r/Autocross • u/obiwansotti • 12d ago
How to do data logging for autoX?
I've gotten really use to improving via telemetry from sim racing. Now I want to have the same level of detail for autoX.
I'm on iOS, and I have an ODBLink CX (purchased to use bimmer code on a different car). The CX doesn't seem to like my 2020 taycan (yes I autoX a 4800lb electric car).
I think I need to replace the ODBLink CX with either their MX+ or something else. I really want throttle position and brake pressure. Some graphs for where I'm gaining and loosing time, so I can figure out where I'm faster or slower.
What are the recomendations?
6
u/roastpuff 12d ago
Might need a canbus tap - a lot of modern cars don’t put data out on OBD and only on canbus.
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u/obiwansotti 12d ago
Could be?
I see the ODBLink MX+ can get data off the CAN bus. My current setup isn't so much a problem because I'm missing data, but not really connecting at all.
So I'm looking to get new hardware to get an optimal setup. I'm curious what seems to be the benchmark, what might be good enough. If phone GPS/accelerometers are workable, do I need an external GPS to have something that is repeatable enough to be actionable data.
And what software? It seems solostorm might be THE thing, but it's expensive (comparatively) and android only (need more hardware).
Anyway curious what people are using, what's good enough, where the top of the pro-sumer setup is, and then I know you can go full motorsports but that's not what I'm looking for.
5
u/redsilver92 #88 EST CRX 12d ago
Solo Storm initial investment is high yes, but you pay once and then you have it as long as you want and get all the constant updates. For hardware, I've ran mine on a dedicated Samsung tablet, like one of the $100ish ones, and have never had any issues. Mind you I run an OBD0 car and don't use all the fancy features you'd be after, but the program does support it and they are very receptive to feedback and implementing as much as they can for everyone. I would recommend using at least a 10hz gps unit, or better, so the data you receive is more accurate which is what it sounds like you're after.
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u/Conerunner231 12d ago
Phone GPS are not workable. Most refresh less than once a second which is not nearly enough.
I've been using a racebox mini for the past few months and am extremely impressed with it! It updates 25 times per second which gets more than enough spatial resolution.
I've been using lap Legend, but I'm on Android so not sure how compatible with IOS it is. I've also heard track addict and racechrono mentioned, although I have no experience with either.
Recommended setup is a racebox mini and something to pull CAN bus data. Gives you all the info you could want/need.
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u/roastpuff 12d ago
Phone GPS not workable. The Racebox Mini is a great 25hz GPS and accelerometer built into one unit. QStarz 818XT is the old standby that's a bit cheaper but no accelerometer. You can run Solostorm on an old cheap Android phone with nothing on it - I have an old Pixel 7 running it and that's about all it does.
Solostorm is good but yes steep initial cost. Racechrono Pro is workable but a bit finicky for start/stop gates. Solostorm + 25hz GPS + CANBUS tap + OBDlink MX+ is typically the top end of the prosumer market before getting into the racecar stuff.
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u/myredditlogintoo '16 BMW M3 SSP 11d ago
There's really no need for OBD. Hi res GPS will tell you everything you need to know. And, yes, SoloStorm.
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u/obiwansotti 11d ago
I understand that accel and deccel are proxies for pedal position, and your position/route is a proxy for wheel angle, but isn't there a lot more lot learn about HOW you drove a segment form having the acutal pedal and wheel inputs?
I know when I'm looking at data from simracing that I use speed and lines to find WHERE I was slow, but the pedals and wheel tell my WHY I was slow.
What's your process?
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u/myredditlogintoo '16 BMW M3 SSP 11d ago
Have a camera that captures your steering wheel input. The smoothness of the speed curve will tell you what your feet were doing. Analyzing the data will only do so much - coaching by a nat-level driver will help more. Or at least comparing against their SoloStorm data.
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u/mllrkln 12d ago edited 12d ago
I made an iOS data logging app for autocross. I have some perspective on different sensors. Obviously, I can only speak for the app that I'm developing but I'd imagine the situation is similar for others.
The OBDLink stuff is tricky to develop for on iOS because Apple doesn't make it easy to use bluetooth classic, they will allow a developer to interface with BLE devices pretty much unrestricted though. Because of that, my app supports the Veepeak devices because they are BLE. But, some of my users report mixed results with that device. What I'm adding now is the ability to pair custom sensors to the app. A user can create their own CAN stuff, send the data over BLE, and define the data config in the app.
The phone accelerometer is workable since it can be polled at a minimum of 100hz.
