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M42 ECU Conversion: Link G4X / E36X

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    M42 ECU Conversion: Link G4X / E36X

    I am going to document my ECU conversion as it progresses over the next few months and share as much info as possible. While the M42-specific stuff won't be useful to all that many people since it's still sort of the red-headed step child of the E30 world, I think that a lot of the methodology, wiring harness design and connector part numbers will be of interest to people.

    First, which ECU am I going to be running? It is the BMWLink E36X, which is a Motronic form-factor version of Link's G4X XtremeX product. The G4X line was released around the beginning of 2019 and is their current latest-and-greatest platform. The XtremeX is the 2nd highest-tier ECU in that line. As far as "enthusiast" grade ECUs go, it is one of the better ones out there spec-wise, with AEM Infinity products being IMO the main competitor (not that it matters...Motronic has an 8 bit MCU running at 1MHz...basically everything on the market now runs 100-200MHz and on 16 or 32 bit cores).
    E36X ECU: https://dealers.linkecu.com/E36X_2
    G4X XtremeX specs: http://linkecu.com/documentation/Xtr...InECUSpecs.pdf

    These seem to retail for $1000-1100 at US dealers. That is VERY affordable for a quality aftermarket ECU. It is still what I'd consider an enthusiast-grade ECU, although plenty of racers use Link. "Real" motorsport-grade ones usually start at $4000 as a bare minimum, and have a ton of features that I have no need for (the M42 is a very simple engine compared to modern performance engines). Even better, it uses the same 88 pin connector as the M42's Motronic 1.7 ECU, so I really just need to move some terminals around and add new wires for the features I will add. It was a close call between this and the AEM Infinity 506, but the AEM ECU had a top-entry connector that I disliked since it would not work well with the factory ECU mount location, and it would require me to either use external ignition coil drivers, or change over to newer ones with built-in drivers (which would have been fine, but a bit more wiring work). I only recently became aware of the E36X, and it checked all of the boxes I cared about. For the M20 folks out there, the 88 pin connector used by M1.7 can be bought new at a number of places (quite a few motorsport ECUs use it as it turns out), and it uses the same terminals as the 55 pin connector on M1.3, so you could actually swap it right onto your harness if you get the terminal extraction tools.

    Regarding connectors and terminals, I will try to keep this post updated with part numbers as I accumulate them. Nearly every connector on our wire harnesses is a commercially available part from TE/Amphenol, from their various "Timer" series. The Motronic connectors use Micro Timer 1 and Junior Power Timer terminals, almost the entire rest of the harness uses Junior Power Timer terminals and housings, and (at least on the M42) the ignition coil connectors use Standard Power Timer terminals. You'll note that the technical drawings/datasheets for these have a zillion different variants. Most are unavailable, and the ones below were among the few that were both the correct type and still available on the web. This applies to all of the terminals listed below. BMW also has PNs for all of them, but they also mark them up heinously, so I only list those when it's the only option.

