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Megasquirt Pinout To Stock Ecu

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    Megasquirt Pinout To Stock Ecu

    Hey everyone, I have a few questions concerning megasquirt. I planned on making a breakout board that connects the DB37 connector and plugs straight into the ECU connector, just to have a clean and simple install. The board is going to have to vias that can be jumped to work for the narrowband and then I'm going to leave a connector on the edge to connect a wideband controller and signal wires. I'm also going to make a connector that converts the AFM to an intake air temp sensor, in case the pinout below makes no sense. I made a spread sheet of the pinout I made here: https://docs.google.com/spreadsheets...it?usp=sharing

    So obviously if something is wrong on the pinout let me know, but here are my questions:

    1) Does the megasquirt need a CAS? If so, isn't the signal inverse due to the wiring?
    2) What are the differences between the grounds specifically #28 compared to #6,#34,#55. I think #28 is a true engine ground just asking for clarification
    3) Where does the tach signal come from for the instrument cluster?
    4) What pin is used for the A/C input to increase idle & is there anything like this for the alternator?
    5) Does pin #2 on the Megasquirt need to be ground if nothing is connected or can it be left floating?
    6) Are the stock injectors high impedance?
    7) On the Ecu side there's only two connections for spark #51 & #52, so it likes look it runs in wasted spark I just need some clarification on this cause this makes the ignition confusing to me

    For clarification I'm using the MS3 V3 board. Here's the pinout I'm using: https://drive.google.com/open?id=0By...DFGcE1iTEN4LVET

    Thanks for any help! I would've posted this in the the tuning section, but it seems more pertinent to the M42
    Last edited by gespinal0301; 04-23-2017, 02:55 PM.


    My Daily Driven 318is

    #2
    Originally posted by gespinal0301 View Post
    1) Does the megasquirt need a CAS? If so, isn't the signal inverse due to the wiring?
    2) What are the differences between the grounds specifically #28 compared to #6,#34,#55. I think #28 is a true engine ground just asking for clarification
    3) Where does the tach signal come from for the instrument cluster?
    4) What pin is used for the A/C input to increase idle & is there anything like this for the alternator?
    5) Does pin #2 on the Megasquirt need to be ground if nothing is connected or can it be left floating?
    6) Are the stock injectors high impedance?
    7) On the Ecu side there's only two connections for spark #51 & #52, so it likes look it runs in wasted spark I just need some clarification on this cause this makes the ignition confusing to me

    For clarification I'm using the MS3 V3 board. Here's the pinout I'm using: https://drive.google.com/open?id=0By...DFGcE1iTEN4LVET

    Thanks for any help! I would've posted this in the the tuning section, but it seems more pertinent to the M42
    1. Yes, unless you're planning on triggering the coils in a wasted spark configuration by firing two coil drivers with one output.

    2. See below

    3. See below

    4. See below and no

    5. The shielding braids of the harness are grounded at G103 according to the ETM, all megasquirt ground pins are common to the board ground plane.

    6. I don't remember but probably, not hard to check.

    7. If you are seeing this, I believe your pinout is incomplete. I didn't look at it too closely.

    Here's some info from my MS2 M42 project;




    Last edited by varg; 04-23-2017, 03:53 PM.

    IG @turbovarg
    '91 318is, M20 turbo
    [CoTM: 4-18]
    '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
    - updated 1-26

    Comment


      #3
      Thank you! I saw that pinout, but I assumed that it was for the e36 since I saw the knock sensors. Let me look this over and read the mega manual a little more and I'll post it again. Looking at your pinout I noticed I forgot the heater relay for the O2


      My Daily Driven 318is

      Comment


        #4
        So after reading the pinout you provided pin 28 (ECU) should be connected to pin#2 since it contains the shielding for various sensors. I'm assuming since the CPS & CAS are magnetic they would be included in that list.

        I still don't understand the reasoning for the grounds that you picked. #43 makes sense since it's the grounding point for all the sensors so the voltage difference should be minimized by connecting the O2 sensor there as well. #28 is GND for all the electronics so shouldn't that be tapped for all the power ground that MS needs?

        Also, why connect the spares to #34 & #55?

        I feel like I'm overthinking a little too much haha


        My Daily Driven 318is

        Comment


          #5
          Since the MS circuits are on a common ground plane it doesn't really matter, there really isn't any risk for different potentials for our purposes. I just ordered it in a way that was neat for wiring purposes and covered all ground pins on the 88 pin connector. The adapter spreadsheet I posted a screen capture of is what I made as a reference for my adapter.

          The position sensors are both VR sensors on the M42, M44 has a Hall Effect cam sensor. The wiring polarity and trigger edge settings I posted were verified with a timing light and fixed advance.

          IG @turbovarg
          '91 318is, M20 turbo
          [CoTM: 4-18]
          '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
          - updated 1-26

          Comment


            #6
            Completely missed that in the previous post lol thanks for explaining that and Ill defintely come back for that once I have everything set up. Thank you once again!


            My Daily Driven 318is

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              #7
              Also, our tach signal is the 0-12V pulsed signal so all it needs is the jumper from JS0 to IAC1A correct?


              My Daily Driven 318is

              Comment


                #8
                6 yes, high impedance.

                t
                now, sometimes I just mess with people. It's more entertaining that way. george graves

                Comment


                  #9
                  Originally posted by TobyB View Post
                  6 yes, high impedance.

                  t
                  Thank you one more thing to check off the list lol


                  My Daily Driven 318is

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                    #10
                    So I've figured everything out for the most part, the updated pinout is here: https://docs.google.com/spreadsheets...it?usp=sharing
                    the
                    The last few things I need to figure out are

                    1) AC Input, for idle up control when it is switched on. Haven't found much information on this
                    2) Tach output, not sure if the signal can be ran straight to the tach without any internal mods


                    Thanks for all the help so far!
                    Last edited by gespinal0301; 04-26-2017, 08:57 AM.


                    My Daily Driven 318is

                    Comment


                      #11
                      The ETM is somewhat confusing on the subject of AC idle up. Page 6452-2 claims

                      When the Compressor Clutch is turned on, voltage is applied to pin 29 of the Motronic Control Unit. The Motronic Control Unit uses this signal increase idle speed to compensate for the increased engine load from the Compressor Clutch engaging.
                      This can't be true, because pin 29 is the ICV output. It also mentions that pins 85 and 86 should see voltage when the AC is turned on. 86 is marked AC Input, that will be what you want to use to tell the megasquirt to increase idle speed. It appears the ECU cannot disengage the compressor at high RPM, so it must be rated for such operation, or relying on the high pressure switch (435psi) to disengage the clutch if the engine RPM causes the pressure to rise too high.

                      Tach output straight from the MS board works fine.

                      IG @turbovarg
                      '91 318is, M20 turbo
                      [CoTM: 4-18]
                      '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
                      - updated 1-26

                      Comment


                        #12
                        So I think I have everything now, thank you again Varg! I just need to figure out some things for the boost solenoid, but besides that I should be putting it together mid July!


                        My Daily Driven 318is

                        Comment


                          #13
                          One lllllaaassstttt thing I read that some crank sensors need a 10k resistor for the CPS. Did you run into this issue? If anything I'll leave a jumper available for it just in case
                          Last edited by gespinal0301; 04-27-2017, 08:51 PM.


                          My Daily Driven 318is

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