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just what can these babies do?

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  • just what can these babies do?

    alright I see they have speed, rpm, throttle position ect.

    but can they calculate these figures...

    for example, with speed and time, they can calculate acceleration. with acceleration, coefficient of drag, and weight, they can calculate HP(peak, or any amount under peak that your using at that precise time). while their at it, how about performance numbers like quartermile and 0-60, 5-60, 30-50, 60-0 ect ect ect.

    how about saving a log of speed for a rolling 20min window.(might be useful if you get a ticket or accident to show you werent speeding if it applies, or to show speed around a track, pinpointing areas that you did better on before)

    seems like with all this info straight from the source, you could do alot of things. perhaps some nice eye candy while we're at it?(that one screen shot was a bit "blah" if you will)

    just thinking out loud of some what-ifs and how plausable they are.

  • #2
    in theory yes

    most of the software doesnt have this as a feature

    also persise time is going to be limited to with in a second

    as i understand it the obd-2 can only provide 1 reading at a time

    so you cant get two readings ( like engine load and speed) at the same time so its hard to compute acuratly the hp and other things. but im sure it can be done

    right now im working with the br-3 software to try to get it loged into excel in a workable format so that you can do some computations.


    • #3
      well 1 at a time might be ok, as speed is the only thing it really needs.

      but youd need time down to atleast .1 preferably hundreths.

      why time down to only a second? is that as fast as it can update? thats too bad.


      • #4
        when i set mine on turbo i can usally get about 3 readings a second

        but that still not a .1 diffrnece


        • #5
          This software has user defined real time equation editor. Included are HP, G force, and MPG but it sounds like you can add calculations for any sensed data.
          Also GPS data and stop watches. I haven't had time to play with it yet.


          • #6
            do you know if that will work with the BR-3?


            • #7
              I can get about 22-23 readings per second (VPW) from mine but to get 23 speed readings per sec I couldn't get any other info. I'm really interested in doing MPG. Can anyone help me? Is it calculated from load, RPM, throttle pos?


              • #8
                22-23 would be plenty to get pretty damn accurate numbers accross the board. I just played around with that other sites software under the sample. would the 2 be ok together? work with the others hardware and whatnot.

                or is there an even better personally written software program that could be used?


                • #9
                  Probably not. The Multiplex-Engineering one isn't just a pass-through. You send it commands and it returns responses. I would think the others could do this just as fast though. My app only works with that one, I just don't want to support it so I don't tell anyone about it. I'd be willing to give out C++ code for it though. Mostly I just use it for fancy graphics. You can make guages and dials and all kinds of other neat things as well if you write your own app.


                  • #10
                    yeah, I dont have much programming knowledge to make my own, or understand someone elses.

                    Im so needy . I want a setup that will let me recieve atleast 10updates per second with 1 variable, even better if it can do 10/sec with 2 or 3 inputs. I want to be able to enter my own formulas using this data, and I want a pretty little interface. and I dont want to program it(cause I cant). oh and Id love it if it logged some stuff in a rolling log with a 1 or 2min window, but thats not so important...


                    • #11
                      I'm surprised nobody's chimed in on this. There is a lot of OBD-II interest and customs software discussion on here. I did a little graph today just to add more to a tech show-off screen <attached>. If you wanted to do draw some graphics and write javascript I could help you out. This screen is all javascript, sort of.
                      Attached Files


                      • #12
                        Regarding speed of data capture via OBD2 - the vehicle responds to a serial request / response sequence. If you are trying to pull many different data types, it will limit the maximum number of updates / second any given data element is provided. This is a limitation of the vehicle data buss and not usually the limitation of the interface box or the control software. But for any practical purpose, it's plenty fast enough.

                        CAN protocol should make data updates significantly faster (a few current model year vehicles so far).


                        • #13
                          I have no clue what my exact "protocol" is. Id actually heard my car actually had OBD3... not sure if thats obd2 compatable, but I know people have used OBDII diagnostic units. I drive a 2003 350Z if that helps any, prolly not.

