Megasquirt 3 on M20B28 stroker, using M50TU harness

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Megasquirt 3 on M20B28 stroker, using M50TU harness

Postby hassmaschine » Tue Sep 07, 2010 6:24 pm

The basics:
M20B28
Megasquirt 3 CPU, MS3x I/O board
M50TU harness, 88pin connector
Full Sequential fuel + Spark
99% plug and play

Basically, it's like doing an M50 swap (as far as wiring), only I'm not using an M50, and I'm not using the M50 computer, just the connector.

After thinking about it for a while, and knowing how limited my free time to work on it will be, it didn't make sense to try and add all those pins and wires to the stock Motronic 1.3 55 pin connector. I already added 2 pins for wasted spark outputs, and it was a total nightmare.

So I spent some time looking through the E36 ETM (http://www.wedophones.com/BMWManualsLead.htm) for 93-95 325i's (Motronic 3.3.1), and decided it made far more sense to use an M50TU harness. It has everything I need (and more that I don't), plus my harness is getting a bit old and crusty anyway.

After a week of research, I came up with this chart:
http://www.megasquirt.325ix.com/MS_to_Motronic/MS3%20to%20Motronic%203.3.1.html

I've decided it doesn't make sense to buy M50 coils, and build a driver circuit (6x BIP373 mod kits from DIYautotune). In the end, LSx coils make far more sense, and since they have built in drivers I don't hav to send high current signals through the harness (noise elimination!).
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The best part about using generic GM stuff? You can buy high-quality off the shelf plug wires for $50 (+S&H).
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hassmaschine
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Project Log

Postby hassmaschine » Tue Sep 07, 2010 6:24 pm

August 29 - started research into MS3 PnP using M50 harness. After a couple days reading the ETM, figuring out all the pins, then researching the C101 to X20, and a few other misc items, I had a pretty good map for the entire thing worked out. I'm 99% sure it will just plug in and run. The plan is to use a fully assembled MS3/MS3x with a V3.57 motherboard. I won't have time to build a V3.0 board or I would (proto area). Need to figure out a mount for my accelerometer, as well as a better location for the econometer board from Seattlecircuit.com.

September 6 - bought a set of Gen III LS1/LS2 etc. coil packs on ebay, $140 shipped. I want the brackets so I can figure out how to mount them to the valve cover before I have it powdercoated (still deciding if I want it done with the intake manifold, or just have the manifold blasted and do the cover later). Wiring the LSX coils to the M50 harness should be a snap. Need to call Jegs or Summit and get some wires/plugs for a custom set of "CNP" (Coil Near Plug) wires.

September 7 - Taylor makes a universal wire set with 6 wires, straight plug boots, and male+female coil ends. it's $60, which isn't bad, and the quality should be top notch:
http://www.summitracing.com/parts/TAY-83245/

Sadly, the V8 set is the same price:
http://www.summitracing.com/parts/TAY-73255/

Summit sells a similar product for $40:
http://www.summitracing.com/parts/SUM-G826R/

Edit: there appear to be several pre-made LSX wire sets that are around $50.

Jegs has a LS1 coil wire kit for about $40, all built:
http://www.jegs.com/i/JEGS/555/40216/10 ... tId=758101

There's a Taylor kit for ~$52 from summit:
http://www.summitracing.com/parts/TAY-84244/

a few on ebay under $40 but I don't know if I trust them.. random, no-name parts.

September 8:
Bought the Taylor wire kit
http://www.summitracing.com/parts/TAY-84244/
~$60 shipped. Consider that stock BMW wires run $100-200. What do 6 new BMW coils cost? I don't even want to know.

September 9:
Missed out on a deal for an MS3, MS3x, and V3 board all assembled for $450. Damn. Oh well, I don't need it right away anyway.

Getting an E34 M50TU harness. It's a little shorter than the E36 harness but you can hide the relays in the glove box. Plus it is cheap and unmolested, and I guess it has the oil level sensor wiring built in like the E30.

