Harry's GPS Suite Forum

Having what appears to be a slow/wonky OBD logging/overlay display issue. Test setup below:

v20.0.6 Grand Prix
Samsung Galaxy S7 (Verizon) running Android 6.0.1, stock OS, no root/custom ROM etc.
OBDLink MX
Skypro XGPS160
Test vehicle: 2013 Toyota Tacoma

With this setup and everything connected I'm getting around a 9-10hz refresh rate or around a total 35-40 PID/rate (if I remember correctly). So everything looks fine there. Just when I actually record a session, the vehicle speed, RPM, throttle, boost etc., gauges are all over the place. They will sometimes jump all over the place and/or sometimes just lag behind horribly. I had this issue with v19 as well on a different phone. But now I have v20 on a new phone and used it on multiple vehicles.... so I figured it was worth bringing up again on here (and pretty sure it's just not an issue specific to my vehicle or phone anymore). The XGPS160 was used and connected at 10Hz for all tests as well.

Here's a video of what I'm talking about. Just a simple test on the street where I go WOT, trans downshifts and I briefly accelerate. You can see RPM and speed jumping around strangely.

https://www.youtube.com/watch?v=U-tS03aK9O8

I also noticed another issue... when recording using the video "preview" mode, there is significant lag in the OBD data. I also noticed on the phone as this was recording it was extremely slow and choppy as well. Probably not a big deal as normally you wouldn't be recording laps like this, but figured I would bring it up as well:

https://www.youtube.com/watch?v=VjMrjF48NwI

I've had this same issue since day 1 which has been the big reason I haven't been using it primarily. Hoping to get this ironed out finally.

Do you get smooth readings while in Engine View and driving? Overlays are always based on peristent and interpolated OBD data - so it may differ from what LapTimer received initially. There is a known problem with certain GPS / OBD update rate combinations and interpolation - that's the reason I ask.

The video live view may combine some overload situations into the rate discussion, which is the reason I ask for the Engine View and not Video View. My Nexus 6 eg is not able to record a 4K video while displaying it and running all other LapTimer stuff in parallel. It is getting all choppy.

Can't watch the videos currently - low GPRS bandwidth here

- Harry

I will check out the Engine View only while driving-- it's a little harder to do while actively driving but I'll give it a shot. If I had to take a guess here it seems like an interpolation issue, there just seems to be outlier values that throw everything off. Attached is the .csv file and a chart with GPS speed, wheel speed and RPM plotted out vs time. The OBD data only goes crazy when there is a larger rate of change.

Not trying to make this a HLT vs other app debate, but I also wanted to throw out some data I got with another app doing the same test. If nothing else other than to show that I don't believe there is a hardware or some other strange issue going on with my setup.

At least it is clear these sparks are wrong. Two possible reasons: 1) data is coming in noisy 2) data is getting noisy during interpolation. The later is a known problem I need to go into. In case you see smooth rpm development in Engine or Speedo view, it is a proof it is 2). In case to is noisy in the Engine view too, it is 1) and an electrical problem.

- Harry

Yes, it is most probably 2, and it is easier to fix too.

- Harry

I will standby then until a fix is found/implemented. Let me know if you would like any other data/testing.

Well, that double confirms it. Just tested it, viewing only the engine page. Totally normal behavior, no spikes in any OBD data.

O.k., it is on my short list for bug fixes (only 6 left).
Please watch the release note of new releases (just uploading 20.0.7). Once you read something like "Fixed OBD interpolation", please try again and let me know if it works.

- Harry

Aaron,

I have your exact same setup although I have an LG G3 phone. I had this same issue with very spiky OBD data, until I fixed the OBD delay in expert settings. I believe the default is 1.0 seconds; my OBD delay is set at 1.8 seconds.

Using Excel, export your data, and you may find a difference in GPS vs OBD speeds. Create some formula's if you want or just 'eyeball' the data to find what rows the GPS and OBD speeds match. In my case it was .8 seconds later. I then created a formula to pull an obd speed that was 0.8 seconds later and compared to GPS speed as verification. It won't be perfect, but close. From there I added the 0.8 to the 1.0 default setting to arrive at 1.8.

After "tuning" the OBD sensor delay, my OBD data is ultra smooth. Not just speed, but RPM and throttle as well.


Ed