We used an $8 cell phone case from Amazon and a few zip ties to hold our cellphone to the dashboard.

There are all sorts of gizmos companies want to sell to racecar drivers to help with data acquisition. Some are extremely pricey and require an engineer to understand half the data that comes out of them. The average weekend racer wants to know one thing: Was my last lap that felt fast actually faster? A lap timer is a great tool for this question. Some older systems require boxes with signals at the start/finish line, and they have batteries that need to be charged and they often get forgotten after a session and left behind at the track. Other pricey systems need connections with transponder signals. All of them cost more money than most of us want to spend.

The good news is most of us are walking around with a sophisticated data acquisition system in our pockets: a cell phone. Granted, most of us only use these things to play Angry Birds while sitting on the toilet, but they can be used as an incredibly accurate lap timer. Yes, there is an app for that.

Harry’s Lap Timer costs $19.99, which, for most of us, will be the most expensive app we will ever buy for our phones. However, compare that cost to a Racepak IQ3 data logger and you will be happy to have Harry charge your debit card $19.99. This dude, Harry, is a German engineer who loves the Nuremburgring, the kind of guy you want designing a racing app.

This data screen shows the date, time, lap time, track, vehicle, number of laps for the session, etc. It also shows a map of the course. You can add your own notes regarding setup, weather etc. for your own database. Impressive for $19.99 and a couple of zip ties.
This data screen shows the date, time, lap time, track, vehicle, number of laps for the session, etc. It also shows a map of the course. You can add your own notes regarding setup, weather etc. for your own database. Impressive for $19.99 and a couple of zip ties.

Once Harry’s app is loaded on your phone, you can see the gamut of what is possible for data acquisition and video overlay. We didn’t play with the video overlay because our goal wasn’t to create YouTube videos with track maps and vehicle speed that nobody is going to watch. Our goal was to know what our lap time was after each lap. Was it better to downshift into second in one corner or not? We needed answers!

On this screen you can see the lap chart laid out with the track configuration at the top of the screen. At the end of a session, I can scroll through and see how my different laps compared with one another.
On this screen you can see the lap chart laid out with the track configuration at the top of the screen. At the end of a session, I can scroll through and see how my different laps compared with one another.

The next step was to install the phone in the car in a location where I could see the lap time. The cool feature on Harry’s Lap Timer is even though it is a live feed of time, like a stop watch, it freezes the lap time after you cross start/finish so you have a moment to take a look at it, see that you went slower and then curse in your helmet. After about 10 seconds, it goes back to the live feed of timing for the subsequent lap. Obviously it is important to have the phone located where you can see the screen.

Harry’s Lap Timer is easy to use at the track because all you do is tell it what track you are at and then hit the “Ready for Driving” button. The timer won’t start until you cross the Start/Finish line based on GPS coordinates. You don’t need to hit a button at Start/Finish or mess with it during the race. Just set it up in the paddock before you get in the driver’s seat and then go fast.
Harry’s Lap Timer is easy to use at the track because all you do is tell it what track you are at and then hit the “Ready for Driving” button. The timer won’t start until you cross the Start/Finish line based on GPS coordinates. You don’t need to hit a button at Start/Finish or mess with it during the race. Just set it up in the paddock before you get in the driver’s seat and then go fast.

In timing mode, the screen uses a large font to make it easy to see the lap times. We placed the phone near the glove box so the phone could collect data from GPS satellites through the windshield. To hold it in place, we used a cheap cell phone case and some zip ties. Simple as that.

Using some zip ties and a cheap phone case, we used some existing holes where the glove box used to be and tied the case to the dashboard. We picked a spot where I could see the lap times as I crossed start/finish.
Using some zip ties and a cheap phone case, we used some existing holes where the glove box used to be and tied the case to the dashboard. We picked a spot where I could see the lap times as I crossed start/finish.

We went to Buttonwillow Raceway Park to test our new toy and found to our satisfaction that Buttonwillow was a track the app recognized. All we had to do was choose the track configuration on the phone’s menu, and then click “Ready for Driving.” The app switched to the large number timing screen and waited for us to drive past Start/Finish on the first lap, which it recognized from GPS coordinates. Then all we had to do was drive fast.

