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Rotten eggs smell from high flow exhaust system

Discussion in 'Technical Q&A' started by mw575, Dec 5, 2003.

  1. mw575

    mw575 F1 Rookie

    May 30, 2001
    2,924
    Lake Oswego,Or
    Full Name:
    Martin J Weiner,M.D.
    Hate to be redundant since this is posted in gen F discussion but thought the technicians on the chat focus here.
    My 575 has a tubi and Stebro straight pipes.No problems for 2500mi (love the sound).However for the last few weeks whenever the throttle is hammered a hydrogen sulfide smell wafts into the cockpit.Then when just cruising the smell disapears.
    Here is serv.mgr explanation as possibility.
    By putting on a tubi one creates a high flow exhaust system so that the exhaust gases are exposed to the cats a shorter time thus less breakdown of noxious substances,When srt pipes are added to the system,2 silencers are removed further adding to the high flow since the silencers(mufflers) would have further restricted the flow and now it is an even higher flow exhaust.
    Of course this begs the question as to why now since this system has been on the car for the last 2500 miles???
    Any ideas?
     
  2. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,334
    I doubt your service managers explanation.

    I will assume that the 575 uses a 3-way cat. In such a cat, the lead element decomposes unburnt fuel into hydrocarbons and oxegnates, This process takes dozens of nanoseconds to less than a microsecond, then the second element recombines the hydrocarbons and oxegenates into water vapor and carbon dioxide. This process also takes dozens of nanoseconds to around a microseconds. Assume the rear element is 2" long, light travels at 1 foot in a nanosecond. The exhaust gasses would have to be traveling around 1% of the speed of light to pass through the catalitic element in less time than the catalist supports the chemical reactions.

    I can believe that the exhaust gassses are traveling in the one thousand MPH range (just below speed of sound in 1500 degree gas). However, this is 186*60*60 times slower than the speed of light. Nope, there is plenty of time for a well working catalist to perform its function where teh gass is flowing a less than the speed of sound (in that gas at that temperature).

    Even if the exhaust travels twice as fast as it used to, there is still plenty of time for the reactions.
     
  3. mw575

    mw575 F1 Rookie

    May 30, 2001
    2,924
    Lake Oswego,Or
    Full Name:
    Martin J Weiner,M.D.
    Mitch-
    I'm going to relate your post to the SM.
    Do you have any ideas as to the cause?
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,159
    Texas
    Full Name:
    Steve Magnusson
    575M exhaust items
     
  5. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,159
    Texas
    Full Name:
    Steve Magnusson
    mw575 -- Forgive me for asking the obvious, but is your problem with the windows up or down (i.e., cabin sealed or unsealed) or does it not matter? Are you also saying that they've already looked for mid-stream leaks (e.g., that clamped connection at the cat outlet)?

    That's wild with the pre-cat built directly into the exhaust manifold -- bet the price is frightening ;)...

    US Version 575M exhaust (per 1838/02)
     
  6. Verell

    Verell F1 Veteran
    Owner Consultant

    May 5, 2001
    6,951
    Groton, MA
    Full Name:
    Verell Boaen
    SWAGS:
    Rotton Eggs is usually due to unburned/partially burned fuel.
    I'm wondering if something's changed so that the air injection can't keep up w/the sudden flow increase, so there just isn't enough O2 to cmplete combustion.

    Alternatively, the EGI is becoming too rich & resulting in incomplete combustion.
     
  7. mw575

    mw575 F1 Rookie

    May 30, 2001
    2,924
    Lake Oswego,Or
    Full Name:
    Martin J Weiner,M.D.
    Steve,
    I have only smelled the odor with the driver's window open.Will try with window closed if it ever stops raining here in Or.Supposedly dealer checked and no leaks.
    Verell-If the egi was too rich wouldn't that be picked up by the computer? The computer read out states all systems normal.
    I may have to take off the straight pipes before FNA will seriously look into this under warranty.(The dealer installed the tubi when the car was purchased).When the SMgr called FNA the probable blame was put on the "ater market pipes". Big surprise!
     
  8. Sfumato

    Sfumato F1 Veteran
    Rossa Subscribed

    Nov 1, 2003
    9,529
    Llanfairpwllgwyngyll, Anglesey, Wales
    Full Name:
    Angus Podgorney
    Martin:
    Do you live where they reformulate gas in winter? That could be an issue as well with the smell. Or a bad cat/going bad.
    Mitch's explanation was much more detailed than mine...thank god.
    RFG with whatever they put in it can do this, especially since it is acute. How far into tank/tanks are you?? I live in TX, so we don't need cold weather fuel mixes here, nor does EPA cram oxygenated fuel up our spouts.
    Lee
    Or, now it smells and rides like a Lincoln Townhouse LOL

     
  9. 92_348ts

    92_348ts Formula Junior

    Jun 6, 2002
    282
    Boise, Idaho
    Full Name:
    Chris
    Martin- Confirming that you have had the Tubi/Stebro setup on the car for almost 2500 miles?

    The reason I ask is that I just put a Tubi/Stebro setup on my 348 (http://ferrarichat.com/forum/showthread.php?t=2609) and I am getting the exact same smell. I was hoping that it was just the new components burning off any contaminants, however the smell has persisted for the last two days.
     
  10. wax

    wax Four Time F1 World Champ
    Advising Moderator

    Jul 20, 2003
    41,749
    SFPD
    Full Name:
    Dirty Harry
    Would a change to Tubis somehow affect an Oxygen Sensor?

    (On other makes anyway), Oxygen Sensor should be the first thing checked with the Rotten Egg symptom.
     
  11. mw575

    mw575 F1 Rookie

    May 30, 2001
    2,924
    Lake Oswego,Or
    Full Name:
    Martin J Weiner,M.D.
    Lee,
    Yes they do reformulate the gas here in Oregon for the winter.The cats were supposedly checked and fine as are all systems according to the computer.
    '92 348ts-
    The car was bought new in april '03 with tubi installed.Driven 2.5 k miles=no smell.Then had the central resonator replaced with Stebro straight pipes and have driven another 2.3kmi when the smell business started.That would be about when the gas is winterized which may put credence in Lee's suggestion.
    I wrote to Dan P at Stebro who is "researching " the issue.
    Thanks for the feedback,.guys.Any other thoughts appreciated.
    Since I take the car to Santa Barbara in Feb I will prbably do nothing until I try the "California gas"
     

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