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Help a Newbie Out

Posted: Fri Jun 26, 2020 6:44 pm
by Fredman6
Hello All, I've been using HLT on my iphone 6 along with an old original GoPro Hero HD for many years and that's worked fine. This year I decided I would up my game and I added a new GoPro Hero 8 and a Kiwi 3 OBD adapter. I used this setup at Laguna Seca this past weekend and my end results were not what I had expected. I've been searching the forums all day and I think I've found out why, but want to confirm here.

Here's my setup:
iphone 6 running ios 12.4.7 (latest available)
HLT Grand Prix Edition, v23.0.11 (latest available)
GoPro Hero 8 (latest available firmware)
Kiwi3 OBD (latest available firmware)

I set HLT to use only the GoPro 8 camera (no phone camera being used), and HLT did automatically start and stop GoPro recording for me. I setup everything before heading on track and never had any errors or warnings reported.

My findings that I didn't expect:

1.) External Video and Data out of Sync:
HLT is recording the data and controlling the start/stop on the GoPro; I expected the two (video & data) to be in sync or very close. When I overlaid the data onto video (I tried both Dashware and Race Render 3) I found the data lagged behind the video by 3.6s to 3.9s varying with each session recorded. Is this the normal expected result? If not, is it simply my iphone 6 is too old and sluggish now?

2.) Slow OBD Updates:
I didn't use the RPM or Throttle Position data on my videos because both were so slow. When watching them overlaid onto the video, they were slow to update compared to what was happening in real-time on the video. What would be the cause for the slow OBD RPM and Throttle data? Again, is this down to a slow iphone 6? I had no errors or warnings in HLT when making the recordings. I did read this morning that the data is captured at the same rate GPS is captured. Since I'm using my phone for GPS, is this the reason for the slow RPM gauge? I assume the solution is to get an external GPS sensor? Will the Bluetooth Dual XGPS 160 work in conjunction with the Kiwi3 OBD Bluetooth device at the same time on iOS? How have folks been securing the GPS sensor in their car? Mine is a street car, I don't want to tape or glue anything to the dash.

3.) Less OBD Info:
I was excited to see what OBD information could be overlaid onto the videos. It appears the only data captured that you would use for a video is RPM and Throttle Position. I expected to have Brake input as well and was disappointed to see it's only guestimating brake by using negative Gs. I've now read on the forum that Brake input is not a captured OBD parameter.

Thanks for any help/advice. I'd like to tweak my setup for the next track day.

Fred

Re: Help a Newbie Out

Posted: Sat Jun 27, 2020 8:28 am
by Harry
1) When using an external overlayer, you will be responsible to sync data and video yourself. Video starts and stops will be in the range of 2 to 3 seconds "behind" data due to various runtime effects. LapTimer (tries) to compensate this when overlaying, but external programs have no idea about the specialities of recording conditions.

2) LapTimer interpolates OBD data to storage rate (usually set by the GPS), so this should not be the source for "slow". I suggest you check the OBD update rate you see in realtime: connect everything with engine running and check the rate in Administration / Sensor List or Engine View.

3) Braking pressure is not standardized because it is irrelevant for emission tests OBD is designed for. Some cars allow the use of Custom PIDs and LapTimer supports theses. Only in case no brake pressure is measured, values are simulated. Provided you have your car's details entered, this is often sufficient quality for video overlays (and better than nothing).

- Harry

Re: Help a Newbie Out

Posted: Mon Jun 29, 2020 8:48 pm
by Fredman6
Thank you for the reply Harry.

1.) Understand, video and data do not start at the same time. Thank you.
2.) I will check the rate in the app as you suggest and report back what I find. If I were to get an external GPS sensor, would this increate the OBD update rate?
3.) I have a 2006 Porsche Boxster S, I have not looked into or played with custom PIDs. Thank you for the explanation.

Fred

Re: Help a Newbie Out

Posted: Mon Jun 29, 2020 8:55 pm
by Harry
2) The OBD rate will not be increased when adding a higher update rate GPS.
3) I'm not aware of public information on custom PIDs for Porsches. But I'd love to get my hands on them!

- Harry

Re: Help a Newbie Out

Posted: Tue Jun 30, 2020 1:28 am
by Fredman6
Good Evening Harry,

I checked the OBD rate and it appears to be updating at 1Hz. Is this the expected rate?
Blipping the throttle, I noticed how the data reacted/updated about a second later on the real-time screen; that's similar to the delay I see when I overlaid the recorded data onto the videos. Is there nothing else that can be done to get a faster data rate from OBD?

I've attached a couple phone screenshots I took.
IMG_5721.PNG
IMG_5721.PNG (127.12 KiB) Viewed 101 times
IMG_5722.PNG
IMG_5722.PNG (229.46 KiB) Viewed 101 times
IMG_5723.PNG
IMG_5723.PNG (73.58 KiB) Viewed 101 times

Thank you again,
Fred

Re: Help a Newbie Out

Posted: Tue Jun 30, 2020 6:06 am
by Harry
That’s a pre-CAN bus protocol, you will get one or two Hz with them, not more. The on-screen delay is due to runtime effects, it simply takes that long for the data from a change in reality until it arrives in LapTimer. In general, using OBD is not too much fun for pre-CAN cars. :-(

Harry

Re: Help a Newbie Out

Posted: Tue Jun 30, 2020 6:49 pm
by Fredman6
Wow, I wasn't expecting that answer seeing my Boxster is a 2006. I thought all Porsche's 2003 and newer all used CAN Bus, which sounds like that is partially true, but they didn't use CAN Bus protocol on the OBD connector. I found this info on the AIM website which confirms Porsche didn't start using the CAN Bus protocol on the Boxster/Cayman until the 2009 model year. Looks like I'll skip capturing slow OBD data for my car. :( I don't see any reason/benefit to continue to capture OBD data during laps when the data's so slow.
OBD.JPG
OBD.JPG (88.66 KiB) Viewed 80 times
Thank you again Harry.
Fred

Re: Help a Newbie Out

Posted: Tue Jun 30, 2020 7:15 pm
by Harry
Good point, but the protocol negotiated is ISO4141-2 according to the snapshot...

Re: Help a Newbie Out

Posted: Tue Jun 30, 2020 7:29 pm
by Fredman6
Harry, see my new edited response above. You are correct. Porsche doesn't use CAN Bus Protocol at the OBD connector in the Boxster/Cayman until 2009. Based on that, I will stop using the OBD to capture data during laps, too slow to be useful.

Thank you for your help.
Fred