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Confirmed or not that you can remove cat ecu's from 2.7 car?

Discussion in '348/355' started by INTMD8, Aug 11, 2017.

  1. INTMD8

    INTMD8 F1 Veteran
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    I'm making a set of test pipes tomorrow and trying to decide if I want to keep the cat ecu's or not.

    I've read they can be unplugged from the motronic ecu's and you will have permanent sdl's but no cel?

    Correct or no?

    :D
     
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  3. Dave rocks

    Dave rocks F1 World Champ
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    Jim - add the TC bungs and keep them :)
     
  4. dantm

    dantm Formula 3

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    I had the ECUs but no probes so I made my own probes to get rid of the SDL and a permanent code that was bugging me.

    Did not try to see what happened if the ECUs were removed altogether.
     
  5. Dave rocks

    Dave rocks F1 World Champ
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    Oh Jim, you may / may not get a CEL, but you may get a bank shut down. Don't do it unless you can reliably fake the system out.
     
  6. INTMD8

    INTMD8 F1 Veteran
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    Yeah no problem to add the bungs and keep them, just thought if they can be deleted with no issues (bank shutdown or loss of power) I would pull it out.

    Guess it would be easier to leave the stuff in case I swap the cats back in.
     
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  8. F355Bob

    F355Bob Formula 3

    I have been running without thermocouples and cat ecu disconnected for years on my 2.7 No problem. I used to have banks shut down because ecu would go bad now I don't worry about it and no I am not worried about a cat overheating. If my car is running so crappy that it is dumping raw fuel into my cat to cause it to overheat, I think I could tell without having 1/2 the engine needing to shut down. The problem is weak spark on these cars and if you loose a plug you loose two. The cat ecu is Ferraris insurance against fouled plugs causing cat overheat.
     
  9. Drock28

    Drock28 Formula 3

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    doesn't Goth have those cat ECU simulators..?

    regardless.. if your current cat ecu's are functioning correctly.. just leave them in and weld bungs for the probes on the test pipes..

    as such with my car a 5.2 with no problems.. running test pipes..
     
  10. BeachBum

    BeachBum Formula 3

    #8 BeachBum, Aug 19, 2017
    Last edited by a moderator: Sep 7, 2017
    I've got a couple after market cats off my 348 for sale. I'm not sure what brand they are. They only have one bung. Only have a few thousand miles on them. Replaced with hyperflows.
    Image Unavailable, Please Login
     
  11. INTMD8

    INTMD8 F1 Veteran
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    Zero relevance but thanks
     
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  13. m.stojanovic

    m.stojanovic Formula 3
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    On 2.7, the bank shut down ocurres when the TCU, after the SDL warnings, switches on +12V to a certain ECU pin (can't remember the pin number now, I mentioned it in the earlier discussion on the TCU-s). No TCU, nothing to send the +12V so no ECU shut down.
     
  14. drbob101

    drbob101 F1 Rookie
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    This is news to me.

    On a 355, the SDECU has one signal line only. It transmits a voltage derived from the TC amplification and is a linear output from .5v to 5v. The main ecu interprets that signal and either does nothing, blinks a sdl or INITIATES a bank shutdown.

    The SDECU does not transmit a 12v signal directly. I am speaking of 355s here. The OP has a 355.

    There is a bias voltage in the signal line of 5v and if the sdecu is unplugged you will measure 5v on it. This should initiate bank shutdown as that will occur if installed at approx 3.5 volts.

    I'm not sure how some report unplugging sdecu and not getting bank shutdowns but it has been so reported. Possibly that is a 2.7 variation.

    Again, I am speaking about 355s here. 348d have different sdecu and wiring and possibly that is what you are referring to.
     
  15. m.stojanovic

    m.stojanovic Formula 3
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    Yes, I was talking based on how the TCU works on a 2.7 348 and assuming that 2.7 355 is the same. I might be wrong (is 2.7 355 using the same TCU as the 348?).
     
  16. drbob101

    drbob101 F1 Rookie
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    Correct. The sdecu are different. 2.7 and 5.2 , f355 use the same one though. 348 is different .
     
  17. BeachBum

    BeachBum Formula 3

    Now I've got a bank shut down. Usually when this happens I just disconnect the battery, let things cool down and reconnect and everything is fine . Not this time reconnect battery but still running on one back. Thoughts
     
  18. F355Bob

    F355Bob Formula 3

    The two times I lost a whole bank. One was bad cat ecu, other was bad ground on block after a major
     
  19. drbob101

    drbob101 F1 Rookie
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    Do you have a SDL or CEL?

    What model/year is your car?
     
  20. m.stojanovic

    m.stojanovic Formula 3
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    If it is a 355, the bank shut down can also be caused by a bad Thermocouple or loss of contact at its connector to the TCU. According to my bench test, the 355 TCU sends a "shut down" signal to the ECU as soon as the Thermocouple is disconnected from the TCU.

    A long discussion on the 348 and 355 TCU-s is here http://www.ferrarichat.com/forum/348-355-sponsored-bradan/537300-348-sdecu-pinout-wiring-diagram.html
     
  21. Dave rocks

    Dave rocks F1 World Champ
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    Bank shutdown comes at a certain temperature as stated in the WSM. I don't know what voltage correlates to that temperature.
     
  22. m.stojanovic

    m.stojanovic Formula 3
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    It is all in the thread I showed the link to. The ECU will shut down at approx. 4.8 V received from the TCU, created by the "hot" signal, amplified 100 times by the TCU, from the Thermocouple. The TCU also sends high signal by itself (~4.9 V) to the ECU when the Thermocouple is disconnected which, obviously, will also shut down the bank.
     
  23. johnk...

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    For the 355, shut down is at 1868 +/- 68 *F. 1868 corresponds to 4.2V.
     
  24. Dave rocks

    Dave rocks F1 World Champ
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    Thanks, John :)
     
  25. m.stojanovic

    m.stojanovic Formula 3
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    You are right, 4.2 V shut down. I made a mistake when I said "shut down at approx 4.8 V". I meant to say approx. 3.8 V which is also wrong as it is actually the SDL range. In any case, the TCU will send 4.9 V to the ECU with the Thermocouple disconnected, way above the shut down voltage.
     
  26. drbob101

    drbob101 F1 Rookie
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    Exactly. Which is why I'm left scratching my head on how some report the just disconnect the sdecu with no issues.
     
  27. m.stojanovic

    m.stojanovic Formula 3
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    The 4.9 V are sent to the ECU in the case when the TCU is still connected to the ECU but just the Thermocouple is disconnected from the TCU. I don't know what the 355 ECU (2.7 or 5.2) does when the TCU is disconnected from it. I know that the TCU, on ignition switch-on, sends a fixed 0.4 V to the ECU which then starts rising when the engine is started. It is probably this "baseline" 0.4 V that signals to the ECU that the TCU is present (or not, if there is no 0.4 volt to start with).
     

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