Vibration resonance sound. | FerrariChat
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Vibration resonance sound.

Discussion in '308/328' started by doggydoggen, May 26, 2023.

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  1. doggydoggen

    doggydoggen Karting

    Apr 25, 2023
    120
    Sweden Umea
    Full Name:
    Doger Karlstrom
    #1 doggydoggen, May 26, 2023
    Hello, i have a resonance/vibration in the cabin on my 308,, in about 3000 rpm, it is not pleasant, it sounds like the exhaust touching the frame, i have checked everything an it is ok, now i'm starting to think that the hoses from the aircon is touching somewhere it should not, anyone recognise this?
     
  2. Cennzo

    Cennzo Karting

    Jan 29, 2020
    111
    Sausalito CA
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    Vince Dattoli
    #2 Cennzo, May 26, 2023
    It makes that kind of noise in my 328 at about 4000 rpm, and I've yet to figure out what it is. I look forward to replies to this thread . . .
     
  3. doggydoggen

    doggydoggen Karting

    Apr 25, 2023
    120
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    Doger Karlstrom
    #3 doggydoggen, May 26, 2023
    it was the hoses, i have rereote the hoses and but a foam between chassis and hoses, but it is not 100% perfect,need to find out a good solution, the hoses is very stiff, old technology, steel braided hoses, you could probably change them to more flexible hoses, but gonna try to fix it with the original hoses.
     
  4. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    Brian Crall
    #4 Rifledriver, May 26, 2023
    Really common issue. A/C hoses going over the fuel tank bearing against the body work. The angle of the fittings at the compressor need to be readjusted. In a few cases I stuffed foam rubber between hoses and body work above fuel tank. Sometimes the correct angles prevent connection to the A/C service ports so they get adjusted wrong. I just change the angles after the A/C is charged.

    328 and 308 both do it but at different RPM. Flat crank V8s have rpm ranges of vibration and because of the different stroke they are in slightly different RPM ranges.

    Steel braided A/C hoses? Those are not original.
     
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  5. Cennzo

    Cennzo Karting

    Jan 29, 2020
    111
    Sausalito CA
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    Vince Dattoli
    #5 Cennzo, May 26, 2023
    Very interesting - thanks for this detailed response! I will have a look at those hoses today and hopefully get this sorted out.
     
  6. jmaienza

    jmaienza Formula Junior

    Jan 8, 2009
    628
    Massachusetts
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    Joe
    #6 jmaienza, May 26, 2023
    When I replaced my AC hoses there was some soft foam rubber around the AC hoses where they went above the gas tank and then into the forward area.



    Sent from my iPhone using FerrariChat
     
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  7. doggydoggen

    doggydoggen Karting

    Apr 25, 2023
    120
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    Doger Karlstrom
    #7 doggydoggen, May 26, 2023
    i assumed it was steel braided, with that i don't mean steel on the outside, steel in rubber, high pressure, so it seams impossible they are plain rubber.
     
  8. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    #8 Rifledriver, May 26, 2023
    Many, in fact most high pressure hoses do not use steel. No need. Steel braid on the outside is not for high pressure. It is for abrasion resistance.
     
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  9. doggydoggen

    doggydoggen Karting

    Apr 25, 2023
    120
    Sweden Umea
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    Doger Karlstrom
    #9 doggydoggen, May 26, 2023
    yes nowadays, but interesting that they used other material then steel in high pressure hoses in 1980, can you tell me what they used instead?, because im talking about hoses in the god old days, and in this case the compressor hoses on our old 308, not high tech nylon or kevlar hoses in 2023.
    that's why i said that they were stiff and it should be possible to change them to modern hoses with nylon or kevlar core.
     
  10. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    #10 Rifledriver, May 26, 2023
    Last edited: May 26, 2023
    Modern nylon?

    Its been in use reinforcing rubber since the 40's.

    Stiffness is one of the hallmarks of nylon. The difference between truck tires and RV tires is truck tires use nylon cord. RV tires use polyester usually because nylon is too stiff and makes RVs ride bad.

    We have been using it in tires for over 70 years because it is so strong.
     
  11. john a barnes

    john a barnes Formula Junior
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    Dec 19, 2018
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    John a Barnes
    #11 john a barnes, May 29, 2023
    Yes Sirs, I have the same Problem driving me nuts. I was going to add a 1/2 lb to the A/C anyway, so gotta take apart the Tubs.
     
  12. doggydoggen

    doggydoggen Karting

    Apr 25, 2023
    120
    Sweden Umea
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    Doger Karlstrom
    #12 doggydoggen, May 29, 2023
    i have trye some diffrent ideas, first don't add any foam or other isolation stuff between hoses and body panel, it will transfer some amount off sound/vibration, relocate hoses so you get about 10mm from body, on the tank you have a welded
    flat iron on the backside/side of the tank, the hoses i believe should be between this 2 welded peaces on the tank, put some isolation foam inside and leth the hoses lay on the tank, the tank is heavy and filled with gasoline so it acts like a vibration damper, the body don't.:)
     
  13. john a barnes

    john a barnes Formula Junior
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    John a Barnes
    #13 john a barnes, May 29, 2023
    Yeah, I get what yer saying. Suddenly it has to wait while I fix the Sahara TJ. Oy Vay, always something.
     

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