97 Miata MRE (turboz)

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MHM1
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97 Miata MRE (turboz)

Post by MHM1 »

Hello, I have this miata and it's been running on an MS3X I built for about 3 years now, but its finally starting to flake out on me and I have had it.
Last summer (6/20) I purchased an MRE off of eBay after researching the rusEFI project for about a year until that point. I'm a senior EE student and I like the idea of being able to modify and fix the code for the ECU if I so choose.

I'm a simple man, if it's stm32, I like.

Anyway, I finally got around to plugging it into my computer and playing around with it. I got the DfuSe driver installed and the firmware uploaded to the MRE using the rusefi_console tool I downloaded with the mre_f4_rusefi bundle.
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Probably something I'm doing wrong.
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AndreyB
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Re: 97 Miata MRE (turboz)

Post by AndreyB »

it sounds like you might have updated firmware without migrating settings via tuner studio.

as long as you do not have valuable settings I would suggest going into "popular vehicles" and simply reset to _current_ default MRE tune.

If you would like to save this tune please post it on www.rusefi.com/online

specific problem: on MRE we've made changes to TLE8888 driver and migrated from PE9 notation to "TLE.... something" for injectors and stuff and your tune still uses legacy PE9 setting
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mck1117
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Re: 97 Miata MRE (turboz)

Post by mck1117 »

MHM1 wrote:
Sun Dec 06, 2020 4:23 am
I'm a simple man, if it's stm32, I like.
Amen to that.
MHM1 wrote:
Sun Dec 06, 2020 4:23 am
Anyway, I finally got around to plugging it into my computer and playing around with it. I got the DfuSe driver installed and the firmware uploaded to the MRE using the rusefi_console tool I downloaded with the mre_f4_rusefi bundle.
Yes, like Andrey said, your best bet is to go in to TS and reset the board back to default settings, then unplug/replug and restart TS. That should clear it up.
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MHM1
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Re: 97 Miata MRE (turboz)

Post by MHM1 »

Ok so I finally am done with classes, and can start violently attacking this car once I am back home.
Here is a picture of it (to make Andrey happy).
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Those pictures were less than a month after I had painted it in the front yard. It has faded significantly from sun damage. I don't have the hardtop anymore, but the car is lowered a little at least. I'll take some more pictures soon.

I've spent some time going over what functionality I want out of the car long term and balancing that with what the MRE can support in terms of hardware.
Software wise, the only functionality I think I won't be able to program using the FSIO system is Flex fuel sensor and table switching/blending, but please correct me if I am wrong. I would also like to use speed density for cruising, and then MAF for idle, similar to how GM does it on some of their LS motors. It helps prevent IAT heatsoak, which is a problem I have had during the summers.

The only other function labels that might raise some eyebrows are ICPP and BOV. I have yet to actually build this system.
ICPP is an extra 3 bar map sensor that I will use to measure the pressure in the intake tube that goes after the intercooler, but before the throttle body.
BOV is a low side output that will drive a 12V solenoid "electronic blow off valve". Around this time I will also replace the stock miata throttle body with an ETB unit, and replace the no longer needed IAC low side output with the BOV output.

Here is the spreadsheet with the preliminary pinout I am thinking of using. Some of the OEM wiring side stuff hasn't been totally filled in yet, still working on it. I have attached the actual xlsx file as well.
miata wiring 12-09-2020.PNG
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For being "micro" this MRE thing is insane. It has the same number of IO as the MS3X for a third of the cost, and will support ETB, etc. Very cool.
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MHM1
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Re: 97 Miata MRE (turboz)

Post by MHM1 »

Forgot to attach the spreadsheet. Just in case you feel like editing.
miata wiring.xlsx
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mck1117
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Re: 97 Miata MRE (turboz)

Post by mck1117 »

MHM1 wrote:
Wed Dec 09, 2020 10:45 pm
Software wise, the only functionality I think I won't be able to program using the FSIO system is Flex fuel sensor and table switching/blending, but please correct me if I am wrong.
"real" flex fuel is coming eventually - we just haven't had anybody actually need it. If you can provide a pictured of a wired and installed flex sensor with your car sitting in front of a yellow handled gas pump, that would bump it up the priority list pretty quickly.
MHM1 wrote:
Wed Dec 09, 2020 10:45 pm
I would also like to use speed density for cruising, and then MAF for idle, similar to how GM does it on some of their LS motors. It helps prevent IAT heatsoak, which is a problem I have had during the summers.
You'll probably find that between charge temperature interpolation and closed loop fuel correction, you actually don't need to do this. With my IAT and CLT correction tables both set to NO CORRECTION across the board, the car idles at nearly stoich across the whole temperature range. It's that good.
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Re: 97 Miata MRE (turboz)

Post by AndreyB »

MHM1 wrote:
Wed Dec 09, 2020 10:45 pm
For being "micro" this MRE thing is insane. It has the same number of IO as the MS3X for a third of the cost, and will support ETB, etc. Very cool.
Please spend 8 minutes yelling about MRE on facebook or something?
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Re: 97 Miata MRE (turboz)

Post by AndreyB »

mck1117 wrote:
Wed Dec 09, 2020 11:25 pm
"real" flex fuel is coming eventually - we just haven't had anybody actually need it. If you can provide a pictured of a wired and installed flex sensor with your car sitting in front of a yellow handled gas pump, that would bump it up the priority list pretty quickly.
:lol: :lol: :lol: :lol: :D :D :D :D :D :roll: :roll: :roll: :roll: :roll:
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MHM1
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Re: 97 Miata MRE (turboz)

Post by MHM1 »

I have a flex sensor and plug. It of course still needs to be wired into the car.

