RaceChrono with Qstarz Q818XT + OBD2 poor synchronization/lag

I went to Laguna Seca Raceway last week and used Racechrono to log data.
When I tried to do some video overlay using Dashware, I found that the GPS data and the OBD2 data(RPM, Throttle Position, and intake air and coolant temperature data) was off on average of 3 seconds.
The RPM and TPS trace is ahead of the GPS speed by about 2.3~3.8seconds.

The hardware that I'm using to log it are:
Samsung Galaxy Note 2
Qstarz Q818XT at 5hz dgps mode
ELM327 OBD2 Bluetooth

I did noticed on track that I had to wait a few seconds for the Racechrono to report the lap times after crossing the start/finish line, so I'm wondering if the GPS was being logged a few seconds late.
It feels like Racechrono is logging data at variable intervals and it's doesn't seem to be working so well.

I love the +/- Sector times and keeping lap times, but now I'm questioning the data's validity.

Torque Pro that I've used on some other sessions, although it could be lower in accuracy/data rate, I get consistent data and everything lines up.

I can provide the .csv files and whatnots upon request.


  • aolaol
    edited March 2014
    Hi, can you check the update rate channel for the GPS? Is it varying between 0-5 Hz? Also does it seem there are missing GPS updates here and there?

    I've seen other users having such problem caused by QSTARZ GPS having serious flow control issues. This throws off the RaceChrono's OBD-II synchronization, as the GPS updates are coming with a long delay.

    Try switching ON this GPS receiver setting: "RaceChrono > Settings > Device > Do not change settings". It has helped two others with this problem.

    Also can you tell me your Android OS version. So far problem has been exclusive for users with 4.3 or 4.4.
  • It's a stock Note 2 Android 4.3
    I'll go ahead and test it with a few changes in settings over the next few days.
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