September 10:
Paid for the E34 M50 harness, found a 318is ECU as a core for $25. Need the brackets to mount it, wiring covers, maybe a wire kit from DIY (or hack up the harness from my parts car), C101 connector and pins, and an MS3 case, then I can start building the harness.

Taylor wires should be here today, LS1 coils on Monday. When I get my valve cover back from powdercoating, I'll start working on mounting the LS1 brackets.

EDIT: Ordered the MS3, V3.0 unassembled, MS3x, an extra IAT/connector, some wires, and the DIYautotune efI book. I've decided I may as well just go for it, I can sell my entire MS2 setup with the harness and all to pay for it.

Also the Taylor wires came, they're perfect for my use. I'm super excited to get the LS1 coils mounted on the new valve cover, it's going to look so awesome!

September 13:
Ordered pins/connectors for the DB37 on the MS3x. Already have everything for the MS3 DB37, but I'm going to build and sell an adapter using the core 88 pin ECU, and connect the DB37's directly to the E35 M50 harness.

Parts/links:
https://www.mouser.com/Search/ProductDetail.aspx?R=205209-7virtualkey57100000virtualkey571-205209-7

https://www.mouser.com/Search/ProductDetail.aspx?R=66569-3virtualkey57100000virtualkey571-665693

https://www.mouser.com/Search/ProductDetail.aspx?R=205210-8virtualkey57100000virtualkey571-205210-8

https://www.mouser.com/Search/ProductDetail.aspx?R=66570-3virtualkey57100000virtualkey571-665703

these make it far more convenient to solder the individual wires. Just solder on the pins, shrink wrap, and plug them in when you're done.

Parts list has been updated too.
http://www.megasquirt.325ix.com/MS_to_Motronic/parts%20list.html

I also made an order through Blunt Tech for the 318is wire harness covers and the C101 connector/pins. I'm thinking I have everything I need to start the build, now I just need some time. :)
hassmaschine
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Re: Megasquirt 3 on M20B28 stroker, using M50TU harness

Postby hassmaschine » Thu Sep 16, 2010 4:55 pm

September 14:
shitty cell phone pic of the coils:

Image

they're actually from an LS2

the cylinder spacing is a bit off (~105mm or so) so I'll need something else to mount them to the valve cover, or just deal with it being off a bit.

September 15:
MS3 arrived, I wasn't home to sign for it so I'll have to pick it up from the post office. Damn.

September 16:
I updated adapter chart, figured out the start circuit Goathumper came up with:
http://www.megasquirt.325ix.com/MS_to_Motronic/Start_Circuit.html

The original Goathumer thread:
http://www.e30tech.com/forum/showthread.php?t=50206

I'm going to go with this instead of the relay mod. The relay mod works fine but it increases the current through the ignition switch. I might mod my old MS2 PnP setup to use the start circuit as well before I sell it, or give them the parts and let them do it..

I made another mouser order for the 2n2222a, diode, and resistors. I hate it when I figure something else out I needed a few days after ordering, I just end up paying double shipping..
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MS3 assembly

Postby hassmaschine » Sun Sep 19, 2010 12:51 am

September 18:
Built the MS3 today..

the kit:
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MS3 CPU:
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MS3 expander:
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resistors installed:
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Diodes:
Image

Capacitors:
Image

UC's:
Image

Jumpers:
Image

testing power circuits:
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Plug in the MS3 CPU, install firmware, test comms:
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Plug in MS3x:
Image
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it works!
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USB, on board SD card.. yum
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Default screen:
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I was able to load my MS2/e 3.0.3u MSQ, which is nice since most of the settings are the same, I don't have to redo my VE map, ignition, warmup curves, idle, etc. etc. etc. Basically I need to reconfigure for sequential spark, injection, and plug it in. still waiting for the M50 harness though..

the nice thing is since the MS3/MS3x basically does everything, I don't have to do any of the normal V3.0 mods. Just do a base V3.0 build and plug everything in, configure jumpers and I'm done. Of course I have some other mods (accelerometer, MPG gauge, etc) that I need to do but they aren't critical. :)

still have all those I/Os on the motherboard open too. I think I'm using 1 output and 1 input right now. lol
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