AAV too small at cold start? | FerrariChat

AAV too small at cold start?

Discussion in '308/328' started by yelcab, Jul 10, 2024.

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  1. yelcab

    yelcab F1 World Champ
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    Nov 29, 2001
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    San Carlos, CA
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    Mitchell Le
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #2 Steve Magnusson, Jul 10, 2024
    Last edited: Jul 10, 2024
    Ehhh -- can you show the other side of the AAV body? Is this the adjustable type of AAV with the small nut and stud like this:

    Image Unavailable, Please Login

    I did readjust my ex-AAVs a time or two over the decades.
     
  3. yelcab

    yelcab F1 World Champ
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    how is it adjusted
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Are you saying that it does have the adjustment nut feature? If so, I just used a drill bit shank to put the shutter where I wanted it (maybe .156" or .188" -- I can't recall and no longer have my records), and loosened and retightened the nut. What is the symptom that you are trying to resolve? Just think the cold start RPM is too lowish?
     
  5. yelcab

    yelcab F1 World Champ
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    Yup, cold start too low.
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Are you sure that the AAV is closing when warm? A "dead" AAV would also give that symptom -- i.e., the AAV opening just stays constant, and, since it is all tweaked up for warm-running, warm-running is fine (even though the AAV is wrongly a little open), but no extra air is allowed in during cold start-up. Just something else to check...
     
  7. yelcab

    yelcab F1 World Champ
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    Yes, I removed it from the car, attach it to 12V battery, and it closes totally in about 10 minutes.
    Which is also a reason to not make the cold orifice totally too big, or it would take a long time to close up.
     
  8. yelcab

    yelcab F1 World Champ
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    Well, I tried adjusting it and it did not get a whole lot bigger. The adjustment rod is maxed out against one side of the eccentric hole and that is the max it's gonna be. I guess I might need a new one afterall.
     
  9. miketuason

    miketuason F1 World Champ
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    Just wondering since the orifice is so small, why is the hose connected to the AAV is so damn big why couldn’t be the hose the same size as the orifice?
     
  10. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #10 Steve Magnusson, Jul 11, 2024
    Last edited: Jul 11, 2024
    Mitchell's picture is at 60 deg F -- at 32 deg F (or lower) it will be more open. Also, you want all of the flow restriction to be in the "shutter" portion, not in the hoses nor the hose mounting nipple IDs (so different models using CIS with different AAV hose lengths get the same behavior with the same AAV) = pushes the Engineer to use a seemingly oversized hose.
     
    miketuason likes this.

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