Any racechrono pro experts in the house?

Just read the most recent mag article on data acq. So now I want to buy one naturally. I've lightly used both track addict and harry's lap timer on my phones long ago, and even went so far as to buy a dual xgps unit for improved gps response a year or two ago. Unfortunately, I never liked the need to use the phone for multiple purposes, and I had difficulty with storage space and consistently recording stuff.

Now I have a phone that I am no longer using as a phone, that I think I could dedicate to being a data logger all in one unit.

So a few questions for the folks who use racechrono:

1. Does it need cell service to function? i.e. can I use it on a phone that I'm not paying monthly service for?

2. Does it work well for autox? 

3. How does racechrono pro ($20) used on android with an external gps unit - and possibly an external bluetooth obdII adapter - compare to something like the aim solo2 with a corded connection to my ECU ($500ish)?

I use RaceChrono Pro on my iPhone and previously on my Galaxy.  Both work great on their own but I use an external Garmin GLO GPS unit for increased accuracy.  For autocross I just use the phone to set my trap markers during the course walk and then use the Garmin when I'm making my runs.  It works extremely well.

For your questions:

1. Not sure but I'd lean toward no.  You're paying for the data.  With no data I doubt the GPS function of the phone would work but I may be wrong.  If you went with the Garmin GLO this would no longer be an issue.

2.  Yes, very well.  I have multiple videos of Autox on my Youtube page or in my build thread here if you want to see it in action.  Username Restless Performance.

3.  My car doesn't have an OBD2 port so I can't really provide an answer.

As long as you have an external gps receiver you don't need a cell connection. I used it on a WiFi only tablet for a long time. I'd occasionally run into an issue where if it had been a long time or the app had been updated or something I'd have to briefly connect it to my phone's wifi to verify the license. Fwiw last year I switched to using it on my phone and it's so much better than having to lug a second device around, even if the screen is tiny.

It works just fine for autocross, that's my primary use. Pro solo isn't great but it's doable.

I've never used an aim so I can't really give a direct comparison. But it looks like it runs at 10hz, and any decent external receiver will also be at least 10hz, so at least theoretically the data they produce should be pretty similar. I'm not necessarily saying that's absolutely true, but it should be at least close. If you're looking for lap times I'd say there's no real difference. If you're looking for more in depth analysis, the aim is probably better. Enough to offset the cost difference? Probably not, but that's really up to the user to decide.

This is good news, thank you for the help so far. For $20, I think it's worth a shot. Another question for data pros - do you find the OBDII data helpful? like seeing the TPS trace or RPM or something? Or is GPS and accelerometer (and time) data good enough?

It does seem like racechrono pro at least on android may be able to add some additional lines of data in even outside of what OBDII gets you. I'm thinking some tire pressure data would be cool to track?

Robbie (Forum Supporter) said:

This is good news, thank you for the help so far. For $20, I think it's worth a shot. Another question for data pros - do you find the OBDII data helpful? like seeing the TPS trace or RPM or something? Or is GPS and accelerometer (and time) data good enough?

It does seem like racechrono pro at least on android may be able to add some additional lines of data in even outside of what OBDII gets you. I'm thinking some tire pressure data would be cool to track?

It depends on your level and what you're trying to get out of it. OBDII info is helpful if you have gas/brake. GPS you can *infer* gas brake from longitudinal G. Having a Cell signal is nice when setting up course markers so you can SEE the map, but isn't strictly necessary. Having used Harry's lap timer and Track Attack from HP tuners, I've found RaceChrono to work the best for me.

It works great for Autocross, Set the gates on your course walk, and I just start the session and let it run the whole time (same thing for a track session), though I manually start the GoPro (through the app). Track attack you have to click start to every run and I've never gotten it to work right.

I had trouble with my Garmin GLO (battery/charging) but have had great success with the QSTARS 10Hz antenna. It took a little fiddling but I've got the GoPro connection down as well, which makes overlayed exports super easy. You do have to download the video from the camera to the phone to do the overlay and analysis though.

AIM solo is all a self-contained unit (unless you add a SmartyCam), so no fiddling with an antenna, and has a more powerful analysis software that most race teams and people who know use, but requires a laptop to really dig into it. RaceChrono, Solostorm, ApexPro, etc you can look at on your phone between runs

Throttle trace is nice, and brake if your car is able to output it. Anything beyond that is pretty unnecessary. Maybe something like iat/coolant temp if you're running aftermarket forced induction or something like that. That said I've exclusively competed in obd2 cars for several years now and have yet to get around to setting up the obd reader, and there's only been a couple of times I've really regretted that.

For your 1st question, the wifi and gps will work on phones with no carrier/sim in them in 99.9% of the cases that I'm aware of. So things like Harry's lap timer, etc work fine still. I usually tether my old "no service phone" to my current phone (some phones can turn themselves into wifi hotspots) if I need to update something at the track, etc. The gps receivers built into most phones aren't very granular, that's why people use external gps receivers with them usually.

Just thinking about this some more - I think a lot of people think their "GPS doesn't work" on phones without cell-service because they check google/apple maps and it doesn't show up when they're not connected to wifi. This is usually related to what data is cached on the device, not the gps not working - most map applications on phones (unlike your standalone gps navigation units in cars/etc) don't have all the map data stored on the device, just small pieces of it.

Most cellphones use several "tiers" of location services. They use the cellular towers to do a very rough triangulation (for some application, this is all they need and it's much more power efficient than listening to gps) - this is why when you open some map apps they'll be kind of close to your location and then slowly get more accurate. Not having that rough triangulation will make it much slower to get a good gps fix.

A device with a real GPS receiver (like most modern phones) are an antenna receiving a globally broadcast signal. i.e. the data being sent over the air is more similar to AM/FM radio than to 4g/5g cell service, etc - hence it still works with no carrier - you just need an antenna and processor able to interpret it.

So that's a bunch of info you didn't want/need filled with many corse generalizations. But I suppose you get what you pay for! ;)