M42 ECU Conversion: Link G4X / E36X

[Dj Buttchug]

Much of the work you are doing I have already done on my engine. MAP sensor external FPR ect. This could make the job a lot easier for me. If all that was needed for me was to re-pin some wires on the Motronic I would probably pull the trigger. I wonder to if you could load the E36 base map and modify it to run. I dont know enough about this. I have been getting pretty good with using the Link system and tuning. Still learning everyday!


Edit: After some further research I found this to be interesting. For others interested in doing this with a more plug and play type application this could be a way to go. It would alleviate the need for all the tedious work OP is doing (not to downplay in any way as this is quite impressive) but would make us guys that hate wiring (me) more inclined to take on the task. Price for this harness plug in as well as whichever ECU you decide could sway a decision. Time saved could make it worth it.

PNPECU Link adapter M42 E30

[bmwman91]

Email is great - I have a printer, just a matter of removing all the junk I'm "storing" on top of it

Here ya go. STEP and STL files.

http://www.e30tuner.com/assist/E36X_Board_Puller.zip

Bumping this thread because I so badly want to switch my 318is from MSV1 to Link. Running E36G4X on my E34 has been a complete dream. In for more progress on this!!! Looks great already!

So for the most part, the E36X can be almost plug-n-play for the M42. You would need to re-pin some stuff in the Motornic plug, but it is really easy to do once you know how to separate the terminal carrier pieces in the connector housing, and the terminal extraction tools are like $20 on Amazon. The only tricky bit would be the addition of a MAP sensor since there is no immediately obvious good place to install one. You could probably hack something together with the vacuum line for the FPR, or maybe drill into the TB heater plate and use the existing hose barbs if it is not connected to the coolant system anymore. Modifying the intake manifold like I did is a good way, but not everyone has access to a machine shop. I might be down to mod M42 manifolds for people for a fee, though.

The other item is the IAT thermistor. You could leave the AFM in place and just use the one in there, but that sort of sucks as a solution. If you mod the manifold you can just use the Bosch T-MAP which has both sensors in one. If going the TB heater route, then I think that you might be able to stuff a generic GM IAT sensor into the unused port in the intake bellows which is on the bottom and like 2" in front of the TB.

So a little repinning and IAT + MAP sensors aside, the E36X can run the M42 just fine without any other changes. It has the high current ignition drivers and VR sensor conditioners built-in which is awesome. There are not too many aftermarket ECUs with the ignition drivers inside. My original plan was to swap to some VW coils with internal igniters, but in the end the M54 coils that I have in the COP setup are fine and a little simpler in terms of wiring (ignoring all the work I put into the shielded wires for them lol).



As of now, I am basically ready to swap the ECU and harness into the car. The PST-F1 for the oil system needs to be screwed into the back of the head, and the knock sensors need to be installed (still gotta remove the oil pressure switch in the filter housing to make room for the front one). For the moment I am in a holding pattern since I am working on getting the final arrangements for the full repaint settled. It looks like I may have FINALLY found a body shop that will take on the repaint project, and at a price that I can still justify to myself. So, that will probably be a couple of months until it is all sorted out and done. Thereafter I will pick this back up again since the next phase is to start tuning. I want to find a local tuner to work with on a dyno...I know that I can get the car to run, possibly reasonably well, but my years working with Sssquid on tuning the stock ECU made it clear that a professional can do a better job and faster. I'd love to trailer the car out to Sssquid and do it there, but it might be hard to find the time (and vacation hours) this year lol. We'll see.

[Dj Buttchug]

Bumping this thread because I so badly want to switch my 318is from MSV1 to Link. Running E36G4X on my E34 has been a complete dream. In for more progress on this!!! Looks great already!

[Northern]

Email is great - I have a printer, just a matter of removing all the junk I'm "storing" on top of it

[bmwman91]

Good progress, I might hit you up for that board removal tool someday lol.

Ha, yeah I am happy to share. I can either mail it or send you the CAD file if you have access to a 3D printer.

[Northern]

Good progress, I might hit you up for that board removal tool someday lol.

[bmwman91]

beyond mind blowing level of intricate work. well done

Thanks dude, it's been quite the journey! Doing this has been something I have wanted to do for like 17 years, and I finally have the time, skills, and money to do it properly. At one point back in college I attempted a Megasquirt conversion, and I lacked the 3 aforementioned things. I will always remember the MegaManual instructions' top pieces of advice...do not let it be your first soldering project, and do not try to build a harness using all black wires to save money. Naturally, I did exactly those two things lol. Let's just say that the car remained operating on the stock ECU!



