Beyond Thompson

At the last Lemons race at Thompson, I only got in 6 laps of practice. However, the AiM Solo was running then and during the race, so I got to do a little comparative analysis afterwards. In the graph below, the red line is my fastest practice lap while the blue line is the fastest race lap on Sunday. Click on the image to open it up in a larger window and then write down at least 3 things you notice that’s different about the two traces.

  1. OK, so the most obvious thing is that the drive down the main straight was very different. I had an extra 200+ lbs of passenger and gear in the car and was driving in 4th gear. There may also have been traffic.
  2. The second thing you probably noticed was the very low speed in T2. I was experimenting with the brakes seeing how good they were, so my braking point was very late and this caused me to botch the corner. No big deal, this is what practice laps are for. I had never driven the car before and I needed to experiment. I tried different lines and gears nearly every lap.
  3. The thing I want you to notice next is that all the red lines are shifted left relative to the blue lines. The braking points are earlier and the acceleration points are earlier.
  4. Because my acceleration is earlier, I tend to have higher speeds on the way to the next corner.
  5. The most important area of the track is the 9-10 combination that sets up the main straight (6000-7000 ft). I take this as a single descending radius corner rather than two corners.
  6. While the 7-8 carousel (5000-5500 ft) isn’t nearly as important, I have a very different line compared to everyone else on the team (who all take a line similar to the blue one).

We could go through each corner talking about the trade-offs of taking different lines. But the differences in the red and blue lines aren’t really about Thompson. We can summarize all the specific differences with two general strategies, which I’ll describe below.

Backing up the corner

In point #3 above, I noted that my driving style involves braking earlier and accelerating earlier. This is called “backing up the corner”. The earlier you can get the car pointed to the exit, the earlier you can get to full throttle. Getting the car rotated early is usually accomplished by trail-braking deep into the corner so that the steering and braking inputs overlap quite a bit. This has the effect of swinging the rear of the car around, and you may have to make a steering correction to prevent the car from oversteering into a spin. There are risks involved when driving with this style. That said, no matter how hard I tried, I couldn’t get the car to rotate. It was set up with a lot of understeer. While I could get on throttle early, the car was leaned over quite a bit, and the open diff caused the inside front tire to search for traction. But even without getting the rotation I wanted, you can see from the telemetry graphs that there are gains to backing up the corner.

Connecting combinations

There’s only one combination corner at Thompson: 9-10. The blue driver “sees” this as 2 corners with a small straight between them. You can see this as the hump in the speed graph. The red driver (me) sees this as one long corner. Why? It’s the most important corner of the track and my goal is to optimize the position, angle, and speed of the nadir (slowest part of the corner). So I focus all my attention on getting to the nadir with the best combination of grip and speed that I can, which means throwing away the first corner. By slowing down early and keeping the suspension quiet, I optimize grip. If I speed up too much, or turn too much, I’ll upset the car and lose grip. This costs me some time at the start of the corner, which you can see at 6100 ft. But the investment pays off as from then on I’m gaining time.

Summarizing

Next time you’re on track, try making a conscious effort to get your shit (braking, turning) done earlier. Stop optimizing the straight you’re on and start optimizing the straight coming up. Also try to get your connected corners more connected. Think about how the first corner affects the second. Try some different lines to see what works and what doesn’t. Make sure to bring a data acquisition device. Not only will it help you sort things out later, it also makes the downtime between track sessions a lot more interesting.

2 thoughts on “Beyond Thompson

  1. Adding on to #3 the slope of your braking is slightly steeper on several corners. The blue driver compounds his issue of dealing with understeer by braking later but then also not slowing down quick enough to stabilize for the next corner. This translates into a ‘U’ shaped valley – my guess the blue driver is on maintenance for quite some time past the apex before he can pick up the throttle.

    What happened at the 4000 mark for your lap (red)? Traffic/trying something new or is that how it was consistently?

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    1. Right on. Those are U-shaped traces in slow corners. That’s a no-no.

      I looked at the other laps I did and none of them looked weird at 4000. Sometimes there are little spikes in the data.

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