I was just reading the thread on the 3d printed car parts, and had this thought a bit, but could one convert an OBD1 to 2? That would open up options to monitor the car more and I see these different track assistants that have OBD2 ports that allow for logging your throttle/brake etc.
Specifically, I have a 91 MR2 - is it possible? There wasnt a 96+ here in America to buy and swap parts from, so I wasnt sure if this was a possibility for not too much money
That would be a significant headache. Since your car no longer needs to pass emissions, wouldn't it be easier to run an MS or other standalone that has all the logging abilities you could ever want?
Or, is it even possible to datalog the '91 ecu? Lots of OBD1 cars have ECUs that can still output all those parameters, its just not the OBD2 standard... more wild west.
I would say no. What most here would be looking for are the simple comprehensive component monitors- just to detect what was broken. But finding a powertrain that was close enough that the system would work is not really that easy.
For the specific emissions monitors- there's pretty much no way to carry those down, as they are very specific to the hardware that was installed on the vehicle it came with.
But for what you want, you need to find the entire powertrain to swap back to your MR2, and include all of the hardware- catalyst, evap system, etc.
Depends? On my VW Corrado it's not that hard to do, I grab the OBD2 engine wiring harness, ECU, ECU to fuse box harness, MAF, rear O2 sensor, throttle body and intake manifold from an OBD2 VR6 car and away I go. Some work is involved in the wiring harness from the OBD2 ECU to my OBD1 fusebox but many people have done it.
On your MR2, was that car ever available OBD2? If so, you'd need all the necessary parts and than the pain to install it all.
The last US model year for the SW20 was 1995, which probably means Toyota didn't want to spend the money to OBD2-ize it.
Even if there was a 1996 car to steal parts from, it would still be a huge undertaking. Looking at cars that did go across that model year gap (a Miata, say), you'd probably be changing the ECU, entire wiring harness, and likely adding some sensors that weren't present on the OBD1 car.
As for the track assistants, not all "OBD2" is the same in that regard and I tend to suspect that it wouldn't do what you want anyway. The standard/basic data rate for OBD2 is very slow, something like 4 data values per second, for all types of data combined. That means that if you wanted to log TPS and RPM, you'd get each of those twice a second. That data rate can help when diagnosing things like bad O2 sensors, but as far as track assistants go it's pretty much useless. Things like the Garmin Catalyst are really intended to be used on cars about 10 years newer than that, where the data rates are much higher. They also often use CAN bus, which isn't technically part of OBD2 but is sometimes present using extra pins on the OBD2 connector.
If there is an OBD2 version of your engine out there, preferably one that's mechanically identical, you could swap over all the electronics from the later car - the ECU and its wiring harness, and any sensors that are different.
If your engine never had an OBD2 version, it's a lot harder - very few OBD2 ECUs (and definitely no Toyota OBD2 ECUs that I'm aware of) are hacked to the point that they can run an entirely different engine.
On the other hand, if your track assistant can log CANbus from race ECUs, there's several companies that make putting a race ECU on an MR2 Turbo a plug and play deal. Just saying. 
Basic OBD2 data logging is not something worth doing a lot of work for, the update frequency is usually terrible, especially on pre-CANbus-era OBD2 systems. +1 for a race ECU if you want data logging capabilities.
codrus (Forum Supporter) said:Even if there was a 1996 car to steal parts from, it would still be a huge undertaking. Looking at cars that did go across that model year gap (a Miata, say), you'd probably be changing the ECU, entire wiring harness, and likely adding some sensors that weren't present on the OBD1 car.
That's not what I would call a huge undertaking, but it obviously depends on the car. I recall swapping the entire powertrain harness + a few sensors in our Lemons Saturn in less than an hour. My memory is a bit fuzzy on that one, but I think there is only a single extra temp sensor in the '96 harness. And that might be wrong, that may have started in '95 like the EGR and vac hose changes.
In the most basic sense? Yes, it's possible but figuring out why you want obd2 specifically would dictate what path you took. All the emissions and monitoring stuff? I can't imagine grafting most the ecu and sensors from a later obd2 manual corolla would be crazy hard. It wouldn't function perfectly but would get you in the ballpark. If you're just after the performance side of sequential injection, coil on plug, fancy data over a single port then a standalone would probably be much more straight forward. MS, speeduino, even haltech or something like that. Unless someone has already taken a later corolla/camry ecu and striped off all the emission/security features?
So flip the question- what do you want to monitor? And how do you want to monitor it?
You can build a data acquisition system that will output data to whatever you are using- many microcontrollers out there have A-D capability.
iansane said:In the most basic sense? Yes, it's possible but figuring out why you want obd2 specifically would dictate what path you took. All the emissions and monitoring stuff? I can't imagine grafting most the ecu and sensors from a later obd2 manual corolla would be crazy hard. It wouldn't function perfectly but would get you in the ballpark. If you're just after the performance side of sequential injection, coil on plug, fancy data over a single port then a standalone would probably be much more straight forward. MS, speeduino, even haltech or something like that. Unless someone has already taken a later corolla/camry ecu and striped off all the emission/security features?
If this is a naturally aspirated MR2 with a 5S-FE, an ODB2 Camry or Celica ECU with the same engine might work - but tuning one of those to handle boost with a 3S-GTE would really have your work cut out for you.
Pretty sure that you could create sensor locations for the OBD2 but it might be frustrating and complicated.