More progress this week. I got my PCBs and assembled the EGTCAN unit. After that I got to work on the code for the microcontroller (Teensy 3.2). It is super simple since there already exist fully functional SPI and CAN libraries for it, so the whole thing, fully functional with comments and an extra serial logger, is under 200 lines of code. Sometimes I wonder why I spent so many years writing assembly code lol...then again, there is a lot more out there for hobbyists now than there was 10-15 years ago.

Test and debug action. I needed less than an hour to troubleshoot some issues with the data being sent over CAN. One...not twisting the wires on the little test harness actually caused some bits to get flipped here and there, probably due to EMI from other stuff on the bench. Two...some data type conversions in the Teensy code were doing unexpected things so silly values were being sent to the E36X. Once I corrected that stuff, all was well.




Here is the assembled board. it is really a very simple circuit. Few signal connections, and lots of extra space. The real work was in trying to lay it out for good isolation between analog and digital sections and getting good thermal links between the MAX31856's and the TC terminal blocks. There are 4 power supply rails in the thing: ~12V Vbatt input, 6.3V intermediate rail from an LT3080, and two 3.3V rails (analog and digital) regulated off of the 6.3V one. I could have just run Vbatt to the 3.3V regulators, but thermals were a concern since they were really really small. I selected the ones that I did because they had really good input noise rejection and seemed to only be available in a small package. So, having them regulate down from 6.3V instead of 12-14V put a lot less thermal load on them. The Teensy is the most power hungry item there, and it has its own 3.3V regulator, so I ran the 6.3V rail to it. That way, only the MAX31856's and CAN transceiver chips use the two 3.3V rails I put in there. Stacking the LDO's like that should, I hope, give extra immunity from alternator and ignition noise present in Vbatt. Also, I have a bunch of the LT3080's left over from past projects, so it did not really cost me any extra to use one here.






And here is a screenshot of everything agreeing. The E36X will only take integer values for CAN thermocouple inputs, which is perfectly fine since EGT is going to be several hundred degrees Celsius. The reported values in PCLink agreed with the values being sent back to the Arduino IDE over serial, so it is all good. There is some additional work I want to do to calibrate the circuit and thermocouples, although these should easily be within 5-10°C of the true temperature. But, where's the fun in "good enough"?!

The LT3080 definitely generates a little bit of heat, and it is really cool to be able to see the thermal gradient across the four MAX31856's when reading their cold junction temperatures. The warmest one is nearest the LT3080, and they each get a little cooler as you look at ones further and further away. You can see this in the 2nd - 5th numbers in each row in the screenshot (first one is time in seconds, last four are the EGT probes).

[OSAH racing]

beyond mind blowing level of intricate work. well done

[bmwman91]

Not sure where you got that adapter,but I have been using the brass Autometer metric to ASE adapter forever (12 and 14 to 1/8npt) Never had one fail.

Amazing what you can make at home with just a little ingenuity. Good on ya!

I got the adapter from a company in NZ that sells various fittings, as well as the Bosch PST-F1 sensor for (at the time) a much lower price than US sources. I am always glad to have access to lathe!


There has been a little work ongoing with this over the last month or so. I decided that I want to add a CAN connection to the system for future expansion and whatnot. The immediate need will be for a 4 channel EGT converter since I already have the probes, and they will aid in tuning. Since I changed jobs, I no longer have the ability to borrow expensive DAQ hardware on weekends, so I will need my own thermocouple converter. There are commercially available products out there, but a) they are IMO overpriced for what you are getting, b) proper analog design for interfacing with thermocouples and dealing with cold-junction offset is not trivial and I learned a lot about how to do it at the last job, and c) DIY is what this is all about!

So I designed my own CAN-EGT box. The PCB design is done and I need to send it out for fab. The TC signal conversion will be done by a set of MAX31856 chips. These are about as good as one can get with off-the-shelf products, and they save me a ton of time. The board is 4 layers, with a lot of solid copper all throughout, but especially under the TC input terminals since the MAX chips are directly beneath them to ensure as much cold-junction accuracy as possible. The MAX chips are not cheap (~$11 each), but I already had 4 of them from another project. Between the remaining BOM items and the PCBs, I am looking at under $100 for the materials. The daughterboard in there is a Teensy 3.2, which I also already had laying around. If I was actually going for minimum size and layout efficiency, I probably would have used a dsPIC and programmed it in ASM or C, but the Teensy is just a heck of a lot faster since it uses the Arduino IDE and has a ton of existing libraries already. This is a one-off after all.










