Keep Tabs On Your Car Without OBD-II

[Steve] let us know about his MultiDisplay car monitoring system. Unlike traditional systems that rely on interfacing with the OBD-II protocol and existing car computer, the MultiDisplay uses an Arduino and custom shield with a combination of sensors; including temperatures, pressures, throttle, Boost, and etc. The data collected can then be displayed on a 20×4 LCD or streamed to a PC with visualization and event recording.

It’s nice to see half a years worth of work finally be complete and presented in such a clean and professional manner, keep up the good work [Steve]

37 thoughts on “Keep Tabs On Your Car Without OBD-II

  1. Just hook up a megasquirt in piggyback configuration for a couple of hundred dollars, you get the same output options and then get the added bonus of beign able to control your cars tuning should you wish to!

  2. I’m wondering how the narrow-band lambda signal is converted to a value. Maybe he’s lucky and his car’s ECU gives an analogue output, but afaik if you monitor the signal directly it’s essentially binary (too lean, too rich). There doesn’t seem to be much on it in the wiki.

  3. While the work looks great, the design behind it is questionable. There is no reason not to use OBD data. Its free, easy to interface with, and gives you all the information you have with this system, without all the extra hardware.

    Also, SMT pwns through hole. Make a real board.

    1. Not all cars have had their OBD data fully hacked, and some pre OBD2 are difficult to hack, since there is no standard for the information on any OBD diagnostic connector. Look at the OBD1 North American GM EFI, I have a file with over 300 files of datastream definitions.

    2. Armchair-engineers running their mouth again…If you don’t know what this is for and why you need it, you don’t need to be redesigning this guy’s circuit. Real working boards pwn imagined superior boards. Make a REAL post next time.

    3. Also some people have cars that are pre-electronic management of any kind, and something like this would be very useful for providing accurate data, instead of relying on vague liar instrumentation that is 60 years old…

  4. Um MS in piggyback? that is a very stupid thing to do. Having TWO ECM’s trying to control injector pulses will cause big problems. Sounds like someone does not understand car fuel ECM control.

    Megasquirt is a REPLACEMENT of your car’s ECM. it does not piggyback and run with it. I know I have been doing custom ECM’s on cars for a decade, I even have one running a motorcycle for ignition timing.

    That said, most of what he is doing is really overkill. Some of that information is useless outside of tuning. Throttle position is worthless without base injector timing. I can get a ODB-II interface to tunerpro RT for real tuning. you can install a MAP sensor to get more useful information for what this display is for coupled with the RPM’s and ttemp sensors.

    It’s neat, but completely useless for anything but monitoring.

  5. fartface:
    Obviously you don’t have that much experience with custom ECMs. Tons of people do a piggyback-esque MS installs. Typically they leave the stock computer to manage spark, cut the injector wires leading to the stock ecu and rewire to MS. Typically this is done to “maintain” emissions compliance, so that when you go to have your car inspected they can still plug in and pull info from the stock ecu through OBD-II.

    But seriously, this project is retarded and overkill.

  6. Hello,

    im running this and the questions are the ones i hear quite often ;)

    MS: its not legal, as it does not give OBD Errors i would fail emissions and a at a police check i loose my license plate…

    Narrow Band Lambda: yes my 1996 car has a narrow band, what is enough to see trouble but not enough to check the fine tuning. but things like the LM1 Lambda (0-5V programmable output) make tuning possible. its super easy to attach to the MultiDisplay and get perfect readings.

    OBD: to slow, not all signals. most ECUs update at about 1-2Hz, there is no way you can see overboost during shift or see whats happening during a high speed shift (drag racing). im updating at 30hz what shows every little detail during a shift.

    Yes, mostly its overkill, it all started with the idea that i want to know whats going on in my tuned engine and it went a little beyond…

    You dont have to build every part of it, depending on what you want to see just small things kann be taken, for example:

    1. So would this work for something that doesn’t have ODB yet? I’m in the process of getting a DeLorean (yes, no negative comments please), and would like to not only have a more reliable system, but be able to hook up to something like the nVidia digital instrument cluster solution (which can be customized for look and feel). I’m most likely going to stick to the PRV, and add the megasquirt (a number of D owners have done so no problem).