I went the other way - I was swapping an OBD2 engine into an old British sports car and being in Canada I wanted to avoid several rounds of mailing the ECM off for reprogramming (about the only option back when I did this in 2007), so I picked up an OBD1 ECM from a similar engine (1989 instead of the 1995 original for my engine) and backdated, so I could mail chips around instead.
You need a good programmer but that can work pretty well.
In reply to codrus (Forum Supporter) :
Garmin Catalysts are totally stand alone, they have and use no OBD2 or CAN-BUS information from the car. That's basically the only thing I don't like about it, it'd be nice if it could pick up an RPM signal from the car to overlay on the data.
docwyte said:In reply to codrus (Forum Supporter) :
Garmin Catalysts are totally stand alone, they have and use no OBD2 or CAN-BUS information from the car. That's basically the only thing I don't like about it, it'd be nice if it could pick up an RPM signal from the car to overlay on the data.
If you are using a logging system that specifically uses the CAN bus on a car- that's published info. So, in theory, you can make a data acq system that can convert the data input into a signal that can be transmitted over CAN so that the lap logger can deal with them.
I know arduino has CAN on it, and typically enough A-D to input the signals you want.
alfadriver said:docwyte said:In reply to codrus (Forum Supporter) :
Garmin Catalysts are totally stand alone, they have and use no OBD2 or CAN-BUS information from the car. That's basically the only thing I don't like about it, it'd be nice if it could pick up an RPM signal from the car to overlay on the data.
If you are using a logging system that specifically uses the CAN bus on a car- that's published info. So, in theory, you can make a data acq system that can convert the data input into a signal that can be transmitted over CAN so that the lap logger can deal with them.
I know arduino has CAN on it, and typically enough A-D to input the signals you want.
It's not quite "built in", but but a CAN bus shield is inexpensive and it's only a few lines of C to poll a sensor and generate a CAN bus value to the address you need.
And yeah, I mean "Solo 2 DL" or something like that instead of "Catalyst" above.
As for wiring harness swaps, it depends a lot on the car. On a Miata there isn't a separate engine harness so you're pulling out the dash. I'm not sure how bad an MR2 is.
CAN data goes through the data link connector, I believe this is what "OBD-II" data outputs use. I have seen what a VIRB can read from the DLC and it's definitely better than the 1 hz with delay or whatever absurdly slow generic data output is.
I had half a mind to give the cheapest GM ECM I could find its own RPM, TPS, and MAP signals just to send data out to my camera.
I think it'd be neat to see throttle and brake inputs (percentages/graph throughout a lap etc), not caring about emissions stuff, honestly.
Thanks for the replies folks
My '91 MR2 Turbo was OBDII. After I swapped in the Caldina 3SGTE. Although it was Japanese only & US code readers said "I don't speak Japanese".
I added a obdII port by the ecu, added a lm347 dongle & used Torque Pro & a Japanese translation addition. Never had any codes. Was amazing that the boost was only 7-8psi stock & it was very impressive. With Torque Pro I could display anything the ecu was doing on a fire tablet.
So uh, I guess they're just getting into datalogging this computer now? As in now, now: https://www.mr2oc.co.uk/forum/95/168964.html
What do you think of the link so far? I don't know if it works with a '91 though. This is 92-93.
hybridmomentspass said:I think it'd be neat to see throttle and brake inputs (percentages/graph throughout a lap etc), not caring about emissions stuff, honestly.
Retrofitting OBDII for those kind of features is like using a 100lb sledge to hang a picture nail (the brake stuff notwithstanding which isn't typically tracked by older OBDII setups anyway).
A standalone setup with some additional sensors would be way, way easier. I think there is even a MSPNP setup available off the shelf for the 3S engines.
There are a couple of examples of translating OBD1 to OBD2. It would be cool to use an Arduino to make a generic OBD1 to OBD2 translator but you would still need to import an adx/aldl file for your specific vehicle to make it work. Then you could have OBD2 BT output.
https://github.com/mr-sneezy/ArduinoHondaOBD1_to_OBD2_BT
ALDLdroid is a nice app for monitoring and logging OBD1 data. It uses an adx/aldl file for your specific vehicle to do the proper translation of data.
https://www.aldldroid.com/
Aside from all the good reasons not to do it listed above, yes it's totally doable if you have an NA MR2. The 1996 5S-FE Camry was OBD2 and was available with a 5spd. You just need the engine harness and 5MT ECU from one of those, and you'll have to repin the connector at rear junction block. Worth it? Probably not, but totally doable.
A 96 Camry 5spd is a one-year only OBD2 variant before the 5S underwent some major updates for the 1997 refresh. It's exactly the same as the engine in your car, except the Camrys had a balance shaft.
If you're going to the trouble, I would throw a V6 in there and you get the OBD2 for free.
I can't speak intelligently for the MR2, but you'll have to do a deep dive on the process. In many applications, it's not just sensors and wiring. Some cars need surgery. Often times there are reluctor rings that went from magnetic to optical, or from 8-tooth to 24-tooth. Subtle changes to mounting bosses for sensors, injector impedance, and addtional sensors for which the OBD1 assembly has no provision could be some things you encounter.
Wow, a necro thread! That I created!
As others have said here, I think that, ultimately, a standalone is where I'll go with my MR2. Not now, not anytime soon - Wake costs a lot of money, next 2 years will be paying college tuition!
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