Hey guys, I’m getting ready to start a VVT swap on my ’91, and I have a complete ’01 donor car at my disposal. I’ve read the megathread and am going to follow the standard formula, nothing crazy. Just hoping to get some confirmation on my plans for building and installing the unassembled MS3 v3.0 kit.

As far as assembly, do I just follow the instructions in section 13 of the MS3base hardware guide, and then make the Miata-specific mods from DIY?

And then for the harness, I need the MS wire bundle from DIY and a male ECU side connector to plug into the factory harness (174917-7 from onlinecomponents.com), along with a db37 that comes with the kit, correct?

With that in mind, this is my complete shopping list for the ECU portion of the project:

MegaSquirt-III w/PCB V3.0 - UnAssembled Kit with black case
MegaSquirt Wiring Bundle - 23" Long
GM Open Element IAT Sensor with Pigtail
3/8" NPT Stainless Steel Weld-On Bung for IAT or CLT Sensor
JimStim v1.5 MegaSquirt Stimulator w/ Wheel Simulator -Unassembl
Wideband – probably MTX-L

Anything I’m missing? Any modkits or similar that are recommended for this setup? I'm open to suggestions - haven't really committed to anything since I haven't gotten the motor running in the donor car yet!

 

You're missing the ms3x.

 

Do I really need the MS3X to run the car properly? I'm not planning on forced induction for this build and none of the extra features seem necessary to run a nearly stock motor.

 

Depends on how much you hate yourself. Normally if you have to ask that question you are better off getting it.

Look at it this way, with the ms3x you solder 1 wire inside. 1 wire only. And it can do so much more. And you can run sequential spark and fuel
Flex fuel down the road. List goes on.

Or you can hate your life.

 

Hm, ok. Looked into it a bit more and I think I agree with you now. Adding me some X to the list.

 

I'll be following this thread as I am trying to do exactly the same thing.

 

You can run all those things and still hate your life.

 

Ok, so after some more research I'm fully in agreement with adding the MS3X, so I'll be going that route. Hopefully will be placing that order today or tomorrow. Current shopping list:

MegaSquirt-III w/PCB V3.0 - UnAssembled Kit with black case
MegaSquirt-III MS3X Expansion Card
DB37 solder cup connector for MS3X
MegaSquirt 3X Wiring Bundle - 23" long
MegaSquirt Wiring Bundle - 23" Long
GM Open Element IAT Sensor with Pigtail
3/8" NPT Stainless Steel Weld-On Bung for IAT or CLT Sensor
MegaSquirt Stimulator / DIYPNP Power Supply
MegaSquirt Stimulator v2.2 - UnAssembled Kit
Anti-Static ESD Protection Wrist Strap

For assembly, does the V3.0 board assembly guide for MS2 still apply to the V3.0 board with MS3? Seems like it to me, and this guide is more in depth than the one in the MS3 hardware guide...

In other news, I got the donor car running yesterday, and it purrs, even on two year old gas! Will commence removal of that engine today.

 

If you want the stimulator you also need the jimstimx. I would just skip the stimulator.

Also why stainless bung. Do you plan to have stainless intake pipiing?

 

I was thinking I could test just the mainboard for functionality with the standard stim like DIY recommends, whereas the 3X board should be functional out of the box, not having been assembled by an amateur solderer. If I can safely skip the testing portion, I'd be fine with that too.

Intake plans aren't 100% yet, but it's likely to end up with the sensor JB-Welded to either the stock intake or hopefully one of the sweet 3D printed ones.

 

Ok guys, pardon my ignorance, but once again I've done some more reading and pretty much answered my own questions (search, noob, right?). I've realized that by using the MS3X, most of the work will be done by that card, and as a result I'll be building much fewer circuits on the mainboard. Thus, the standard stim won't be able to do much and to get the ability to bench test operation of the ECU, I'll also need the stimX card to test those 3X circuits. Since I was really only interested in getting it so that I could check if I'd screwed up the assembly, I think I will skip the stim and do the manual tests with battery and voltmeter.

With that now in mind, I think I'll generally follow the WestfieldMX5 guide for 90-93 MS3X: 90 ? 97 MS3 | Frank's Westfield MX5 90 ? 97 MS3 | although I will look into it a little further to see if there's anything in particular to add or remove for my particular setup.

Just thinking out loud here, I'll post back after the holiday when I've got this thing in my hands. Cheers, guys.

 

Follow that guide but don't put the connector in the case it's annoying.

Main board is ridiculously simple with the 3x

 

Yep, that's what I'm realizing now, definitely the way to go like you said. And yes, doing a standard adapter harness, not the weird pnp-plug thing. Thanks for the input!

 

"weird pnp-plug thing" = DIYBOB?

 

I was talking about the part of the Westfield MX5 guide where he incorporates the OEM ECU plug into the ECU case, rather than using the db37 and building an adapter harness. 90 ? 97 MS3 | Frank's Westfield MX5 90 ? 97 MS3 | That part of the guide, I'm not following. I actually picked up the 64-pin plug and a breakout board for it from here: https://www.tindie.com/products/russ...ctor-bare-pcb/ So I'll be doing a diy-DIYBOB, essentially. I can build my own box for that.

 

Success! It works!! I got the 1.6 running on the MS today. It actually worked really well. I borrowed this guy's tune: https://www.miataturbo.net/megasquir...-signal-83789/ (thanks mkrazit!) changed settings to narrowband and batch injection, unplugged stock TPS, ran the MAP line, and it fired up on the first try! I didn't try to drive it w/o the wideband installed, but all the inputs seemed to be working properly, as far as I could tell. I'm super happy it worked out so well, I took my sweet time putting everything together.

That was the hard part of the project, tomorrow the 1.6 will be out!

 

This is usually frowned upon...



But hey at least "it's running" right?

 

Well, the extent of me using it was idling in my garage for 5 minutes. It was nice to know the ECU I built is actually functional before I add the huge unknown of a new engine. Just thought I'd share what I did should someone else have the same questions.

Thanks for everyone's help though!

 

A basemap could of provided the same results with less risk.

Glad you're making progress!

 

So, update time. VVT motor is in and hooked up. Haven't been able to get it to start however. I used DIY's MS3-pro 2001-2005 base map and adjusted all settings and I/Os to suit my application, to the best of my knowledge. While cranking, tunerstudio wasn't showing RPM or RPM sync. I changed cam input to MS3x camin, but how do you check the status of the crank signal? I can't find a reference to it anywhere in the software.

Unfortunately I wasn't able to record a log - after about 10 tries it decided to stop cranking, just a loud click from the engine bay. Changed batteries and no dice. Not sure what's up with that, called it quits for the night. Curious - will the engine crank without any ECU connected oncesoever?

I'll attach the tune file I'm currently working with; if anyone would like to take a look at it that would be great. Like I said above, the hardware ran the 1.6 without a hitch, and I followed the swap guide to the letter. Hopefully there's not an issue with my new wiring.