M42 ECU Conversion: Link G4X / E36X

[bmwman91]

So I actually ended up wiring in the two spare VR inputs I have to the front wheels (stole them from my currently useless ABS control module) today, seem to be working well.

For now I just have a single input for the rear, which is actually the speedo out signal, not ideal but good enough until I figure out a signal conversion setup for the two rear wheel VR sensors (or just suck it up and make a bracket)

Cool. Can you let me know how the signals look, as in does MS think that the wheel speeds are jumping around due to noise/ignition EMI, or is it fairly clean? A quick test is to idle at a stop and see if MS registers any wheel movement when parked. I did a bunch more poking around with the oscilloscope this afternoon and will need to put a bit more thought into conditioning the signals for the MAX9926 since ignition noise causes false triggers when the vehicle is not moving.

[JehTehsus]

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.

So I actually ended up wiring in the two spare VR inputs I have to the front wheels (stole them from my currently useless ABS control module) today, seem to be working well.

For now I just have a single input for the rear, which is actually the speedo out signal, not ideal but good enough until I figure out a signal conversion setup for the two rear wheel VR sensors (or just suck it up and make a bracket)

[wazzu70]

I had a really nice reply typed out and the forum erased it and wont let me retrieve it. Amazing how technology gets more clunky and error prone as time goes on! I should know to always make a copy of the text before trying to post :(

Ill try not to talk about diesels too much, but its somewhat relevant to control systems and strategy :) The modern common rail diesels are way more complex than the older stuff in order to increase fuel efficiency while meeting the current emission regulations. The modern direct injection diesels can employ a combination of pilot injections, pre injections, main injections, post injections, and late post injects depending on operating conditions to reduce noise, reduce PM, reduce NOx, keep the exhaust warm for catalyst efficiency, and increase fuel efficiency. To put the pulses in the correct place (in crank angle) and to inject the right quantity of fuel over the lifetime of the engine is very complex. Many of the injection pulses are very small quantities!

Example of injection pulse options per combustion cycle:



For detonation detection, its actually pretty simple. You just calculate a frequency based on the cylinder bore to get close to the detonation frequency, then you filter noise based on a window where you expect combustion to be occurring.

Knock Frequency = 900,000/(π×0.5 ×cylinder bore diameter)

The knock detection is really only there to save your bacon in the event you are getting some detonation, its not really a tuning aid. For tuning the best option is to make a set of “det cans” and use the human brain for signal processing. As Im sure you know making an algorithm to repeatedly and correctly perform a task that is basic for a human can be incredibly difficult to get the same accuracy!

Example cheapo det cans: http://www.vemssupport.com/forum/index.php?topic=1680.0

[bmwman91]

My car actually has not run in about 6yrs. Nothing to do with the standalone and everything to do with two kids and two working parents. Just starting to get time again for hobbies!

It was not very hard to get the idle and enrichments decent. For the most part enrichments were default values and the idle PID was the first one I ever tuned. I did notice a big increase in throttle response. I think getting rid of the AFM and all that helped as well as having a faster and more accurate processor and algorithms. The OBDI stuff is pretty crude compared to even basic stuff today! Like a lot of the tuning there is a pretty big margin for error where everything will still work well and be totally functional, just not completely dialed in. That last 10% is 90% of the effort!

I cant wait to get my car running again so I can optimize everything with what I know now. And yep, Im still doing calibration for heavy duty diesels so Ive learned some tricks!

Yeah, "life" certainly has other demands as we all get older. A lot of r3v has gone from 4 point harnesses to car seats!

Speaking of diesels, I picked up a Jetta TDI late last year (2006 with the BRM PD engine). They are interesting, and certainly different than gas engines in a variety of ways despite the mechanical similarities. Tuning on those sounds pretty interesting. From what I understand of the EDC16 ECU my Jetta uses, the injection programming is pretty sophisticated, what with small pre-injections followed by the main injection, injection timing, fuel heating & other stuff. The newer direct injection stuff may actually be simpler in some respects.

[wazzu70]

My car actually has not run in about 6yrs. Nothing to do with the standalone and everything to do with two kids and two working parents. Just starting to get time again for hobbies!

It was not very hard to get the idle and enrichments decent. For the most part enrichments were default values and the idle PID was the first one I ever tuned. I did notice a big increase in throttle response. I think getting rid of the AFM and all that helped as well as having a faster and more accurate processor and algorithms. The OBDI stuff is pretty crude compared to even basic stuff today! Like a lot of the tuning there is a pretty big margin for error where everything will still work well and be totally functional, just not completely dialed in. That last 10% is 90% of the effort!

I cant wait to get my car running again so I can optimize everything with what I know now. And yep, Im still doing calibration for heavy duty diesels so Ive learned some tricks!

[bmwman91]

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!

Good to know, thanks! HPAcademy on Youtube had an interesting video on AFR vs power where he did a bunch of dyno pulls back-to-back while varying the AFR, and it was surprising to me how little AFR matters (up to a point). There certainly is a lot of fudge factor to work with, although you have to watch EGT and knock as things go leaner. Still, it looks like finding an optimum AFR is not too onerous of a task. Ignition timing...yeah it seems like one needs to be a lot more careful with that as advance increases. Sssquid and I are going to try to work out some base maps using the tune he developed for Motronic, and I will plan to do the "real" tuning when I drive out there.

Would you say that you have gotten your idle and throttle-transition behavior to be better than stock with VEMS? I'd assume so since (IIRC) your career involves tuning for fleets of commercial vehicles.

[wazzu70]

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!

[bmwman91]

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!

[JehTehsus]

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.

[bmwman91]

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.

[JehTehsus]

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.

[bmwman91]

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.

[digger]

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

[bmwman91]

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.

[bmwman91]

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.