Correct procedure to check vacuum | FerrariChat

Correct procedure to check vacuum

Discussion in 'Technical Q&A' started by G.Simpson, Sep 7, 2011.

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  1. G.Simpson

    G.Simpson Karting

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    Gary Simpson
    May sound like an easy question, but can someone tell me the correct way to check engine vacuum on my 98 355F1?

    I assume I should remove the vac hose from the base of the rear most throttle body on each bank and take a reading from that point, leaving the check valve in line and place.

    I assume the vacuum pump that provides brake assist will not matter in this case?

    How many inches of vacuum should be acceptable as normal?

    Thanks
     
    G.Simpson, Sep 7, 2011
    #1
  2. JeffBarber

    JeffBarber Karting

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    Very interesting, I just went throught the same ordeal, I'd be interested in answer. My showed 4 to 5 inches where you're talking about, 97 F355 GTS 80k miles.
     
    JeffBarber, Sep 7, 2011
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  3. G.Simpson

    G.Simpson Karting

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    Mine read about 5 inches as well. Seems way too low. I was expecting anywhere from 18 to 20 inches at idle, about 1050 rpm or so.
     
    G.Simpson, Sep 7, 2011
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  4. JeffBarber

    JeffBarber Karting

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    Does your's fluctuate/oscillate at all? Mine oscillates rapidly between 4 and 5 inches.
     
    JeffBarber, Sep 7, 2011
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  5. G.Simpson

    G.Simpson Karting

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    Yes it does oscillate, most likely due to intake pulses, mine is reading slightly higher, between 5 and 6 inches.
    I just found your other thread and am trying to follow along.
     
    G.Simpson, Sep 7, 2011
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  6. Mitch Alsup

    Mitch Alsup F1 Veteran

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    There really is no engine vacuum in the F355. Each cyclinder has its own individual vacuum.

    Brake assist is provided by a hydraulic system up under in the front left bonnet.

    My engine looks to run around 15-17 in-Hg in a fuzzy image I took years ago with manometers on each throttle body.
     
    Mitch Alsup, Sep 8, 2011
    #6

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