    COMMON TERMINALS / CONTACTS
    • Micro Timer 1 female terminals: TE PN 929952-1 (for 0.5-1.0mm^2 wires)
      So far this is the only problematic one...it is very likely out of production, and there is only one place that I have found which still stocks them. Micro Timer 2 & 3 terminals won't work in the Motronic connector as far as I can tell. I bought way more than I needed so as to have spares, and I got them here:
      https://www.onlinecomponents.com/te-...-10530804.html
      I have also seen PN 929927-1, which takes 0.2-0.5mm^2 wires, available at a few places in the UK.
    • Junior Power Timer female terminals: TE PN 927771-3 (for 0.5-1.0mm^2 wires), 927768-3 (for 1.0-2.5mm^2 wires)
      Used on the larger Motronic connector terminals, and nearly everywhere else in the harness where a rectangular housing is found.
    • Standard Power Timer female terminals: TE PN 927831-2 (for 0.5-1.0mm^2 wires), 927837-2 (for 1.0-2.5mm^2 wires)
      These are used on the M42's ignition coils, as well as in the relay sockets up on the firewall.
    • 2.5mm round male terminals: TE PN 929963-1 (for 0.5-1.0mm^2 wires), 929964-1 (for 1.0-2.5mm^2 wires)
      Used in many of the same places listed for the female terminals below.
    • 2.5mm round female terminals: TE PN 929970-1 (for 0.5-1.0mm^2 wires), 929971-1 (for 1.0-2.5mm^2 wires)
      At least on the M42, these are used in the AFM connector and O2 sensor connector, C101, diagnostic plug, as well as in various places in the chassis wiring.
    COMMON CONNECTOR HOUSINGS
    • 2 position compact receptacle, Junior Power Timer (JPT): TE PN 1-825414-5
      Used on the M42's fuel injector sub-harness. There is another PN, 826008-5, which looks similar but will not work on the injectors. It lacks the cut-out needed to clear the injector body, so don't buy that one.
    • 2 position receptacle, JPT: TE PN 827551-3
      This one is on the ICV, oil pressure switch, temperature gauge sender and some other places.
    • 3 position receptacle: TE PN 1-827578-1
      This is found on the M42 TPS, the M20 ICV, and a few other places.
    • 7 position round connector housing. The TE parts are not available, but BMW parts dealers seem to have them.
      Male housing: BMW PN 12521718125
      Female housing: BMW PN 12521718126
      Female housing lock ring for panel-mounting: BMW PN 12521718127
      90° rubber boot: BMW PN 12521737944
      The male & female housings are used on the M42's AFM connector, and on the M20's fuel injector harness connector. I can't find the PN for the straight boot at the moment.
    • Other JPT connectors: Search around online for Junior Power Timer connectors and you'll see a bunch of the other ones with 2-7 positions. There are really too many to list here since, at least for this project, I don't need them all.
    • 88 pin "Motronic" connector, with a few places that I found it for sale. Not cheap, and you could probably find a hacked-off one on eBay for a lot less (just de-pin it and you are good to go). M42 owners don't really need to worry about this since we already have one!
      https://prowireusa.com/p-2487-88-way...ector-kit.aspx
      https://www.automotiveconnectors.com...-assembly.html
      https://www.msel.co.nz/epages/motors...ucts/CONAMP88K
      https://racecal.co.uk/products/bosch...ctor-terminals
      A catalog for the 88-pin series of plugs: https://www.dalroad.com/wp-content/u...connection.pdf
    To crimp the terminals, you will want to get some decent crimpers. There are generic ones out there that work reasonably well, although they don't make the crimps as nicely as the factory did. Although I use different ones, these look like cheap ones that would work well with all of the terminals above:
    https://www.amazon.com/IWISS-Barrel-...dp/B07476C1LD/
    Personally, ratcheting ones are a lot more pleasant to use and this looks like a decent cheap setup:
    https://www.amazon.com/IWISS-Ratchet...dp/B08DRCRRCQ/

    For terminal extraction, this is the kit that I have. It has many more than are needed for this connector system, but I have lots of projects so it's fine for me. There are a bunch of cheaper copycat kits of this out there now, and they are all just as good. Don't buy any of the really cheap sets that look like a bunch of keys on a ring...they are not going to work well at all.
    https://www.amazon.com/Performance-T...dp/B00EDEEICA/


    I am working out the initial plans for the wiring harness modifications, and it is all still pretty rough since Link tech support needs to get back to me on a couple of questions, and I need to decide which new features actually matter enough to add. I'll post up a big table of the stock & new pinouts for things when I finalize it in the next week or two. Additionally, some of you may recall the big full-color complete M42 wire harness drawing I made a while back. I'll be making another one of those to fully document the new and improved one.

