Sorry for the dramatized title. However, that is exactly what we'll be doing today.
Recently, at Roebling Road Raceway, Carlos Mendez and I got to drive the same car, on the same track, in the same conditions. I had the distinct advantage of being the owner of the car and having driven it in more sessions that day, but Carlos at least got to take the car out twice to gain a little bit of extra familiarity.
We both had to contend with traffic during our laps, but I was surprised that we each achieved a nearly identical lap time and the laps were drastically different.
Before we dive in, let me remind you that I'm a total beginner when it comes to data analysis, but hey, I'm trying to learn! If I get anything wrong here, please feel free to point it out to me.
Carlos and I had laps that were a mere 26 thousandths apart (0.026 seconds), according to the AiM GPS data. However, there was a point in the lap that I was more than 6 tenths ahead of his lap. From the data we can see where I was faster, how our lines differed, and we can hypothesize why (I unfortunately don't have video from Carlos's session).
Carlos is the red line.
I am the blue line.
Note that the segment numbers are AiM defaults, and the corner numbers are off because the straights are counted as a segment. Turns 1 and 2 show up as the blue "2" segment, for instance.
Turns 1 + 2
As we enter turn 1, I brake about 100ft earlier than Carlos, and my braking slope is not as steep as his, meaning he applied the brakes harder than I did. There's a little bit of a curve at the top of my peak that shows I coasted a bit before applying the brakes, a bad habit of mine.
Surprisingly Carlos enters turn 1 tighter and exits turn 2 wider than I do, which is the opposite of what I would have guessed based on how we describe how we take those corners. The video of my lap shows I made a pass going into the braking zone, so starting shallower might have meant I went wider than I normally do through turn 1.
As we settled the car down in between turns 1 and 2, the faster car trades back and forth between us, but the lap time delta does not change dramatically through these two corners. The largest difference was still less than 1/10th of a second.
By the exit of turn 2, we are dead even.
This corner requires a lot of commitment. Our lines were nearly the same through this corner, with myself staying to the left a little bit more on the exit and Carlos braking for turn 4 in the middle of the track.
I was able to stay in the throttle, maintaining 100mph through most of the corner, with a min speed of 98mph and an exit of 102mph.
It looks like Carlos over-slowed the car, entering at 98mph but maintaining about 90mph through the corner, with an exit speed of 99mph. It is very possible that Carlos was trailing another car, or made a pass towards the exit of this corner.
By the exit of turn 3, I am 4.1 tenths (0.419) ahead.
Not dramatically different here, but enough that Carlos earns back about 1.5/10ths (0.150) by braking later and carrying more speed to the apex. Our min speeds are identical at 65.0mph. However, I get back on the throttle earlier and hug the inside through the exit to set up for turn 5, regaining 1/10th back.
By the exit of turn 4, I am 3.6 tenths (0.361) ahead.
This is an interesting corner since we drive a similar arc, but on a different trajectory. I start on the outside, cut inside, then we both end up at the same outer zone where you set up for the second half of the decreasing radius corner. Then I finish the corner back on the inside, setting up for turn 6.
Carlos starts on the inside, trails out towards the outer zone where our lines converge, and then stays tracked out which sets up turn 6 a bit shallower.
The deceleration arc says more than the line does. Carlos brakes earlier and less, and maintains a 9mph higher min speed than I do. I brake larger, sharper, and over-slow the car too much. The video shows that I caught a small slide here, contributing to the scrubbed speed.
Braking later gives me my largest delta advantage at 0.617 seconds, but that is quickly back down to 0.422 again by corner exit.
By the exit of turn 5, I am 4.2 tenths (0.422) ahead.
Turns 6 + 7
This corner is nearly a repeat of turn 5. I brake later and more aggressively than Carlos, causing me to over-slow to the apex of the corner. It costs me almost 2 tenths. I did make a pass entering this corner, but I don't think it compromised what I would normally have done.
Our mid corner lines are about the same, but I am further to the inside in the last 25% of the corner and you can see the delta grow again in my favor.
It looks like Carlos had to lift slightly to make the exit of the corner and the delta increases by more than 2 tenths again. He might have benefitted from a bit more rotation of the car through the apex to better set up the exit.
By the exit of turn 7, I am 5 tenths (0.499) ahead.
Turns 8 + 9
This is where it all goes wrong for me! At corner entry I shed 5-6mph, into the low 90's, while Carlos keeps the speed over 100mph through the corner. My line looks quite wide here, too.
Through the corner and to start/finish you can see my delta advantage totally disappear until I finish the lap 26 thousandths behind.
What went wrong that wiped out a half second advantage going into the last corner? The video shows that I came up on two cars pitting in as I turned into the corner, which was enough to give me pause and prevent me from hitting my normal apex.
Unfortunately we weren't running the GoPro in Carlos's session. In any case, this was just a fun lap comparison, and it was a helpful exercise for me to analyze some data, something that I am very new at.
Bonus: 3-Lap Comparison with my PB
We won't dive into this much, but this is the same two laps from Carlos and I, with the third green lap added in of my personal best from later in the weekend, when I broke the 1:20 barrier finally, getting down to a 1:18.7.
There aren't too many glaring differences in the lap, besides braking deeper in turn 1, and carrying more speed through turn 5 since I didn't slide the car there.
The real gap occurs through turns 8 and 9, where I carry much more speed through the corner, and it pays dividends on the straightaway. Coming into the last corner, I had accumulated a -7/10ths delta, with the remaining half a second advantage came from just the final corner.