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Question about AAV

Discussion in '308/328' started by miketuason, Mar 11, 2022.

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  1. miketuason

    miketuason F1 World Champ
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    #1 miketuason, Mar 11, 2022
    The Auxiliary Air Valve when it’s open (cold) the orifice or the opening is about 4mm to 5mm for the air to go through. So, why is the the vacuum hose attached to it has a 19mm ID, is it more for air volume?
     
  2. moysiuan

    moysiuan F1 Rookie
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    #2 moysiuan, Mar 11, 2022
    Great question!
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #3 Steve Magnusson, Mar 11, 2022
    It's just to ensure that the valve in the AAV is what controls the airflow, not the pressure drop in the hose -- and Bosch designed it for being used on other marques so maybe not so necessary to be so big on Ferrari, but maybe more important on others that have very long AAV hoses. Are you sure about that 19mm ID size? My "I'm-not-going-to-check-it-off-hand-memory" is that it's more like 15~16 mm ID hose.
     
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  4. miketuason

    miketuason F1 World Champ
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    #4 miketuason, Mar 12, 2022
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #5 Steve Magnusson, Mar 12, 2022
    Ack!!! - You've proven once again, Mike, that my "I'm-not-going-to-check-it-off-hand-memory" is often wrong. ;)

    I went thru my files and found this picture of a 308QV AAV ...229 with a file name of "AAV cold..." so probably just out of the freezer (i.e., 0 deg F), but shows that the opening can be pretty large and the ID of the 19mm hose fitting isn't much larger:

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  6. miketuason

    miketuason F1 World Champ
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    #6 miketuason, Mar 12, 2022
    Well maybe that’s is the difference between having the AAV coming right out of a freezer and and an AAV that sits overnight with a 50deg F to 60deg F average temp. If that’s the normal opening size then maybe you’re right 19mm vacuum hose isn’t much.
     

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