    To finish, as if there is not enough to read already, here is the list of "improvements" I plan to incorporate with this ECU:
    1) Dual knock sensing. The M42 block already has 2 threaded bosses for knock sensors which were added in the E36, so I just need to buy them and bolt them on (plus add wiring).
    2) Full sequential injection. Motronic 1.3 & 1.7 were set up to fire the injectors in two groups. I will be adding the necessary wiring to fire all of them individually.
    3) MAP-based load measurement. No more AFM (or in my case, MAF).
    4) Closed loop feedback using a wide-band O2 sensor.
    5) Traction control, or at least limited traction control. I can pull wheel speed signals from the ABS unit, and the ECU can do some limited torque management without an electronic throttle. Call E-throttle 5b...I may look into some variant of this if I have enough IO's left.
    6) M50 ICV. This should lead to a nicer idle than the M42's very basic PWM valve.
    7) Logging oil pressure & temperature, fuel pressure & exhaust gas temperature (all 4 cylinders individually, using an external TC DAQ via CAN).

    That's it for now. I'm going to take a break from thinking about this and go relax for the rest of the evening!
    Last edited by bmwman91; 01-01-2021, 07:44 PM.

    #2
    I can't wait for this. In regards to crimpers, I used this one https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 as after much reading, too many negatives. The chinese brand IWISS models are cheap and if you need a very strong crimp, might not be the right tool. This set has die sets as well that can be added for future project, which I know will always in your horizon. I had to do one of my COP connecters and opted for the better quality tool .
    Alex 88 m5 | 91 318is | 19 Subaru Ascent
    BMW Tool Rentals & Fender Roller

    Comment


      #3
      hey not dissing the M42 but traction control?
      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

      Comment


        #4
        Originally posted by digger View Post
        hey not dissing the M42 but traction control?
        Ha yeah I had the same thought, but the rear can get a little squirrely in corners when I am heavy on the throttle (even with the Wavetrac and stupid sticky tires). I used to be super anti-TC, until owning newer cars that had it and finding it to be pretty handy from time to time. Aside from that, the ECU has the TC inputs and capability, so if I am going to go to the trouble of customizing the harness and tuning everything, I am going to take advantage of as much capability as possible. It's all a big "hey, why not?" project anyway!

        Comment


          #5
          Originally posted by bmwman91 View Post

          Ha yeah I had the same thought, but the rear can get a little squirrely in corners when I am heavy on the throttle (even with the Wavetrac and stupid sticky tires). I used to be super anti-TC, until owning newer cars that had it and finding it to be pretty handy from time to time. Aside from that, the ECU has the TC inputs and capability, so if I am going to go to the trouble of customizing the harness and tuning everything, I am going to take advantage of as much capability as possible. It's all a big "hey, why not?" project anyway!
          i'm thinking about upgraing my ECU but im always in the keeping things relatively simple first off and expand later camp, plus i'm sceptical that medium level ECUs would come close to OEM for things like knock, traction control, launch control etc. Things are probably better these days
          89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

          new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

          Comment


            #6
            Originally posted by digger View Post

            i'm thinking about upgraing my ECU but im always in the keeping things relatively simple first off and expand later camp, plus i'm sceptical that medium level ECUs would come close to OEM for things like knock, traction control, launch control etc. Things are probably better these days
            I am looking forward to getting TC dialed in on the MS, see how effective it actually is, because I too am a little skeptical.
            I bet it is going to come down to a decent amount of messing around before it is decent though.

            Comment


              #7
              Originally posted by digger View Post

              i'm thinking about upgraing my ECU but im always in the keeping things relatively simple first off and expand later camp, plus i'm sceptical that medium level ECUs would come close to OEM for things like knock, traction control, launch control etc. Things are probably better these days
              Yes, I am also in the skeptic camp when it comes to aftermarket ECUs, particularly the less expensive ones. Bosch and BMW employ hordes of engineers whose entire job is developing systems that idle smoothly, make throttle transitions feel well controlled and ensure maximum reliability, and they can fund whatever salaries and equipment are needed to do it. I am not sure if I know of a single person running a stand-alone ECU who has gotten it run as well as stock in terms of idle and "around town" driving. At the same time, most guys I know with aftermarket ECUs are racing the cars and are mostly interested in max performance tuning. Given how much Jay over at Sssquid was able to adjust idle quality via fuel & ignition adjustments, as well as a bunch of "undocumented" filtering constants in a 30 year old ECU, I am reasonably confident that he & I can get this to drive really well.

