355 - SDL with test pipes | FerrariChat
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355 SDL with test pipes

Discussion in '348/355' started by bcar1, Aug 18, 2020.

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  1. bcar1

    bcar1 Karting

    Aug 2, 2017
    224
    NYC
    Full Name:
    Bob
    #1 bcar1, Aug 18, 2020
    I've had test pipes on a 97 355 for about a year with no issues. Prior to that the car had evoflow or hyperflow sport cats (not sure which brand) and has 3 green epoxy color cat ECUs- I had 1 minor SDL issue that was eventually resolved to the bypass and the drivers side inputs being switched. Today while driving in bumper to bumper traffic, which I basically never do in the car, I was idling/moving slowly in the car for about 3 minutes and I started getting a flashing red SDL.

    My thot was maybe at idle not enough exhaust is flowing through the pipes so heat builds up- I blipped the throttle to 2500/3000 rpm and it went away. 5 minutes later similar situation, I did the same thing, SDL went away, CEL came on. After I got home I checked the codes p1445/p1449.

    Anyone have any idea what's going on here? Is there any risk to driving the car with the SDL and test pipes? My understanding is with test pipes there should not be enough heat to cause any issues & without a catalyst you can't get the cycle of rich exhaust burning off on the catalyst etc.
     
  2. wbt

    wbt Karting

    Nov 28, 2014
    234
    New Zealand
    Full Name:
    Wayne
    #2 wbt, Aug 19, 2020
    Correct, unlikely to generate the heat required without cats to get a slow down light as there is no honeycomb for the excess fuel to burn off. You're getting codes for both left and right hand side slow down warnings which is interesting. Centre position indicates ok. Likely ECU or thermocouple faults but unusual you have both happening at once. Since you have test pipes maybe bypass the slow down light with a dummy load on the 2 main cats and put a good known cat ECU and thermocouple on the centre bypass. I would recommend checking the car for misfire and fuel mix causes as well though just to be sure.

    Those green cat ECU's are starting to fail quite regularly. I've replaced plenty.
     
  3. bcar1

    bcar1 Karting

    Aug 2, 2017
    224
    NYC
    Full Name:
    Bob
    #3 bcar1, Aug 19, 2020
    it seems unlikely both left and right would have failed simultaneously right? Is there a rich running condition that could have caused exhaust gas to be hotter? Seems wrong but trying to wrap my head around an explanation.
     
  4. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    13,621
    San Carlos, CA
    Full Name:
    Mitchell Le
    #4 yelcab, Aug 19, 2020
    This is a rare but possible condition of the SDL. It is detecting that the cats are too ... cold by reading a thermal couple signal below a minimum threshold. An operating cat actually raises the temperature at the thermal couple.

    Put the cats back, or fix the too cold exhaust.
     
  5. bcar1

    bcar1 Karting

    Aug 2, 2017
    224
    NYC
    Full Name:
    Bob
    #5 bcar1, Aug 19, 2020
    Got it that would make sense, I take it there's no way to raise exhaust temps at idle?
     
  6. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    13,621
    San Carlos, CA
    Full Name:
    Mitchell Le
    #6 yelcab, Aug 19, 2020
    A leaner combustion runs hotter. But, you need a stoichiometric sensor if you want to go down that path.
     

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