                          I have done 2 years of C++ programming, but I assume I dont know much because I never did anything graphic, it was all text interface. and never took input from anything but the keyboard, no idea how one goes about decoding info from a serial port. then beyond that, though I could derive a formula for HP and quarter mile from speed and time alone, I wouldnt know how to implement it with the program.

                          I have the PC now, and I find myself staring at some sort of visualization, which is useless, but if instead of a visualization it was some pretty gauges, and test data, showing current HP used, throttle position, speed, load, RPM. the refresh rate on all that wouldnt really matter.

                          then go to a performance mode, where it could record HP based on speed alone, keep a log of speed and acceleration from speed and time.

                          input the gear your in (and the gearing for that gear) and it can find the RPM indirectly, so you could do a 2nd gear run and get a full dyno plot from acceleration, weight, drag, wheel drag. along with RPMs based on the speed each point was taken at.


                          • #14
                            alright, imagine this is you will. remember Im not a programmer, so my ideas may be off the chart in terms of realistic goals.

                            the photo below shows general ideas, but heres the details, up top you have a overall chart of stuff.

                            vertical boxes are graphs like you have. even a digital readout would be fine. smaller circle gauges with a gauge and a digital readout under them would just look awesome, but trying to keep things simple... heh, I failed. volts and both temps can be on a 10-20sec update cycle, they are not needed to be extremely up to date info, though if update cycle was user defined, thatd be awesome. of course, updates probably arent on a per second basic, rather for every 10 of these requests send one of this request, or so I would assume. but none the less, these are measured far and few between, voltage even once every minute would be plenty. mainly there for eye candy, my car, and most others have a gauge for this already.

                            alright, to the important stuff. speed and RPM. these you would want updated often, maybe 3 speeds for every RPM, unless your signals per second was just high, then you could go 2:1 or 1:1; the idea is that you want accurate speed above all else, atleast 10per second ideally, so if you can have 20 readings per second you could go 1:1, but if only 15, then go 2:1 ect. not a reactive type thing, Im talking you know about how many reading per second you get, and set it accordingly.

                            gear, thats just cool... you input your gear ratios, quick equation registers which gear ratio would get the correct speed for that RPM. find the closest answer, highlights that gear. again, this is eye candy, shouldnt tax the OBD connection any, just an easy formula that looks cool.

                            now the bottom half... thats the good stuff. on the right you have a list of potential info, EX. HP, speed, RPM, Torque, GForce accel. most come from speed, except RPM which would of course, come from RPM. being that your getting atleast 10readings per second of the speed reading, you have a nice curve, which cycles in a 20sec window to look at. you should also be able to suspend the window, or set it to log 20sec and stop. 20sec should be enough time for example to start it and go to 60, or start it and finish a quarter mile. perks would be if it could read out the point which you reached 60mph, and the speed and time where you would have traveled a quarter mile using a simple calculus equation of the graph. though not derivitives as you dont have the formula of the graph, but break it down to each data point, and say from .1sec to .2sec the speed was 3mph then figure out how far you went in .1sec at 3mph, then .2-.3, and figure out how far that was, add them up and up till you hit a quarter mile, and thats the time and speed.

                            wow this was a long post, and I could go on and on, but Ill stop here and hope someone actually reads this. I cant program, but Id be happy to do some technical advising with formulas and idea generating. if this software happened I may even know a guy who would be interested in selling it, not to mention Im sure whoever wrote it could sell it themselves.
                            Attached Files


                            • #15
                              OBD-III looks to me like OBD-II with a lot more information. I don't know if it's compatible though. When you decide on an OBD interface, just ask the company if it's compatible with your car. They usually know about all the cars out there. As far as programming, serial I/O is almost as easy as file I/O. You open a file handle and write some bytes, then do some waiting and read some bytes. For OBD-II, you write like 5 bytes, get some back and do a little simple math. That's it. Learning what those bytes are can take some time. GPS is even easier. I think you could do it. When you're just starting out, graphics can have quite a learning curve though. Like with Windows, you have to learn a big API, but once you get past that it gets easy, and besides, there are millions of examples of windows code on the net.