name:
    Jerry Peterson
    #5 hjp, Mar 9, 2016
    Is it continuously variable after reaching the RPM thresholds, thereafter depending on throttle position?

    As an example, what would the valve position be at say 4200 RPM with only modest throttle, just enough to hold speed with no acceleration? Partially open? If at full throttle at 2805 RPM, would the valve be fully wide open?

    I'm guessing the RPM thresholds of 2800 and 4000 only give the valve the freedom to open if there is enough throttle demand (before the thresholds, the valve will not open at all no matter the throttle position). It would just barely open at very modest throttle positions and slowly open more and more (continuously variable) as the throttle demand becomes greater and greater.

    Is this correct?
     
  6. Rice-Racer

    Rice-Racer Formula Junior

    Jan 10, 2015
    252
    #6 Rice-Racer, Mar 9, 2016
    Pretty much as stated, first gear doesn't do much, then snaps open around 2800 rpm and so on. Not so much a progressive thing based on engine vacuum alone, the ecu's play a part in it depending on what gear and rpm.
    There's a lot of info on this, try doing a search here a bit more.
     
  7. WATSON

    WATSON Two Time F1 World Champ
    Owner Rossa Subscribed

    Sep 9, 2010
    23,689
    WI
    #7 WATSON, Mar 9, 2016
    It is not variable. It is either on or off.

    I spliced in a vacuum gauge and went for a ride. You could see when, and how, the vacuum was applied. It was really easy to do. Looked a little silly with the black hose going to the cabin...but it was temporary :)
     
  8. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,104
    Cowboy Capitol of the World
    Full Name:
    Brian Crall
    #8 Rifledriver, Mar 9, 2016
    Exactly. It is not variable due to vacuum. There is a check valve on the vacuum line and it always has sufficient vacuum to open all the way, right away. Closing happens at different RPM and throttle position than opening but that was something most even at Ferrari did not know until test drives were conducted with the computer hooked up to watch parameters.
     

Share This Page