  7. @nes
    “. . .afaik if you monitor the signal directly it’s essentially binary (too lean, too rich).”

    While it is true that the sensor is inaccurate away from stoichiometric most ECU’s in closed loop measure how many times a minute the O2s passes the midpoint, necessary to keep the Catalytic converter lit off with fuel and oxygen alternately.

    Since the car needs to run at 14:7 (stoichiometric) the only reason for a different type of sensor is acceleration enrichment tuning, which can be done seat of the pants, or trial and error. Obviously this system doesn’t offer that.

    I too am curious as to why he didn’t purchase a kit from DIYautotune, they are only $140

    You can also control the spark with MS, it supports many kinds of Coil packs, dizzys and COP systems

  8. Seriously, *chill out*.

    I don’t think “Steve” claimed his project would solve all the world’s problems, so why are you being so harsh?

    No offense @fartface, but stop and think for a moment about what you actually said… that this monitoring system “… is useless for anything but monitoring.” Duh. That’s like saying your glasses are “useless” for anything but lookin’ through.

    And you, @trey… I don’t disagree with your initial comments that reading OBD might be a cleaner approach to monitoring an engine, but does that really make this project “retarded?”

    Since you can’t see the value in this project, let me explain it to you.

    (1) “Steve” came up with an idea and turned it into real hardware. That alone should serve as inspiration to all those who post here to crap on other people’s projects, but never seem to get around to building anything themselves.

    (2) I’ll bet money that he learned a lot about processors, coding, and handling mixed signals. Anyone who attempts to replicate his device will learn similar lessons.

    (3) Somebody else may look at what Steve has done, and decide that his gizmo is perfect for their non-automotive data collection application. @trey, you can’t use OBD if the article you are monitoring doesn’t have OBD.

    (4) Somebody may look at what “Steve” has done and decide that *parts* of his system might be useful for a completely unrelated project they are building. If borrowing bits of technology from one system to integrate it into another unrelated system is not hacking, I guess I don’t know what is.

    Some people bitch about Hackaday not posting enough real hacks, and yet, frequently when something is posted, the author is lambasted for his “retarded” or “useless” project. What incentive does someone have to share their work when they can expect that kind of attitude?

  9. Thanks Hack A Day!

    I’ve e-mailed them the past weeks for a project like this. Glad to finally see that it’s here. I’m building something similar, but I didn’t have all the info I needed to complete mine. This is a pretty interesting concept none the less.


  10. pookeye, thanks for your true words :)

    didnt laugh so much for a long time reading the comment on fartface *lol*

    about 2: OH YES!
    ive learned a ton of things, from coding to layouting and even documenting.
    i recommend to do this to everybody, make it once and you will see a lot of things in a different way :)

  11. “Um MS in piggyback? that is a very stupid thing to do. Having TWO ECM’s trying to control injector pulses will cause big problems. Sounds like someone does not understand car fuel ECM control.”

    Umm someone has designed one from scratch and works with them on a daily basis, thanks ;) You can easily piggyback an MS, just (rather obviously I thought, but clearly not!) leave off the injector driver connections.

    “MS: its not legal, as it does not give OBD Errors i would fail emissions and a at a police check i loose my license plate…”

    Sure, but you don’t have to run it as the soul ECU, thats why I said “at a later date, if you want to”

    My point was simply that if you wanted a cheap and easy solution to monitoring most of your normal engine parameters, and even control some or all areas (like boost, even if not fuelling) you can do so in conjunction with your stock ECU. I spent 2 years driving round with the MS monitoring my stock ECU to map out actuator trip points, actual AFRs, knock levels etc. Then I modified it slightly to take full control of fuel and spark and tweaked the firmware to work better on my application.

    Sure it doesnt have 8 EGT inputs, I’ll give you that, but it does have 1 which is plenty in the majority of applications.

  12. Perhaps it’s over-kill, but that’s often just a result of enjoying what you do. You see what limits you can push. I say, good hack Steve!

