by Dana Comolli
In my previous articles, I’ve discussed how data use can inform and improve your driving. To date, I’ve focused on three data channels: Speed, Lateral Acceleration, and Longitudinal Acceleration, all of which are accessible without having to port into your car’s controller area network (the “CAN bus”).
We now consider Math channels, which can be used to derive new information from existing channels. More specifically, we’ll consider how to tell when and where you’re on the accelerator, slowing, turning, or coasting.
Once again I’ll be using AIM’s SoloDL and their Race Studio Analysis software, though any similar device and application will work. The data will be derived from the same two laps at Blackhawk Oktoberfest 2019 that I used for the previous articles.
Math channels are measurements you define that use other channels as input (data from the car or other math channels) that you reprocess to create new information. Figure 1 shows the definition of a Math channel called “Turning” which is set to 1 when the car is turning and 0 when it is not. This is derived by looking at the GPS Lateral Acceleration channel: if the absolute value is greater than or equal than 0.20g it sets the value to 1, indicating a turn, otherwise it is set to 0. I’ve highlighted the formula portion of the definition for clarity.
Using the GPS Longitudinal Acceleration channel allows me to define a Math channel that indicates when the car is Accelerating (a value greater than or equal to 0.05g) and one that indicates when it’s Slowing (a value less than or equal to -0.05g). By combining these newly defined Math channels, the result is a read-out that indicates when the car is “coasting,” i.e., a state where the car is not slowing, not accelerating, and not turning. The formulas are shown in Figure 2.
Now that these channels have been defined, they can be applied to graphs and track maps to gain a better understanding of your actual inputs as a driver. Figure 3 shows these and the underlying measures on a single chart of one lap.
Using a track map augmented with the data values is where this really becomes instructive. There are three places where I was coasting (labeled 1, 2, and 3). Figure 4 shows a track map that shows where they occurred. Location 1 shows I was a little slow getting to the brake going into turn 6 and location 2 shows trepidation going into the kink. This was the last lap of the session and location 3 is where the cool-down lap started.
Analyzing this data, you can compare laps to look for clues as to why one lap was faster than another. Figure 5 shows the same two laps I’ve used in this series (the outer lap is the faster of the two); the map is configured to highlight slowing in Blue and accelerating in Green.
You can see as we go into Turn 1, the slower lap over-slowed and had to get back on the throttle. The slower lap also slowed all the way through turn two and again over-slowed into Turn 3. In contrast, the in the faster lap, I trail-braked all the way to the apex and then was back on the gas. The speed trace in Figure 6 is another view of this comparison.
In addition, you can also see where I lifted near the end of Turn 3 in order to get some rotation, which permits earlier acceleration through the esses. The speed trace in Figure 7 confirms this analysis (the circled area of the graph is the lift).
Turn 6 shows better use of the brake going into the turn, combined with a lift near the second apex during the faster lap. The slower lap again over-slowed into the turn and again mid corner, resulting in a speed deficit all the way down the back straight. Finally, the faster lap also braked later into Turn 7 and accelerated earlier onto the front straight. The speed trace in Figure 8 backs this up.
Turn 6 shows better use of the brake going into the turn, combined with a lift near the second apex during the faster lap. The slower lap again over-slowed into the turn and again mid corner, resulting in a speed deficit all the way down the back straight. Finally, the faster lap also braked later into Turn 7 and accelerated earlier onto the front straight. The speed trace in Figure 8 backs this up.
