355 O2 Sensor Question | FerrariChat
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355 O2 Sensor Question

Discussion in 'Technical Q&A' started by BrandSB, Jan 30, 2010.

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  1. BrandSB

    BrandSB Karting

    Jun 11, 2008
    236
    Canton, Michigan
    Full Name:
    Steve
    #1 BrandSB, Jan 30, 2010
    Last edited by a moderator: Sep 7, 2017
    O.K. my Fabspeed header project is proceeding and I've just installed my new Bosch O2 sensors into the Quicksilver test pipes I'm including in the project. As seen in the photos below, the original cat O2 sensors were located well into the exhaust flow of the pipe. The new O2 sensors on the Quicksilver test pipes do not even drop below the circumerence of the pipe. It's odd because the QS pipes have an added spacer welded to the threaded bung which prevents the sensor from entering into the gas flow of the pipe. Any opinions as to whether this will negatively affect the sensitivity of the O2 sensor? I've always understood that the most direct O2 feedback loop is critical for the engine to make quick air-fuel adjustments (the '95's only have one O2 sensor per cat). It's hard to believe that Quicksilver would do something like this inadvertantly but this noticeable shift away from OE concerns me. Thoughts, comments? Anyone out there have QS test pipes with a similar configuration?
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  2. tech4ferrari

    tech4ferrari Karting
    Professional Ferrari Technician

    Jan 22, 2010
    234
    Mt Airy N,C
    Full Name:
    casey johnson
    #2 tech4ferrari, Jan 31, 2010
    they probably did that so that there would be less of a chance for the check engine light to come on, i know alot of tuners replacing cats with test pipes will add washers to o2 sensors taking them out of the exaust flow keeping the chance of the check engine light comming on to a minimum...that would be my guess as to why they did it that way.
     
  3. BrandSB

    BrandSB Karting

    Jun 11, 2008
    236
    Canton, Michigan
    Full Name:
    Steve
    #3 BrandSB, Jan 31, 2010
    Thanks for the reply Casey. Any idea why the check engine light would come one? Maybe because the sensor can't hold temperature in the unobstructed airstream?

    I'll give Quicksilver a call tomorrow and will try to get a difinitive answer.
     
  4. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,620
    The Brickyard
    Full Name:
    The Bad Guy
    #4 ernie, Feb 1, 2010
    It's because the 2nd sensor measures the O2 level after the cat. If it sees O2 levels that are too high it thinks the cat isn't doing it's job = check engine light.
     
  5. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    Dec 7, 2003
    16,476
    Winston Salem, NC
    #5 Ricambi America, Feb 1, 2010
    Luckily, yours is a 1995 single O2 car. You're 'less likely' to have CEL troubles.

    I ran test pipes in the past on my 348, and honestly, they lost their appeal quite quickly. Speaking from personal experience (this has nothing to do with Ricambi), I thought the gassy smell wasn't worth the supposed performance. I'm pretty sure high-flow cats flow within a small percentage of test-pipes, and more importantly, your clothes don't stink like Exxon after driving.

    I used to have test pipes on my car, and simply could not stand it.

    YMMV, IMHO, etc. etc.

    LOTS of 1995 F355 drivers have test pipes on their car, and are perfectly happy. I don't know if they have CEL issues or not, but I suspect with your O2 sensor pulled so far back, you have minimized the chances of CEL. You do however, maximize the chance that the O2 sensor is not doing its intended job to measure exhaust gasses.
     
  6. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    Dec 7, 2003
    16,476
    Winston Salem, NC
    #6 Ricambi America, Feb 1, 2010
    p.s. Looks like the mfg also angled the sensor so it intentionally points backwards and isn't bombarded with gasses. Clever trick.
     
  7. BrandSB

    BrandSB Karting

    Jun 11, 2008
    236
    Canton, Michigan
    Full Name:
    Steve
    #7 BrandSB, Feb 1, 2010
    Yeah I hear you regarding the downsides but I've got to give them a shot. I can always quickly revert back if they're too objectionable. Plus I'm learning soooo much about O2 sensors that I never knew before :)
     

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