I am currently working on getting the car running back on the OEM ECU and MAF setup to troubleshoot any other non ECU related issues I have been having, namely the starter. I have completely overhauled the battery and grounding wiring in the rear of the car. I switched from the fragile miata AGM to a large heavy lead acid battery I had from my old 300SDL Benz (rip). Next is the front grounding strap. I am using 2 gauge wire everywhere and sealing the crimped lug ends with raychem+liquid electrical tape. This car lives outside.
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I also removed the AC because there was a leak in the system and it was inop. This car will no longer be a daily driver anyway, but i'm keeping the important parts just in case.
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P.S. This is the belt you need if you run miata AC with no PS. A couple washers on the bottom of the ac bracket provide tension.

After the battery, I redid the engine bay injection and ignition harnesses, since some of it was damaged. I also converted the ignition harness to be able to switch between LS coil sequential and OEM wasted spark coils with just a swap between two subharnesses I built using aftermarket LS ignition coil harnesses.

Since it has been raining for the past two days I started messing around with configuring the MRE. I have made the decision to switch to canbus for the wideband data, since I have an AEM X-series. I did run into a snag however with the vehicle speed sensor input conflicting with the miata CAS inputs. It looks like I can only use pin 25 and 45 for VSS, but is it correct that both of these are used for the CAS signals?
miata NA.PNG
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Is this correct? And if so, do I have any other non-canbus options for getting VSS? My 97 has a VSS output from the instrument cluster.
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Re: 97 Miata MRE (turboz)

Post by AndreyB »

We believe that there must be a way to use VSS on miata MRE but no one has documented HW and FW mods for that as of today. Maybe one day soon.

https://github.com/rusefi/rusefi/issues/2083
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MHM1
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Re: 97 Miata MRE (turboz)

Post by MHM1 »

It looks like this thread shows the waveform for an NB sensor.
https://www.miataturbo.net/ecus-tuning-54/nb-vss-vehicle-speed-sensor-details-73810/

I will get some oscilloscope data for the NA instrument cluster output when I get the car running to see if it is similar or if it is already an ideal square wave.
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Re: 97 Miata MRE (turboz)

Post by stefanst »

90% sure it's a 5V squarewave.
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Re: 97 Miata MRE (turboz)

Post by fan »

I think the raw signal output is a sine wave, but I don't have a 97' so NVM :)
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Re: 97 Miata MRE (turboz)

Post by Gepro »

I think the MRE is limited by the INI file.

I tune my INI file in order to add AV2 as trigger input, and it looks to work fine.

I am sure it is possible to use any AV input for 5V VSS input.

If your VSS signal is VR signal (sine wave) you need an external VR conditioner before MRE.
mck1117
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Re: 97 Miata MRE (turboz)

Post by mck1117 »

Gepro wrote:
Sat Dec 26, 2020 11:03 pm
I am sure it is possible to use any AV input for 5V VSS input.
That's not quite true. Right now it only works on particular pins (one of which you managed to find on accident), and there is a limitation on frequency that you can input to those pins before it gets filtered out.
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Re: 97 Miata MRE (turboz)

Post by Gepro »

Thanks for the information !! I didn't think about it, looks like there is a 160Hz input filter :roll:
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MHM1
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Re: 97 Miata MRE (turboz)

Post by MHM1 »

So update. I got the miata running on the stock ECU after a good 3 weeks of working in the cold. I chased my tail alot with vacuum leaks trying to get it to run on the MAF. Seems silly, but I wanted it running on a baseline to make sure I had no chassis or engine bay wiring issues before I started converting to MRE. The car was running poorly on the MS3X before it sat and I wanted to verify that it wasn't because of some non-ecu related issue.

I'm now going to wait to install the MRE until classes begin again in a couple weeks because I have some other stuff to do over the break. In the meantime I am collecting all the parts to convert the miata to ETB. I have acquired an E46 ETB for $26 on ebay and designed up an adapter flange I will print out of nylon. (High end 3D printing is my other hobby).
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97 miata throttle body flange.PNG
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miata ETB.zip
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I do not yet have the E46 throttle body in hand to verify the bolt pattern of it, but the miata TB dimensions I know are good. I have verified them with a real 97 throttle body.
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