Low cost OBD-II Display
 

I've got a little time before I can delve into the RX-8 so I'm going to put together a low-cost OBD display to display coolant temp and possibly LT/ST fuel trims.

Anything else that you'd normally grab from OBD-II that you'd like to see? I should be able to decode anything that's a standard OBD message.

What platform are you building it around? I've built a digital gauge around an arduino to display signals from the fuel pressure, oil pressure, and oil temp sensors I added but I haven't gotten around to adding a CAN-BUS shield to pull OBD data (or put this data on the CAN-BUS so it can be read via OBD).

I think AFR/Lambda would be good for those running boost. MAF rate is useful for diagnostics but not necessarily needed all the time.

I'll probably end up with an arduino and MCP2515 or similar. AFR might be tricky as I assume everyone is using a different controller (the RX-8 has to have narrow band O2 sensors right?).

Rather than building a full logger I thought I'd focus on the info that 80% of the regular owners need. Can always add more later. From what I've read the dash coolant temp gauge is next to useless :)

The RX-8 has a wideband for AFR and a narrowband for cat health.

Pretty sure the PCM uses the standard SAE PID for it, too.

Ok I'll check it out. Thank you :)

I suggest, before you get in too deep, that you look at the Ultra Gauge. The ones I bought were about $60, one for each car. That would be your competition...

Everything critical can be read with anything that's capable of reading live data.

So ECT, LTFT, STFT, B1S1 Lambda, B1S2 Voltage, Cat temperature, etc. are all easy to access.

I was looking at a Shinka a while ago for someone else and the owner of that Shinka installed an OBD2 monitor in the dash. It's capable of reading live data and erasing codes(which he needs to do every once in a while since he runs a catless mid-pipe). Not sure about the details on it, though.

https://cimg8.ibsrv.net/gimg/www.rx8...8d99451b20.jpg

Interesting. I've got to do a timing belt on my truck this week but I hope to look at this pretty soon.

How low cost are you looking for?
Attached is my solution, while not dirt cheap I wouldn't refer to it has expensive either.

Also while we are on the subject, what are suggested temps to use for warnings for coolant and cat?

In my GoodBox I monitor:

- coolant temp and rpm (the 2 things I need to know with precision on the track)
- short term fuel trim and AFR
- intake air temp and something I don't remember

It can only display 2 things at a time, so those are the pairs I've set up. I would love to get cat temp as well, but GoodBox doesn't know about that PID :(

As for warning thresholds, I start to back off around 220F for coolant temp and I would start to worry about the cat at 1800F+, but the thing with the cat is that it will spike to that on occasion, and backing off often makes it hotter in the short term anyway. So I'm not sure I'd put an alarm on that, more just keep an eye on average temp.

Thanks Loki, I added those alarms to Torque this afternoon, I did add one for the cat temp but not as a high priority, I will modify it if I find it coming on too often.

Is it possible for me to clear the OBD II (OBD2) diagnostic codes manually by connecting or shorting certain pins together? If so, curious minds want to know. I do know that a command issued through a command line (mode 04 or >04 will clear the information) but I was hoping to find something a bit more simple such as shorting two pins together.
https://cimg9.ibsrv.net/gimg/www.rx8...eccaed0c37.png

I did mine for around $75. Bought a 7 inch amazon fire tablet, $9 Bluetooth obd-ii device, and a scoche mount. I rooted the fire table to add Google play. Then installed the torque app. Then put the mount right in front of the display for the radio. The 7 inch tablet fit perfectly. It almost looks like it belongs there. Kinda like the oem nav system. I'll take a picture in the morning.

Pics please ?

https://cimg4.ibsrv.net/gimg/www.rx8...282be0bfa9.jpg
https://cimg9.ibsrv.net/gimg/www.rx8...5278763286.jpg
https://cimg3.ibsrv.net/gimg/www.rx8...ec9831dde0.jpg

It is dark out, but you can still see it pretty well. I forgot I moved the mount above the display. It ended up being much easier to get to. There isn't much space in front.

Cheers ...looks spot on !

Thank you. It makes like so much easier.

is the tablet just using blue tooth to the OBD2?

Yes, it's just bluetoothed to the tablet. Sometimes I tether my cell phone to it for GPS or if the kids want to watch YouTube.

Even cheaper: I used an old mobile (Samsung mini) placed on a handcrafted stand, between the ceiling and the rearview mirror, using the Torque app and ODB2 via Bluetooth.

https://cimg4.ibsrv.net/gimg/www.rx8...fa15699af0.jpg

I use a theme with a black background, so I can use larger elements, being able to overlap them slightly. I use the standard PIDs, some of Torque's own and others that I calculate as extended data (such as selected gear).

If you look at the photos, I have organized the data on 4 screens and on all screens I show the selected gear:

1: Gear and Speed corrected, average consumption, Liters in tank, Km that could travel with those liters and instant consumption

2: Gear, catalyst and intake temp., admission press and engine temp.

3: Gear, Throttle Position, Measured AFR, Absolute Load, MAF, Requested Lambda, and Measured Lambda.

4: Gear, Ignition advance, LTFT, STFT and LTFT+STFT combined

I use an OBd2 module ELM327 Bluetooth V1.5 OBD2 HS-CAN / MS-CAN for Ford. It is somewhat more expensive, but it has the advantage that through the ForScan application it allows me to access the control buses of ABS, EPS, AIRBAG and others (I think Torque does not allow it). I do not recommend taking the cheap modules as they collide with the bus and produce many problems.

As far as I know, there's no way to do it just by shorting pins.

hey how can I get one?