As I came across Start/Finish on my second lap, the lap time froze long enough for me to see it on my phone and for me to decide what kind of adjustments to make on the next lap — like build a new motor. After the session was over, and I was out of the car, I walked around to the passenger side and told the app my session was complete. Then I could scroll through all sorts of data: lap times, miles per hour, acceleration, deceleration, lateral g’s, consistency, you name it. I took the phone over to the posted qualifying times from the track’s transponder loop to see the difference between Harry’s GPS data and the hardline AMB transponder signals. Harry’s Lap Timer said that 2:09.02 was my best lap. My official qualifying time from AMB was 2:09.054. Only three hundredths of a second apart, pretty impressive for $20.

What I like about this chart is that it’s a quick way to gauge consistency. Were all of my laps about the same pace? Shamefully, no. Obviously traffic and yellow flags can affect this, but I like to see how consistent I am because consistency wins races.
What I like about this chart is that it’s a quick way to gauge consistency. Were all of my laps about the same pace? Shamefully, no. Obviously traffic and yellow flags can affect this, but I like to see how consistent I am because consistency wins races.

Long story short, Harry’s Lap Timer works. It is easy to use, which is nice, since you have enough stuff at the racetrack to worry about. There are a lot of other options with the app that we didn’t bother to explore (autocross use, video overlay, etc.). My only concern with the app was that somebody might call me in the middle of a race. “Hi, this is Rob. I can’t come to the phone right now because I’m either crashing or winning a race. Leave a message and I’ll call you back either from the hospital or the winner’s circle!”

This screen shows an image of the track configuration behind the mile per hour chart. Here you can see if changes in aero between sessions affect your top speed. This is great data when playing with rear wing adjustments. It also is important to look at your lowest speeds, too.
This screen shows an image of the track configuration behind the mile per hour chart. Here you can see if changes in aero between sessions affect your top speed. This is great data when playing with rear wing adjustments. It also is important to look at your lowest speeds, too.

To read more from Rob Krider or to contact him go to www.robkrider.com.

On the timing screen, the lap times are in a huge font, which is perfect for seeing what your lap time is as you are thrashing around the course. You won’t be able to see the tenths or hundredths of a second in this mode, but that data can be viewed later when you aren’t racing.
On the timing screen, the lap times are in a huge font, which is perfect for seeing what your lap time is as you are thrashing around the course. You won’t be able to see the tenths or hundredths of a second in this mode, but that data can be viewed later when you aren’t racing.
This RAM mount is great for holding your cell phone in your tow rig to help with GPS directions to a new track, but we found that the portion that holds the phone may not be industrial enough for the undulations on a racecourse. With some zip ties this could work, but you definitely want to ensure that phone doesn’t come loose in the racecar.
This RAM mount is great for holding your cell phone in your tow rig to help with GPS directions to a new track, but we found that the portion that holds the phone may not be industrial enough for the undulations on a racecourse. With some zip ties this could work, but you definitely want to ensure that phone doesn’t come loose in the racecar.
This track map is cool because it can show your acceleration (green) and deceleration (yellow) as well as lateral g’s with the thickness of the line all on the track map itself. The interesting part is in Riverside corner — where I know I was on the gas the entire time based on video data and my huge balls — I was still slowing down due to the banking and the radius of the long banked corner. This is something I never would have known without looking at this map with data.
This track map is cool because it can show your acceleration (green) and deceleration (yellow) as well as lateral g’s with the thickness of the line all on the track map itself. The interesting part is in Riverside corner — where I know I was on the gas the entire time based on video data and my huge balls — I was still slowing down due to the banking and the radius of the long banked corner. This is something I never would have known without looking at this map with data.
Zip ties are your friends and we looped some laterally around our phone, with another set vertically behind the phone (out of view in this photo) to ensure this phone did not come loose in the car.
Zip ties are your friends and we looped some laterally around our phone, with another set vertically behind the phone (out of view in this photo) to ensure this phone did not come loose in the car.
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Image courtesy of Rob Krider