Using data to understand where you got faster and why

In the wake of running NASA Utah Round 1 at my home track of Utah Motorsports Campus’s Outer Loop, I took a look at my fastest lap and compared it to last October — the inaugural race with the new-to-me NB Spec Miata.

I was faster. A LOT faster.

3.1 seconds faster, to be precise.

Where did all of that time come from?

I made significant setup changes to my car based on my notes from last year. I knew which corners I was losing-out on to my competitors in and had a theory that I needed more negative camber.

That theory proved well-founded. The car felt stable and capable at higher speeds. I felt the ability to “lean” on the car into corners at higher speeds — what an amazing feeling!

How Much Faster Did I Go? Where?

Using a data system, the most-basic measure of performance is our speed/distance graph. It shows us squiggly lines that tell us how fast we are going at any point on a race track.

When comparing two laps, we can begin our investigation in the corners:

• What are our minimum corner speeds?
• What are our maximum straightaway speeds?

Looking at my own data, I found improvements across the board in the Minimum Speed category:

• T1: 5mph
• T2: 2mph
• T3: 5mph
• T5: 4mph
• T6: 3mph
• T8: 2 mph
• T11: 1.5mph
• T13: 4.8mph
• T14: 2mph
• T15: 2mph

Seeing speed improvements above the 2mph mark is outstanding (and just goes to show how much opportunity I was leaving on the table!).

That said, let’s zoom in on T11 (Tooele Turn), which had the lowest marginal improvement.

What Is 1mph Worth?

In the right corner — a lot. Looking at the data (fast lap in blue, slower lap in red), I was able to determine the impact of carrying more speed.

Tooele Turn is a deceptively high-speed corner that feeds onto the 2nd longest straightway on the track. My minimum speed went up from 66.8mph to 68.2mph (details matter — and I love GPS speed logging!)

Looking at all other data, the only thing that improved was my cornering speed — my throttle lift and application points are nearly identical (so it’s not like I was able to get to throttle earlier or go deeper into the corner).

The gain: 0.35 seconds

That 1.4mph resulted in 10% of my overall lap time improvement!

Put that marginal gain with a lot of other, much larger marginal gains and… 3.1 seconds starts to add up pretty quickly!

Where I Gained the Least Amount of Time (kind of)

Short answer: the straightaways.

We are all experts at mashing the skinny pedal down and, fortunately for me, my capabilities in last October were good-enough that my corner exit execution was apparently pretty decent.

Once we straighten the wheel and put the power down, our cars get up-to-speed the same way every time (mechanical improvements/issues notwithstanding).

So, if we are 1mph faster in a corner, then we get to add that 1mph to every second we’re going down the straightaway. The longer the straightaway — the bigger the payoff.

That said, those are the “easy gains”. Focusing on getting the car to be “happy” in corners earned me those corner-exit miles-per-hour.

Digging Deeper

To further validate that my setup made the difference, I looked at a handy function in AiM: G-Sum

G-Sum adds up our latitudinal (turning left/right) and longitudinal (acceleration/braking) G-Forces and adds them together.

Samir, founder of Your Data Driven, provides a great overview of this function, which I will not try to recreate.

In this example, my blue lap was faster – I could see this in the higher speed trace across the entire corner, but looking at G-Sum, I can also see that I do a better job of transitioning cornering force into acceleration force. My blue lap has a higher and smoother arc as compared to my red lap in this part of the corner.

That said, the TL;DR is this:

Smoother G-sum curves are better. The smoother you transition from braking to turning, then accelerating, the more speed you’re carrying overall in the corner.

I saw a consistent theme where my G-Sum was always a bit higher, a bit smoother in my faster lap. This means I’m able to carry more speed into the corners (cha-ching!) and with fewer “bobbles”. The setup is working!

Now… What Can I Do To Go Even Faster?

Looking at a couple of key corners, I’m noticing some dips in what should be a nice, smooth arc. Especially when comparing to my brother where he is faster in certain corners.

I’m Blue, Blake is Red. I’m discounting the frequent variation in his arc due to a different sampling rate between our AiM dashboards – haven’t sorted-out how to smooth his arc, yet. Blake is significantly faster in a few corners, so I know I have things I can learn from his data.

T1:

T5:

T1 has a plateau as I build my gSum to it’s maximum level for the corner and T5 has a valley. Comparing this to Blake, I’m just a little slow in the mid-corner phase of T1 and corner-entry phase of T5.

This means that I am not trail-braking as efficiently as I could! I’m leaving usable traction “on the table” as I enter these corners. It may also indicate a late turn-in for T1.

To approach improving this, my plan is to gradually attempt to carry a bit more speed into the corner on entry, possibly a bit later in the corner. This will involve trying braking later, braking lighter, and adjusting my turn-in points and how quickly I “wind” the wheel.

Want Your Data Analyzed?

If you’re running an AiM unit and are wondering where your greatest opportunities lie, reach out! Send me a note at greg@lvry.co