Low/uneven Idle vacuum - is this an "issue" ? | FerrariChat

Low/uneven Idle vacuum - is this an "issue" ?

Discussion in '348/355' started by Gottaloveit, Mar 15, 2018.

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  1. Gottaloveit

    Gottaloveit Karting

    Jul 12, 2012
    52
    Hey guys,

    Had occasion to hook up a gauge to the throttle related vacuum lines at the back of the engine (1994 2.7). Results surprised me but are they an "issue" ?.

    Have read about the low idle vacuum on these cars due to the individual throttle bodies etc, but was a bit taken aback to see 8inHg on the left bank and 5inHg on the right bank !!. The central vacuum line down to the vacuum canister was showing 7inHg.

    Is this normal or is it something I need to look at and get sorted. ?. What do we think.

    Car runs fine tho !.

    Cheers all.
     
  2. Challenge

    Challenge Formula 3

    Sep 27, 2002
    1,933
    PA
    Full Name:
    Kevin
    I'm no guru on the topic but 355's don't even pull enough vacuum to drive the brake booster. This is why it is driven off bank 2's cam shaft. Are you sure your gauge is accurate?
     
  3. salbrech

    salbrech Karting

    Dec 20, 2013
    103
    this pressure is normal on a ITB- motor, have the same readings on my F355, 5.2. On my car, with the vacuum cannistor charged on Idle only, its not even possible to open the secondary air injection valve.

    Ferrari on some ITB-V12 cars installed a cam driven vacuum pump, but I guess not on the F355. On the F355, the break booster runs with an electric motor driven oil pump. As far I know, the F355 is the only V8 with ITBs, all other V8 have common throttle bodies.
     
  4. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    12,661
    San Carlos, CA
    Full Name:
    Mitchell Le
    First versions of 355 (and 328ABS/348) all have Teves brake master cylinder with electric pressure pump with no booster assist.
    Later (97+) have Bosch master cylinder, and vacuum assist via a vacuum pump running off one of the cam shafts on 5-8 bank, because the engine vacuum is not enough to drive the boostetr.
     
  5. salbrech

    salbrech Karting

    Dec 20, 2013
    103

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