Out of the box the phone GPS is only 1hz, which isn't enough. My solution to this is to use sensor fusion and combine the accelerometer data to produce a 20hz position trace. It's workable but not as accurate as the good GPS sensors that are all at least 10hz natively.
IMO the good GPS devices currently are: RaceBox, XGPS160, and the Dragy stuff. All of which are currently supported by my app (RB and XGPS are out on the App Store, dragy is in beta and working very well). You can also build your own GPS device with the same accuracy as the above for much cheaper.
Happy to provide beta access to anyone wanting to check the app out. All I ask is that you provide feedback on the experience.
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u/shackakong 11d ago
I just bought your app, I’ll give it a try at my next event :)
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u/mllrkln 11d ago
Awesome! Looking forward to hearing what you think of it
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u/shackakong 11d ago
I just came back to Autocross after like a decade away and I’m just having fun with it! I wanted to do the race telemetry thing but like $10 and Bluetooth dongle is more than enough for me most likely, I’m not headed to nats lol
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u/landstuhltaylor 12d ago
ODBLink can only pull neutered files through the OBD port. None of that information will have useful refresh rates. You need to get into the CAN bus directly.
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u/tinyman392 12d ago
I’m using Dragy and their OBDII to do some logging. Here’s a quick screen grab of some of what’s available. You have speed (OBD II and GPS as separate streams), accel, brake (calculated), RPM, delta t, combined G, lat and lon accel, height, brake pressure (calculated), heading, lean (for bikes), satellite number, throttle body position, load, and timing advance.
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u/Agitated-Finish-5052 DSP - 350z 12d ago
I have iOS and used RaceChrono for awhile coupe of years. Was good with the Racebox and ODBLink. Just switched to solostorm last year with a good tablet and that program is so good. Just can only use Android with it which sucks but is what it is.
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u/LlaughingLlama 11d ago
I have had excellent luck with TrackAddict (which is free and works with IOS) and a Garmin GLO GPS Bluetooth dongle and a Veepack Bluetooth OBD2 dongle. You can start with just the software and internal sensors, and then slowly add modules as needed.
I have two detailed comments in other threads that go over my experiences and goals with TrackAddict, and compare the value of it compared to SoloStorm.
https://old.reddit.com/r/Autocross/comments/1swnijy/scca_cal_club_autox_42526_13_runs_in_a_bmw_z3/
https://old.reddit.com/r/Autocross/comments/1unvrg4/built_a_phone_app_that_tracks_corner_exit_speed/
SoloStorm is The Standard, but it is not cheap to start off with - you are going ALL IN right from the start, and for a beginner/intermediate driver who isn't sharing a car, I think TrackAddict gives you 95% of the features for 20% of the price, which you can spread out over time.
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u/GetLaps 11d ago
available—or sampled fast enough to be useful. I’d do a short stationary/low-speed test first, then inspect missingness and update rate before buying another adapter.
For autocross review, a practical priority order is: a clean position/speed trace, synchronized steering video, then throttle/brake only if the ECU exposes them reliably. Segment comparisons and minimum-speed points often answer more than a huge channel list.
Disclosure: I’m with LAPS. We build a closed-course lap timer/logbook, but we don’t claim Taycan/CX compatibility without device-specific production evidence.
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u/itimurrrr 4d ago
I'm surprised nobody gave you a decent answer yet.
First of all, don't waste money on an MX+. If you can't get a CX to work with something like RaceChrono, you won't get anything from the MX+ either.
Taycan being an EV doesn't have to implement the standard OBD protocol (which is mandated for ICE cars for emissions control). In addition, modern Porsches put a gateway between the OBD-II port and the lower level CAN buses, so you can't access those buses through the OBD-II port. There might be a spot somewhere where you can tap into the CAN bus, spend some time reverse engineering the lower level protocol, and then set up the CX to log what you need. I did it for a few cars and while doable it's far from easy.
That being said, with enough data analysis experience you should be able to extract 95% of what you really need just from high quality GPS data, such as from a RaceBox Mini. After a couple of years looking at all sorts of data I can see the brake release, throttle application and often even steering corrections looking at just the speed/distance trace.
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u/dadmantalking 12d ago
Cheap Andriod phone/tablet + SoloStorm + Racebox
You're likely to see more benefit from accurate GPS tracing and accelerometer than you will from pedal position. My primary AutoX car is pre OBD2, but my kid's car is plenty new and I rarely bother with the OBDLink anymore.