Inside the ECU, I replaced the various internal jumpers with new wires that match the colors of their exterior counterparts, and just look nicer since Tefzel insulation deals with the soldering heat a lot better. For the outside, I will need to un-tape a few inches of the main loom where it exits the main connector housing so that I can add the CAN pigtail.






The other thing I did was to 3D print a board removal tool. Since I am not using the built-in 7BAR MAP sensor, I wanted the rubber hose out of my way for routing the new jumper wires. The way that the boards are assembled means that a lot of pulling force is needed across the side with the B2B connectors. Without a tool like this, a lot of bending would occur on the board, which is bad for solder joints and copper traces. Yay, 3D printing.

[ForcedFirebird]

Not sure where you got that adapter,but I have been using the brass Autometer metric to ASE adapter forever (12 and 14 to 1/8npt) Never had one fail.

Amazing what you can make at home with just a little ingenuity. Good on ya!

[varg]

Very well documented, I like seeing these no-detail-spared conversions come up from time to time. You probably couldn't ask for a better starting platform to learn tuning than a low-strung NA job like your M42. I know it's not stock, but short of a money shift it's not easy to hurt it either, even with a shoddy tune.

[bmwman91]

Dang dude, looking good! You put my harness skills to shame for sure :)

I like what you did with the IAT/MAP sensor. I really dislike the hard line I have for the MAP sensor. A combined sensor like that would work great! I also liked how you milled the flat spot and used inserts for proper sealing!

Ha, thanks! Considering how long I have been sitting on this project and allowing my OCD to run wild on the planning+implementation, it had better all work out! Designing and building the physical parts is the fun and (probably) easy part...tuning is completely foreign to me, so it is going to be a heck of a learning curve. I'd like to get the car to idle and be drivable on my own, but for the actual final tune (performance, drivability / running quality) I will be looking for a professional tuner to work with.

Once the car is running at peak performance, I will look into an ITB conversion lol. You know, you can't just let a car run well and drive it...gotta always be breaking stuff!

[wazzu70]

Dang dude, looking good! You put my harness skills to shame for sure :)

I like what you did with the IAT/MAP sensor. I really dislike the hard line I have for the MAP sensor. A combined sensor like that would work great! I also liked how you milled the flat spot and used inserts for proper sealing!

[bmwman91]

All fab work is done (as far as I can tell...fingers crossed that I don't find any more lol).

Famous last words!

I went to assemble the PST-F1 into the aluminum adapter that I bought, and it did that thing where the wrench keeps turning, but it is not getting tighter. The Bosch datasheet spec's the torque at 40Nm (~30 ft-lb) which is sort of a lot for an M10, but I don't need leaks. The sensor in the previous post torqued down just fine in the stainless fuel line adapter, so I am assuming that the aluminum used in this adapter is some low-grade junk. On top of that, the adapter is really not well designed. The company that makes and sells them says that they are specifically for this sensor, which is primarily intended to seal using the conical surface at the tip of the threaded barrel. Well, you can see what happened. The force from the conical part caused the adapter to start shearing. I am REALLY glad that this failed on the bench when I was applying the specified torque. If I had gotten it to seat, installation into the head would have put even more shear load on the same thin cross section, and I probably would have had a broken adapter stuck in the back of the head.






Just for fun, I cut it in half with a hack saw and sanded it smooth. Yeah...not a great design, and certainly not rated for the application it says it is for. You can see where the sensor started pushing in the aluminum by the step in the inner 45° surface at the bottom of the M10 hole. The initial minimum section thickness through there is ~1.9mm.




Anyway, I made a new one out of some 303 stainless. The same cross section is now ~2.75mm thick, and I am using a copper crush washer so that the sensor is not pre-loading the weakest part of the adapter. I think that this should take care of any issues.






The sensor torqued down just fine, and I used a little blue thread locker for good measure.

[bmwman91]

Phew, big milestone. All fab work is done (as far as I can tell...fingers crossed that I don't find any more lol).

I had a local guy TIG the fuel tee together and it came out looking very good. I have it a quick whack with a fine wire wheel to get it all to a uniform color and installed it. The sensor is installed with 40Nm (30ft-lb) per the datasheet. While I was in there I replaced all of the fuel soft-lines under the hood, and I am going to do the ones at the rear of the car in the near future. other than that, I just need to install the sensor for the oil into the back of the head. For now I am going to put things back together and keep running on stock engine management, probably until closer to Christmas when I will have more of a chunk of time to dedicate to bring-up with the new system.

For now though, here's how the fuel stuff turned out. It almost looks OEM!