              My high-level plan for now is to get this all wired and sorted out, to the point that the car will at least start & idle so that I can be sure that there are no electrical issues, swap the current harness & ECU back in, drive out to Kansas City and then put the heavily modified harness & Link ECU in for live tuning. I wanted to get out that way to visit him and Metric Mechanic last spring, but we all know how 2020 wound up going. Now I have a practical reason to get out there too.

              Anyway, if it ends up being the case that the Link ECU just won't run the car nicely, I'll just yank it all out and sell it. There's probably someone putting a racecar together who would like it. This is why I am keeping separate the harness that I completely cleaned & rebuilt earlier this year, so that I can just swap right back to stock if things do not work out to my liking. One of my friends who tracks his Miata swapped over to a MS3 PNP system a couple of years ago, and other than the idle not being as good as stock, he loves the improvement in throttle response and aside from low-throttle gremlins, he really likes how it drives. I am not sure if he worked at all with a professional tuner, either.

              I am going to take my sweet time with this since I have other stuff going on in life, so it'll probably be at least spring 2021 by the time I am ready to try to run it for the first time. But, hopefully you and others who are on the fence about a new ECU will have enough info to decide if this (or some other) system is a good choice.

              Comment


                #8
                Originally posted by JehTehsus View Post

                I am looking forward to getting TC dialed in on the MS, see how effective it actually is, because I too am a little skeptical.
                I bet it is going to come down to a decent amount of messing around before it is decent though.
                Did you tap into the VR sensors for the existing ABS system, or are you using some other method of input? I plan to tap into the VR's with a custom dual MAX9926 board I'll design.

                Comment


                  #9
                  Originally posted by bmwman91 View Post

                  Yes, I am also in the skeptic camp when it comes to aftermarket ECUs, particularly the less expensive ones. Bosch and BMW employ hordes of engineers whose entire job is developing systems that idle smoothly, make throttle transitions feel well controlled and ensure maximum reliability, and they can fund whatever salaries and equipment are needed to do it. I am not sure if I know of a single person running a stand-alone ECU who has gotten it run as well as stock in terms of idle and "around town" driving. At the same time, most guys I know with aftermarket ECUs are racing the cars and are mostly interested in max performance tuning. Given how much Jay over at Sssquid was able to adjust idle quality via fuel & ignition adjustments, as well as a bunch of "undocumented" filtering constants in a 30 year old ECU, I am reasonably confident that he & I can get this to drive really well.

                  My high-level plan for now is to get this all wired and sorted out, to the point that the car will at least start & idle so that I can be sure that there are no electrical issues, swap the current harness & ECU back in, drive out to Kansas City and then put the heavily modified harness & Link ECU in for live tuning. I wanted to get out that way to visit him and Metric Mechanic last spring, but we all know how 2020 wound up going. Now I have a practical reason to get out there too.

                  Anyway, if it ends up being the case that the Link ECU just won't run the car nicely, I'll just yank it all out and sell it. There's probably someone putting a racecar together who would like it. This is why I am keeping separate the harness that I completely cleaned & rebuilt earlier this year, so that I can just swap right back to stock if things do not work out to my liking. One of my friends who tracks his Miata swapped over to a MS3 PNP system a couple of years ago, and other than the idle not being as good as stock, he loves the improvement in throttle response and aside from low-throttle gremlins, he really likes how it drives. I am not sure if he worked at all with a professional tuner, either.

                  I am going to take my sweet time with this since I have other stuff going on in life, so it'll probably be at least spring 2021 by the time I am ready to try to run it for the first time. But, hopefully you and others who are on the fence about a new ECU will have enough info to decide if this (or some other) system is a good choice.
                  you shouldn’t have any trouble getting the basics right so it drives right from seat of pants.

