355 - F355 2.7 Left & Right Motronic ECU Pin Function Variation | FerrariChat
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355 F355 2.7 Left & Right Motronic ECU Pin Function Variation

Discussion in '348/355' started by Qavion, Jul 17, 2021.

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  1. Qavion

    Qavion F1 World Champ
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    Ian Riddell
    #1 Qavion, Jul 17, 2021
    The Left & Right Motronic ECU's on a F355 are interchangeable. I assumed the pin functions would remain the same on both sides (although not necessarily used on a particular side). However...

    Pin 21 on the LH ECU controls the exhaust bypass valve. Pin 21 on the RH ECU controls the secondary air system. Therefore, something must be telling the ECUs in which position they are, and changing their behaviour. On aircraft, it can be done with "pin programming". i.e. certain pins on the computer backplugs are earthed. On the LH Motronics ECU, I see that pin 54 is earthed, but not on the RH ECU.

    Would anyone know if this pin 54 is a "program pin"? I haven't seen a 2.7 ECU pinout recently.

    Thanks!
     
  2. yelcab

    yelcab F1 World Champ
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    Mitchell Le
    #2 yelcab, Jul 17, 2021
    I know that you can swap the ECU left to right and they would work so internally they are the same. The difference must be in the wiring outside the box so it would make perfect sense they use a pin(like 54) to tell the ECU which side it is supposed to work on.

    These are questions we normally would pose to .... someone like you.
     
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  3. Qavion

    Qavion F1 World Champ
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    #3 Qavion, Jul 17, 2021
    :D

    Usually I can figure out how the various bits are hooked up together (given enough time), but the internals of these boxes are a complete mystery. On top of that, my 2.7 wiring knowledge is a bit rusty. I had to be reminded that the Left ECU controlled the bypass valve. On the 355, the ECU "extra" functions seem to be shared between the ECUs. On other Ferraris, the RH ECU seems to be loaded up with a majority of tasks.
     
  4. johnk...

    johnk... F1 World Champ
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    #4 johnk..., Jul 17, 2021
    Yes, the 2.7 ECUs must all be programed to drive the secondary air system or the by pass system. Something has to tell them which system they are connected to. Kind of like hooking up a smart TV and telling it HDMI 1 is the cable box and HDMI 2 is the DVD player (if anyone has those anymore). ;)
     
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  5. SoCal1

    SoCal1 F1 Veteran
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    Tim Dee
    #5 SoCal1, Jul 17, 2021
    Using "diff" and tools in the batronix tool chest I have compared R - L, ECUs on several cars.
    I can up with no difference between the two. Must be something in the wiring.

    Also wondered about this same deal on the bypass but never pursued further it as I don't run the bypass valves.

    :)
     
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