355 - Why gets one cat hotter than the other? slow down | FerrariChat

355 Why gets one cat hotter than the other? slow down

Discussion in '348/355' started by yvesolution, Jun 26, 2019.

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  1. yvesolution

    yvesolution Karting

    Apr 26, 2010
    182
    Cabo Verde
    Gentlemen,

    My 1995 2.7 355GTB is causing headaches, even the mechanic (Ferrari workshop since the 50s) doesn't
    know what to check!

    He did this year a cambelt change when he found a few things he thought they would cause the difference in heat... the right side cat shows 340°C and the left side 500°C then of course the slow down light comes on immediately :-(

    he replaced the simmering of the crankshaft

    the cams were on their correct position, but the crankshaft wasn't - he changed it to factory setting

    he changed the small motor that regulates the idle, as well as the lambda cable (it was bend)

    he found out the the small plastic tubes (bypass tubes) that feed the throttle bodies with air were in bad shape, those were replaced as well...

    the car has a Capristo exhaust, original remanufactured headers and sports cats in the original housings

    (The Vescovini are of the newer type)

    it has cost me so far (this season and last 10k€ without haven driven it :mad: I'm more than fed up!

    What can we do?

    :(
     
  2. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,484
    Sydney
    Full Name:
    Ian Riddell
    #2 Qavion, Jun 26, 2019
    Last edited: Jun 26, 2019
    Is this based on pyrometer/infra red readings?

    Does the car feel like its running normally? Has the O2/lambda sensor been replaced? Are there any unusual trends regarding fuel trims?


    Has he tried interchanging any engine sensors left/right?

    What do the spark plugs look like?
    Has he inspected the cat? Sometimes recores fail prematurely.

    What codes is the ECU generating?
     
  3. yvesolution

    yvesolution Karting

    Apr 26, 2010
    182
    Cabo Verde
    Hello Ian,

    what do you mean by "Are there any unusual trends regarding fuel trims?" ?

    I think he reads it with infra red

    Car has new spark plugs! He interchanged the ECU's last season, without much effect

    I don't remember on which cylinder bank it started in 2017, but it seems to me that I saw in the last season both lights come on (not at once)

    Cats (100 Cell) were remanufactured by a german company that work for Audi Motorsport - apart from that we had the CEL lights come on even before
    with spare cats
     
  4. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,484
    Sydney
    Full Name:
    Ian Riddell
    You would have to look at the video for further information. The videographer goes into more detail than I ever could :p It helps identify faulty components.

    I was thinking a fuel/air imbalance may lead to a hotter exhaust. I don't know if your technician has compared MAF or O2 readings on the two engine banks or tried swapping these sensors.

    Changing spark plugs may be getting rid of vital evidence.
     
  5. drbob101

    drbob101 F1 Rookie
    Owner

    Nov 26, 2012
    3,814
    Tinton Falls, NJ
    Full Name:
    Bob Ferraris
    Leaky valves, leaky injectors , hot cylinder.
     
  6. johnk...

    johnk... F1 World Champ
    Owner

    Jun 11, 2004
    10,628
    CT
    Full Name:
    John Kreskovsky
    This is the second thread in a week where someone has reported spending considerable money on a car with mechanics that can't figure out what the problem is. Makes me wonder about the qualifications of the mechanics. My suggestion is take the car to a different shop.
     
    WATSON likes this.
  7. Ferrarium

    Ferrarium F1 Veteran
    Rossa Subscribed

    Jul 28, 2018
    5,624
    Central NJ
    Full Name:
    Eric
    They have all turned into remove and replace jockys. No one can diagnose anymore. It's wide spread.

    Sent from my LM-Q710(FGN) using FerrariChat.com mobile app
     
    carnutdallas likes this.
  8. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    12,661
    San Carlos, CA
    Full Name:
    Mitchell Le
    The car has individual ports for exhaust gas analysis. Hooking up the right tool (which I don't have) will tell you which cylinder is running rich. From that information, further troubleshooting will tell you if ...

    1. Bad spark plug (my case)
    2. Bad compression (compression check)
    3. Leaky injector (send out to test)
    4. Bad ignition wires (measure resistance, or replace with another wire)
    5. Bad injector wiring (oscilloscope will tell)
    6. Fuel regulator problems (measure its fuel pressure at the rail)
    7. Bad O2 sensor (oscilloscope on its output)
    8. Bad TCU or bad thermocouple (swap side to side)

    500C is not enough to throw a flashing SDL, I don't think.
     
  9. SoCal1

    SoCal1 F1 Veteran
    Owner

    Jun 14, 2011
    8,562
    SoCal LA/OC/New Mexico
    Full Name:
    Tim Dee
    355 throttle bodies and those air covers leak like an old man drinking too much beer
    TB calibration is needed on so many of these cars

     
  10. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    12,661
    San Carlos, CA
    Full Name:
    Mitchell Le
    You would know all about this, wouldn't you?
     
    SoCal1 likes this.
  11. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    12,661
    San Carlos, CA
    Full Name:
    Mitchell Le
    Oh on this car, there are two coolant temp sensors at the rear of the water jacket, one for each bank. It's probably time to change them both or at least check their functionality. The individual ECUs use these signals to determine rich/lean running. Conceivably, one bad temp sensor can ruin the mix on that bank.
     
  12. SoCal1

    SoCal1 F1 Veteran
    Owner

    Jun 14, 2011
    8,562
    SoCal LA/OC/New Mexico
    Full Name:
    Tim Dee

    My TB need to be beyond perfect, Im silly like that LOL
     

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