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Motronic PWM Trip Computer Output

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  • Motronic PWM Trip Computer Output

    Thinking I'm going to try and get the trip computer working via a PWM output on the MaxxECU. Rather than try and scope Motronics output I plan to set a linear range against IDC and then tweak it over a few tanks of fuel so the computer tank average matches calculated average. Dmitri or any other Motronic gurus if you are listening, do you happen to know the PWM frequency that Motronic outputs?

    Panthero Coupé quattro 20vt
    Indigo ABY coupé
    Imola B6 S4 Avant

  • #2
    Jaap wrote here that the trip computer can also deal with 0 - 5V.

    Would be great if anyone would fix the problem with the trip coumuter and aftermarket engine Management.


    • #3
      Watching this closely since I'm about to invest in MaxxECU.
      If I can help in any way let me know, though I'm not good with electronics
      Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes


      • #4
        Any updates on this? I have my dash in with an instrument specialist to see if they can determine what signal it needs. Has anyone tried feeding an IDC output directly to the dash?


        • #5

          S2 Coupe 3B Project

          Ur quattro restoration

          S2 Avant

          Boost is the new rock and roll!


          • #6
            Simply feed 0-5V depending on IDC.
            On ecumaster this is super easy to do using a virtual output.


            • #7
              0-5V - to PWM or what ever?
              0V = 0 km/h
              4V = 2xxkm/h? :-)


              • #8
                It's not km/h it's for the fuel consumption. Set 0-5V vs injector IDC and then monitor and correct it until it is right.


                • #9
                  Originally posted by prj View Post
                  Simply feed 0-5V depending on IDC.
                  On ecumaster this is super easy to do using a virtual output.
                  I have been looking through the ECUmaster EMU classic SW. Some parts are still confusing to me. Like how to link a switch input to switch tables.

                  Do you know how to feed 0-5v PWM out from VEMS or MaxxEcu? All the outputs I see on those are 0-12v.
                  Also been studying the MaxxEcu MTune SW lately. Starting to understand it.

                  Can a General Purpose Output (grounding) be used to send PWM signal to trip computer?
                  Last edited by ChrisAudi80; 5th January 2018, 10:11.
                  '96 UrS6 auto PRJ chipped E85
                  '95 80Q AEB VEMS E85


                  • #10
                    I have a MAPECU3 piggyback unit. It can work as a datalogger.
                    One of the options it has, is intercepting KVF MAF signal, which is Hz, so DC can be (in)directly measured. Of course, it can also log MAP, TPS, RPM etc.

                    EDIT: Correct me if I'm wrong, but DC = PW * frequency.
                    If max injector PW is 25.5ms (100% DC) as set in VEMS, that means f is 100/25.5, right? Only 4Hz? Does not sound right.

                    If I got this right, a table with RPM vs MAP with DC as value would be good to know. If all three values are known then the output for fuel consumption is known.
                    A table in VEMS or MaxxEcu can be made.

                    VEMS has a secondary PWM out in alternate boost settings. It is a grounding signal, so should be safe for the board comp.
                    MaxxEcu same but better.

                    Any thoughts?
                    Last edited by ChrisAudi80; 7th January 2018, 14:58.
                    '96 UrS6 auto PRJ chipped E85
                    '95 80Q AEB VEMS E85


                    • #11
                      Just for context I’m trying to get the fuel consumption computer working with a Link G4 on my ADU. I think the principal is the same as for the other aftermarket ECUs. I have sought tech support from Link on this but as my ECU is a wire-in system they do not have the specialized knwowledge. They do a plug in ecu for the Audi TT but this uses CAN for the dash.

                      From PRJ’s M232 thread:
                      Originally posted by prj View Post
                      Fuel consumption - there is no need for PWM, simply run a 0-5V signal equal to IDC through a DAC.
                      DAC = digital - analog converter yes? Previously in this thread it was stated the fuel computer can accept 0-5v. So is a digital signal input needed after all and if so what should this signal look like?


                      • #12
                        You can run PWM with a 5V pullup or you can run a DAC, it's all the same.
                        Think - what happens to a PWM signal when you put a cap and a resistor on the input and then run it into an ADC?


                        • #13
                          OK, can use a 0-5v signal out from ECU, but if the ECU in question cannot do this, a Duty Cycle signal should work too, right?
                          I have ordered this .

                          Will use it to datalog:

                          TCU Shift point signal. Need to know if it is a table switch or variable voltage signal.
                          Fuel consumption signal (PW or DC, frequency) to Board comp and TCU.
                          inj DC or PW. To compare to above.
                          TPS signal from ECU to TCU. Should be possible to just splice into signal from TPS.
                          Gear selector signal. This is probably just for the starter relay interlock. I have the 97 TCU current flow diagram, but need to study this path more closely.

                          It looks like MaxxEcu Race is the standalone to go for. When the time comes, will have to talk with them in detail about custom wiring adapter.
                          '96 UrS6 auto PRJ chipped E85
                          '95 80Q AEB VEMS E85


                          • #14
                            Did you solve this?
                            I'm trying to get the boost gauge to work with my MaxxEcu without any success. Have tried PWM with +5V pull up but the numbers in the gauge just fluctuates randomly.