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Thread: OBD Speed is incorrect in TrackAddict but Correct in RaceRender

  1. #1
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    OBD Speed is incorrect in TrackAddict but Correct in RaceRender

    Hello!

    Just started attending track events in my Focus RS. I recorded my first outing but I am experiencing some strange behavior.

    The first thing, and the one that prompted an account to ask:
    When viewing the videos in TrackAddict on my phone, the OBD speed is WAY off. It has me doing 5-6mph when I'm doing 30-40, and then goes the other way as well, sometimes showing 60-70mph when I'm only doing 50. I thought it might be because I do have one of the generic $15 OBDII adapters, however, if I export that video to my PC and watch in RaceRender, it's spot on. Any ideas what might be happening there? Not a super big issue since it works in RaceRender.

    The other thing I've noticed is that my throttle indication, even if I select percentage, it doesn't accurately reflect the current throttle position. When I finally hit WOT coming out of a turn, it jumps up, but then settles back down to about 50%, even if I'm on the long straight where it's 100% floored for quite a bit.

    One last thing, I'm sure this is in the documentation somewhere, but I haven't been able to dig it up yet. In TrackAddict, I can Gear+1 to accurately reflect the gear my car is in, but when in RaceRender, I can't quite figure out how to do that.

    TIA!

  2. #2
    HPT Employee Weston@HPTuners's Avatar
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    Quote Originally Posted by 55D_RS View Post
    Hello!

    Just started attending track events in my Focus RS. I recorded my first outing but I am experiencing some strange behavior.

    The first thing, and the one that prompted an account to ask:
    When viewing the videos in TrackAddict on my phone, the OBD speed is WAY off. It has me doing 5-6mph when I'm doing 30-40, and then goes the other way as well, sometimes showing 60-70mph when I'm only doing 50. I thought it might be because I do have one of the generic $15 OBDII adapters, however, if I export that video to my PC and watch in RaceRender, it's spot on. Any ideas what might be happening there? Not a super big issue since it works in RaceRender.
    This is most likely a difference between the OBD and GPS reported speeds, with one app using one and the other app using the other. GPS speeds can jump around like that if there's poor signal conditions (in which case your driving line data might look a bit rough too), and OBD speeds may do similar if there's communication or compatibility issues with the OBD-II adapter or vehicle. In TrackAddict, most everything will be based on GPS speeds, although its in-app video player can be switched to show the OBD speed instead.

    In RaceRender, it should default to the OBD speed (tends to be better for detecting gearing), but you can switch between the two by double-clicking on the data file in the "Input Files" list, going down to the "Vehicle Speed" selection, and choosing a specific data field... The first speed in the list will be GPS, and the second will be OBD.


    The other thing I've noticed is that my throttle indication, even if I select percentage, it doesn't accurately reflect the current throttle position. When I finally hit WOT coming out of a turn, it jumps up, but then settles back down to about 50%, even if I'm on the long straight where it's 100% floored for quite a bit.
    Assuming the OBD-II adapter and vehicle ECU are reporting properly, this is likely the actual throttle plate position, rather than your throttle pedal input. This was simpler with the old cable throttles that were a direct relationship to your throttle pedal input, but in many modern vehicles, it can have a mind of its own... the engine computer is using your throttle pedal input to determine how much engine torque output it thinks you want, applying various other adjustments to that, and then commanding the engine controls accordingly.

    The best way to overcome this is to change the OBD channel selection to one of the Throttle Pedal options, assuming that your vehicle offers this. What's available for this varies widely between different cars, so that's why we don't have it selected by default.


    One last thing, I'm sure this is in the documentation somewhere, but I haven't been able to dig it up yet. In TrackAddict, I can Gear+1 to accurately reflect the gear my car is in, but when in RaceRender, I can't quite figure out how to do that.

    TIA!
    In RaceRender, double-click on the data file in the "Input Files" list, go down to "Transmission Gear", and there's an "Adjust" setting to the right... If you set that to 1, it's the same as Gear+1 in TrackAddict.

  3. #3
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    Awesome, thanks for the response!

    Quote Originally Posted by Weston@HPTuners View Post
    .... although its in-app video player can be switched to show the OBD speed instead.
    This was with OBD speed selected in the app video player on my phone. GPS was all over the place due to heavy overcast and nearby stormclouds.

    Quote Originally Posted by Weston@HPTuners View Post
    Assuming the OBD-II adapter and vehicle ECU are reporting properly, this is likely the actual throttle plate position, rather than your throttle pedal input. This was simpler with the old cable throttles that were a direct relationship to your throttle pedal input, but in many modern vehicles, it can have a mind of its own... the engine computer is using your throttle pedal input to determine how much engine torque output it thinks you want, applying various other adjustments to that, and then commanding the engine controls accordingly.

    The best way to overcome this is to change the OBD channel selection to one of the Throttle Pedal options, assuming that your vehicle offers this. What's available for this varies widely between different cars, so that's why we don't have it selected by default.
    I kind of figured that might be what it is, thanks for the confirmation and I'll look for the pedal input as a potential work around.

    Quote Originally Posted by Weston@HPTuners View Post
    In RaceRender, double-click on the data file in the "Input Files" list, go down to "Transmission Gear", and there's an "Adjust" setting to the right... If you set that to 1, it's the same as Gear+1 in TrackAddict.
    Perfect, thank you!!