This is not exactly what it looks like back at the ranch when I head out on track today. But as most of you know, I subscribe to the philosophy that it is difficult to improve if you don't measure. For most of the amateur events I do, rudimentary timing is often available which, for the most part, is plenty good. It was far more than I needed at the outset since, in retrospect, I was a terrible driver. And I'm still no great shakes, I come to realize. But getting better is the goal and having a way to measure progress is important to me. So here is part 1 in a greater investigation of the measurement tools, otherwise known as telemetry in racing circles, that a fiscally conservative person like me has looked at. I say fiscally conservative because there are tools that are as cheap as free and others that cost tens of thousands of dollars. Without a multi-million dollar F1 contract in hand, I try to tend toward the free end of the equation and see how far I can get before I plunk down more money. Yes, it's for the children. So let's take a look. (Photo from motoward.com)
As most of you know, I've been a fan of the iPhone app TrackAddict HD for some time. Harry's LapTimer is another one I have and can see value in. But TrackAddict is so much easier to configure and use on the fly that I find myself always going back to it. I'm always a bigger fan of thinking about driving than thinking about hitting buttons and setting up software. My pit crew should be taking care of the buttons, but they don't exist. So I want things to be simple, but usable. So far TrackAddict is my tool of choice. For today's initial look, it's not really about the tool, though. The ugly thing that I've found with all of these tools lately is that the data is sometimes not usable. Suprised? Probably not as much as I was after investing lots of time capturing it. So why and how did this happen?
Here's how I'm setting up: I've got the app on my phone. The phone has GPS built in. I've got an OBDII wifi device to send data from my car's onboard diagnostics port to my phone. Pretty fancy eh? I thought so. But what I hadn't counted on was how often all this lovely, juicy data gets sent to my phone. Why would it matter? At first it really didn't because all I wanted was lap times. That's pretty simple stuff and my phone can at least time things fairly accurately - computers are good for something, right? But then I asked for more.
I started to want to know my cornering speeds. Here he goes, now. Yes, I wanted to know how fast I was going around corners. Could I go faster around some? Would my time improve by going a bit slower in others? So many questions. And I had all this great data to use to find out!! Or did I?
As I dug into my numerous CSV files of data after my runs, I produced copious graphs and charts and tried to visualize my velocities over time, and other highly scientifical things. And I quickly found out...that my data resolution was absolute crap. The line chart of my speed looked like a step function!! The resolution was terrible. In the short span that it took for me to get around most corners, my speed value only updated maybe one and often not at all. I was flummoxed.
So I mulled and stewed and Googled. And then it came to me that people smarter than me already knew that OBDII refresh rates are abysmal. Like maybe once per second (1Hz, to be all fancy). I was expecting at least ten times a second or so. These computers have nothing better to do than send data around, right? In one second at 50mph in a car, I've gone 73 feet - pretty much all the way through the corner. At 60, I'll have gone 88 feet. Yep, corner done and no data change. Frustrating.
But wait, the app is hooked to GPS and can use fancy satellite-provided coordinates and calculate my speed, right? There is a backup plan! We are saved! But wait, how often does an iPhone connect to the heavens? Not as often as you'd hope. Theoretically, its about 10Hz or ten times per second. But the reality I'm seeing is that its about the same 1Hz as my shoddy OBDII data! Here's what that looks like in a chart.
You've got speed on the Y axis and you can see that over 32 seconds (723 sampling points in my spreadsheet but far fewer unique data points in reality), the data is not very fine. I've got both the GPS-based speed and the OBDII-based speed here for comparison. GPS is in blue.
I wasn't going to be able to speed up the OBDII refresh rate on the cheap. The next model year (2008) of my car supposed has a higher refresh rate. Not cheap to make that switch. So I looked next at GPS. I learned that an external GPS unit will, in fact, allow for a higher refresh rate - 60Hz in theory, but probably less than that in reality. In fact, the real refresh rate I'm seeing is about every 2/10ths of a second on average so about 5Hz. Still far better than 1.
So how do things look when the refresh rate increases about five times? Take a look:
For fun, I kept the OBDII speed in there (red line) as well so you can see just how choppy and poor the built-in wiring from the car is! I'd have to say that getting any usable data via the OBDII port just isn't really going to happen. Something like the rev counter (RPMs), where you'd expect that data to be basically a continuous curve again just looks like steps because of the poor refresh rate. It's hard to describe my moment of dejection and defeat to know I had all this data on hand...and none of it would really yield any wisdom.
But with the external GPS, I suddenly have at least a snowball's chance of getting some decent, usable info. The painful part now is getting all these external devices charged, strapped down in the car, connected to my phone (reliably), and working. I am heartened, I suppose, by the fact that at every other F1 race, some team or other gets on the radio to tell the driver that they have no telemetry. I'm just like, "oh, yeah. I know exactly how you feel right now guys. Flying blind again." Except they paid millions for their systems. And I strung together a phone an a cheap OBDII dongle and a cheap external GPS. So it feels a lot less bungled when my system is on the fritz, I must say.
But this past weekend, the work of setting up the cameras (1 GoPro and 2 similar knockoffs), phone (whose holder has decided not to hold on my windshield anymore and falls off mid-corner at times, lucky without dropping my phone onto the track so far...), external GPS (which usually runs out of battery just about when I was going quick and needed it to work), and the OBDII dongle (so damn flaky as to when TrackAddict software decides it wants to be able to communicate with it. Really maddening at times, but turns out that OBDII is lame anyway!) was just so daunting that I bailed on it nearly completely. I did find that TrackAddict's speed logging was useful for my 4-cone-slalom exercise so I could see if my speeds were going down during each run and by how much. Hard to figure out the accuracy of it sitting in my car, but it made me feel good to at least have some reference point since looking at the speedo while trying to drive would have been very difficult.
For the remainder of the day, I just drove au natural (fully clothed but with no "technical support" or logging). It felt good as I got to really talk to folks from the crowd, got to enjoy the people - the main thing that makes autocross into an enjoyable pastime really. And I thought harder about traction and feeling the tires and the steering. All the real things that make a difference.
What I've learned through trial and error (lots of errors) in my person journey to be a better driver and have fun with cars is that if you really enjoy something, improvement is certainly of importance, but keeping it at the level that maintains your enjoyment is critical. Too much is too much. Sometimes we overthink and overdo it a bit. I've heard others say it before, but I think it really is about the "people and the cars" so much more than just the cars. It sounds like a basic thing, but it wasn't until I spent enough time to really know the people that I learned this lesson. And I'm certainly still learning. And having fun.