                  Even my v500 from early 2000’s drives fairly nice. I’m looking for the following improvements / added functionality
                  - dual channel WB closed loop with LT/ST learning
                  - better injection timing control
                  - better tps resolution
                  - better CTS compensation table
                  - better fuel modelling
                  - maybe knock control
                  - fuel pressure sensor
                  89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                  new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                  Comment


                    #10
                    It seems that Link and their dealers have a 15% Black Friday sale going on. The E36X is now on sale for $845 from the guy in Arizona whom I got mine from (and he's got them for $100 less than anywhere else even before the sale).
                    https://panicmade.com/link/p/e36linkx

                    I have no affiliation, nor do I get a kick-back if anyone buys one...I just wanted to give a heads up since this is a pretty good deal.

                    Comment


                      #11
                      Originally posted by bmwman91 View Post

                      Did you tap into the VR sensors for the existing ABS system, or are you using some other method of input? I plan to tap into the VR's with a custom dual MAX9926 board I'll design.
                      I've got 4 hall sensors I am seriously considering fabbing up a bracket for. I may, however use the two VRs on the front and two halls on the back, because the rear wheels will be much easier to mount the sensors to. I don't have 4 spare VR inputs to the ms... but I do have 2, and 2 other non VR frequency inputs.

                      Once I 5 lug swap I am going hall all around, but the exact sensor will likely be dictated by the ABS unit.

                      Comment


                        #12
                        Originally posted by JehTehsus View Post

                        I've got 4 hall sensors I am seriously considering fabbing up a bracket for. I may, however use the two VRs on the front and two halls on the back, because the rear wheels will be much easier to mount the sensors to. I don't have 4 spare VR inputs to the ms... but I do have 2, and 2 other non VR frequency inputs.

                        Once I 5 lug swap I am going hall all around, but the exact sensor will likely be dictated by the ABS unit.
                        Well, if it will be a little while before you are going to implement it, I might have you covered. I plan to design up a small board with 2 x MAX9926 (dual VR conditioning IC) chips that will take the 4 ABS VR inputs and provide a nice 5V TTL output to the ECU since it also does not have 4 spare VR inputs. I actually spent a few hours this weekend with the oscilloscope doing some experiments on the ABS unit, and the spare MAX9926 board I had from a different project looked like it was working perfectly with the stock wheel speed sensors. As far as tapping into the signals, I think that I will de-pin those 4 wires from the ABS plug, cut the terminals off, and then crimp new ones on to hold both the original wire and the new "taps" together. They are just TE JPT contacts. The other option is butt splices, but I'd prefer not to use any of those.

                        Comment


                          #13
                          Originally posted by bmwman91 View Post

                          Well, if it will be a little while before you are going to implement it, I might have you covered. I plan to design up a small board with 2 x MAX9926 (dual VR conditioning IC) chips that will take the 4 ABS VR inputs and provide a nice 5V TTL output to the ECU since it also does not have 4 spare VR inputs. I actually spent a few hours this weekend with the oscilloscope doing some experiments on the ABS unit, and the spare MAX9926 board I had from a different project looked like it was working perfectly with the stock wheel speed sensors. As far as tapping into the signals, I think that I will de-pin those 4 wires from the ABS plug, cut the terminals off, and then crimp new ones on to hold both the original wire and the new "taps" together. They are just TE JPT contacts. The other option is butt splices, but I'd prefer not to use any of those.
                          Let me know, I am not sure when I will get to it. If I haven't I'm open to the idea.

                          Comment


                            #14
                            Here's an update for today, since I had a chance to do some poking around with the wheel speed signal sensors and a $20 eBay ABS computer. It turns out that bench-testing these things is not simple. They have extensive fault detection routines that run at start-up, and in the event of a fault they will basically not power themselves up enough to do any sort of meaningful testing. I'd have to connect some dummy relays and resistors to mimic the ABS pump. So, other than that I just used this thing to trace out the input circuitry for the wheel speed sensors and make sure that nothing there might get upset if I tapped into the signal lines externally.




