Exhaust Bypass Valve Default Position (Engine not running) | FerrariChat
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Exhaust Bypass Valve Default Position (Engine not running)

Discussion in '348/355' started by Qavion, Aug 17, 2016.

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  1. Qavion

    Qavion F1 World Champ
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    Ian Riddell
    #1 Qavion, Aug 17, 2016
    Hi folks,
    Just wondering what position the bypass valve should be in with the engine not running.

    I'm getting a weird graunching/rattling sound from the rear of the car a few minutes after engine startup at low rpms which lasts maybe 10 seconds . It sounds like something opening (like a squeaky gate). According to the previous history of my car, the bypass valve was "rebuilt" about 4 years ago (probably no more than a couple of thousand km's ago).

    I was thinking that if the default position is open (engine not running) and on start-up, the valve closes (and open opens when engine warm/high rpm), that the valve may be jamming and only closes after a few minutes of engine vibration. I have a Mille Miglia exhaust, but I still see a bypass valve/actuator setup.

    If the default position is closed with engine off, then I can probably go looking elsewhere for the sound.

    Thanks.
    Cheers
    Ian.
     
  2. MAD828

    MAD828 F1 Rookie

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    Elliott Caras
    #2 MAD828, Aug 17, 2016
    Default is closed position. Unless you have a capristo bypass and modified solenoid that defaults to open. On start up with a stock setup the bypass is closed.
     
  3. Qavion

    Qavion F1 World Champ
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    #3 Qavion, Aug 17, 2016
    Thanks, Elliot.

    I probably used the wrong definition of "default". So, just to clarify, with engine off, the valve is open. When the engine is started, vacuum closes the valve, and it only reopens with my right foot on the floor :)

    So the bypass valve could still be the source of this sound (maybe). I'll try and get a recording of it.

    Cheers
    Ian.
     
  4. MAD828

    MAD828 F1 Rookie

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    #4 MAD828, Aug 18, 2016
    It's closed all the time. Vacuum opens it on signal from the ecu. The source of the sound is most likely the bypass anyway. I have seen brand new (I fitted it) OEM bypass rattle from new! Rebuilt I haven't seen any that last at keeping the rattle at bay. I opted for the capristo valve and now I think the best option is Gothspeeds version.
     
  5. Qavion

    Qavion F1 World Champ
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    #5 Qavion, Aug 18, 2016
    I was looking for an excuse to buy the Gothspeed version, but I think I'll wait until I can confirm the fault. It's more than just a rattle, it's a loud groan which disappears (with no change in revs). Sounds like something in transit to me.

    Thanks again.
    Cheers
     
  6. gothspeed

    gothspeed F1 World Champ

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    #6 gothspeed, Aug 22, 2016
    The OE bypass is 'normally closed' until the ecu powers the bypass solenoid and allows vacuum to the actuator. The cappy bypass is 'normally open' and is closed when vacuum is applied to the actuator. The goth bypass actuation is the same as OE .... except quieter ... so it is 'plug and play' ... ;)

    You can check for bypass rattle, by putting a bit of pressure on the bypass valve linkage or shaft with a long screwdriver. Then listen for any changes in noise. A groaning sound could be the 2ndary air check valves ..... is the noise audible at certain points of operation (warm up) or all the time when running?
     
  7. Qavion

    Qavion F1 World Champ
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    #7 Qavion, Aug 22, 2016
    Thanks...

    So far, I think, I've only heard it during warm-up. Hope it's not an expensive sound ))
     

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