questions on my data

i put a start/finish line in on a little loop i drove. rc gave me some laptimes. upon export however the lap data all appeared to be n/a.

this is not that dump, but a previous dump:
here is a vid i made:

why is the lateral g's graph pegged to the right? was my data bad? or did i just source that data wrong from the file?

i thought i added some things to pick up on the obd2 data that didn't get exported. like throttle was one and throttle % was another - i see the % here but the other is not? also what does the primary/secondary mean for the obd2 config?



  • edited April 2009
    Hi, you need to export "all laps" instead of "traveled route" to get the lap info. That should fix the first issue.

    Not sure about the lateral g's though. RaceChrono calculates them from GPS data so they should be in center in average.

    Only RPM and Throttle% are currently exported in CSV, but I could add some other important ones as well (but not all), if you have a list? High priority channels mean they are requested as often as possible. Low priority mean they are requested ten times less often than the high priority. Notice that this bandwidth is shared with all channels, so adding more channels will make the resolution worse.

    BTW: Is ChaseCam working on RaceChrono support? If so it might be useful have them contact me, and we could work out what ever format we like, xml, binary... Also could have all OBD-II info (CSV is a bit inconvenient for that).
  • edited April 2009
    yes looks like Chasecam is working on it let me see try emailing this guy:
    <removed email>

    It would be awesome to have the 2 work together flawlessly
  • I'll contact him, thanks for the email address. I removed it so he does not start receiving spam.
  • only those 2 fields get exported? i was looking for boost, didn't find it, somebody told me to look for relative manifold pressure. i haven't gotten back in to obdkey with race chrono to look for this yet, but i definitely want to export it! :)

    what about speed? i thought i read somewhere (here?) that obd2 speed would be more accurate than gps speed.
  • edited April 2009
    Well not all cars support the boost reading, but if they do, relative manifold pressure channel should work. Once you have one session recorded with boost data, please send the session NMEA file to me (tracks(at), so I can make the changes to the export format.

    Actually the OBD2 speed is not as accurate, but is more consistent. Meaning there is a fixed error in OBD-II speed (usually readings are a bit too high), but no GPS style random errors. For video use GPS is more than enough (rather save the bandwidth for other channels to improve resolution).
  • i see, thanks for the info. i will get some data to you with boost this weekend. :)
  • aol, i sent you some data from a 5/1 run. it has a few of the pressure metrics, i assume one of them is boost, or one could be calculated to get to boost? let me know what you find please! also when exporting throttle, is it throttle or relative throttle that is exported? i assume the latter.
  • edited May 2009
    Thanks, I will take a look at the data later this week! I think its the throttle, but I'd have to check that...
  • edited May 2009
    Yes, you have recorded the "Manifold pressure" channel which is the boost. You can view it your self by opening traveled route and "options > view next 15 mins", and then selecting the manifold pressure channel from "options > settings".

    The boost reading is measured in kPa units (this is how OBD-II reports it), and 100 kPa is 1 bar. I probably should change the units to bars and PSI at some point.

    You are getting values between 20-90 kPa, which is 0.2 bar - 0.9 bar. So the reading is relative to the air pressure. But I wonder if it's right, because I'd think you'd get negative pressure when lifting. The values correlate nicely with the throttle usage, so it is the right channel.

    You had recorded 4 channels as primary, which is in my opinion too much, as you seem to get only 4 channels per second (on some cars the number is closer to 10, but usually 3-4). So the resolution of each channel is more than one second.

    Can you do me a run with only two channels logged, throttle and boost?

    Thank you for the data, I will use it when I add the boost to the CSV!
  • edited May 2009
    so you always had it as positive? is it not subtracting atmospheric pressure then? i don't recall exactly what driving i sent you, but if i was sitting idle anywhere i would expect the boost to be negative as well.

    i believe the 05 sti does 14.5 psi stock max, i have a cobb ap stage 1 which i think raises it to 16 psi. i don't recall how i was driving, so i'll include that on the next log i make.

    it makes sense only to log throttle, rpm and boost as that is all that will be exported anyway correct? throttle rpm as primary boost as secondary? how about that? will make you a new log this weekend.
  • edited May 2009
    No, it definitely subtracts the the atmospheric (I guess right wording is "relative pressure"), as it is less than atmospheric (100 kPa). The high reading (~90kPa) from your log matches the 14.5 psi (~100kPa) pretty closely... Could be ofcourse the sensor is cutting the low end, so you never see those negative readings... dunno. But at least the high end is close to your number.

    The channels you log is of course compromise between update rate and different channels... your call :-) I would pick RPM and Throttle OR Boost for my videos. This way they both would be updated twice per second.

    RPM, Boost, Throttle and Speed should all be high priority channels, as these are update rate sensitive channels (lot of info that changes quickly). For stuff like temperatures etc, low priority is fine.
  • should i get obd speed or is that better from gps? boost, rpm and throttle too much on the priority channel?
  • edited May 2009
    Go with the GPS. It is the one exported and without it you save OBD-II bandwidth. Like I said I would pick two. Notice that Boost and Throttle are pretty much the same thing, as they heavily correlate... but pick what ever you like to have on your video, that's most important :).

    Notice that you can not use Boost on a video before I make some changes (also for RaceChrono2AVI some changes are needed).
  • yup i understand that boost won't be available until a new version can export it. i actually use dashware but the rc2avi looks quite good!
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