    At least they didn’t give you crap about using the Arduino…. heh

  13. @capn; thanks! What a useful couple of articles. I also just read their papers on EGR valves. Interesting stuff.

    I am considering replacing the carb on my ’72 vehicle with a closed-loop single point injection (just as many manufacturers did with their existing engines around the mid ’90s when catalytic converters were mandated in several territories). Always on the look-out for useful info.

    I don’t want to run a MegaSquirt, mostly because the crucial bits of the design, such as the closed-loop fuelling are apparently proprietary. :-(

  14. Steve,
    Nice board, but I have a couple of concerns. Firstly, why an arduindo shield? You could save a decent chunk of money by burning an ATMEGA with the bootloader. Second, How vibration-resistant is this? Last, you should look into a conformal coating from MGChemicals or Kester, or something to keep the electronics safe.

  15. to all the haters out there:

    my 71 opel gt DOES NOT HAVE an ecm. this solution allows me to digitally monitor and record my engine and car condition without any external modifications aside from a vss mounted in one of the tires.

    This build will be going into my GT verbatim minus boost and thermocouple solutions as i really don’t need them… but i will be adding a air/fuel mix monitor.

    I think its an incredible demonstration of arduino application in a real world scenario, and his problem solving of the mixed sensor array is inspiring.

  16. exactly… not everyone drives a car with payments (new cars)… some people also drive cars older than 35 years that have no electronics beyond the radio. Been off and on helping a guy restore an original Ford F-1 pickup with a 6V system (all of about 8 wires for the entire truck). It doesn’t even have a radio in it. If you wanted to monitor anything on that truck beyond the dash gauges, you’d have to add it to the truck.

  17. OBD 2 data is complete crap for actual datalogging as the samples per second are complete junk. It was never meant for tuning purposes on a car, but for diagnostic purposes.

    This is actually a really cool hack and I would buy this guy a beer for making this.

  18. St.Jimmy, its an Arduino shield as i was to lazy to make it directly…

    if i would do it again the atmega would be directly on the board.

    im running it now for some weeks and have no problems with vibrations, all the ic´s sit in the nice sockets not the cheap ones and they work good.

    for a real sales product some redesign would be good, but as the people who make will drive it know what they do its ok like this :)

  19. I did a lot of work with the OBDI interface about 8 years ago before GM was going forward with the 42Kb/ps (or about that speed). A standard bit bang won’t touch that speed. I remember it needing a hardware assist (Verilog). But the most awesome thing is, is that a while back, a lot of the specs were posted, and I put it into a binder that I still have before they pulled the specs from the inter net. It’s all in paper form, but I still have it.

    If anyone needs info, or just get stuck, feel free to contact me at

  20. BTW, what I found, is that specs cost abou5 $5k. Congress made it legal for everyone to own the rights to diagnostics… but, as I found, it was a pretty penny. I was actually after the ‘dead cylinder’ test. that was a long time ago. Perhaps the cost of the spec is much cheaper.

  21. I haven’t read all the comments yet, but can this be used on my Honda CT110 motorbike, which doesn’t have fuel injection, nor OBD, nor ECU ?
    I’d like to have a MPG meter, plus whatever else I could get, but MPG tracking & logging for different speeds & angles of incline would be desired. Thanks. I am happy to install a fuel flow sensor. Or can it be done by the CDI spark timing? Is a set amount of fuel delivered, each time the CDI sends a signal to the ignition coil ?

  22. if you can read the throttle position and rpm, you should be able to figure out the fuel consumption from your carburator.

    a fuel flow sensor would be even nicer, giving you the highest accuracy!

  23. Well done steve, there are always people out there ready and wanting to knock your work, any monkey can type a message but you have to think for yourself to write/debug a program.

  24. Steve, thanks for doing this. It never ceases to amaze me how many AH’s there are in this world that never have anything good to say about anything. My vehicle also does not have OBD at all, and I’m only going to interface a few sensors- fuel level, volts, tempx2, & pressure and put them on a 4×20 LCD. Your work has saved me a lot of time and answered a few questions I had about the sensor interface.

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