                            I did pull the cover off of the one in the car and probed it with the rear wheels lifted and the engine idling in gear. The 16 pin DIP IC in the middle is the signal "conditioner" that takes the VR sensor signal and turns it into a 5V TTL signal. The 3rd pin in from each corner is the TTL output, with the 4 corner pins themselves taking in the VR sensor signal. The simplest solution for my ECU project would be to tap into those TTL signals, but I have no desire to go mucking around with the ABS computer. While the chances of causing it to malfunction are small, I don't want to chance it.

                            So, the way I plan to go is with some MAX9926 chips. I had this little board from a data logger I had installed in a spare Motronic, which has a MAX9926 on it. I soldered some new wires onto it and tapped into the ABS computer connector (shoved stripped wire ends into terminal slots).






                            The connector itself is very easy to work with, and popping the terminals out / replacing them with double-wires later will be nice and easy I think.




                            I got the oscilloscope on the two rear wheels' sensor signals, plus the output of the MAX9926, to verify that I would get a clean TTL signal, and that the introduction of the MAX9926 was not causing any sort of issue or change in the VR sensor signal that the ABS computer also relied on. Here is what it looks like in first gear at idle. Yellow is the right-rear wheel, and green is the left-rear which also had the MAX9926 tapped into it.




                            Here's ~10MPH...




                            And ~45MPH...




                            The other thing I was curious about was any voltage difference between the ECU ground (on the battery tray) and the ABS computer ground (up under the dash). The multimeter showed a negligible difference with RMS averaging.




                            The oscilloscope showed significant, but extremely brief, transient spikes. This is from the ignition, and the peak value was influenced by how I routed the wire from the ECU ground over to the ABS computer. So, at least some of this is driven by EMI in the long extension wire. Anyway, this is ~1-20MHz noise, which should be a non-issue with any reasonable amount of bypass capacitance installed in the VR conditioner circuit I'll make.




                            Other than that, I received the E36X today. It is a nice little unit with full conformal coating all over (looks like they dipped the 2 boards separately before assembling them, while being careful not to get it in the connectors). The large ignition coil driver ICs are placed intelligently near pin 55, which is the dedicated ignition ground connection. This thing is intended to run an M50, so any M20 folks here who want to go full COP could definitely use this thing. A big part of this thing's appeal is the fact that it'll drive the coils directly, negating the need for a "smart coil" conversion or any sort of external coil driver module.




                            Part of me was tempted to plan to void the warranty and solder wires between all of the "extra" connections and the unused pins on the Motronic connector, but I need to make a hole in the ECU case to run the MAP line anyway, so I think I'll just leave well enough alone. Although...I could run an external MAP sensor and connect its output to a spare analog input so that everything is routed through a single main loom...must resist the urge to immediately hack-up my new toy.






                            Other than that, I got out some of my spare Motronic bits and did a quick bench test to ensure that it was functioning and talking to my computer.




                            That's it for today. There will be plenty more TMI updates as I continue to work on this!

                            Comment


                              #15
                              I have no doubt you will be able to get the engine up and running pretty easily on the Link. The stock M42 does not idle that great so matching that will not be an issue either :) keep in mind there is a pretty big allowable error so you don’t have to be dead nuts for it to work right.

                              Calibrating fuel is pretty easy since you have a measurement to see how far off you are, and you can rely on closed loop trims to make small corrections.

                              For ignition timing there is margin of error too although its hard to get feedback without a dyno. A base map from a M50 will be good for starting until you get to a dyno. Unless the timing is super soft you wont have to worry about damage.

                              I noticed a pretty big improvement right off the bat with my install and I would say its still basically a base map for ignition and enrichments. Im sure your engine will respond well too.

                              If you want to run pencil coils, the CBR600 coils fit nicely under the vanity cover since they are “dumb” so they are smaller :)

                              I really need to put my car back together...

                              Have fun!
                              -Nick

                              M42 on VEMS

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