Endurance Racing Simulations

For endurance racing it’s important to know the amount of energy used per lap, because that determines how far you can go on a tank. You can get this data from OptimumLap simulations. Again, this isn’t expected to be exact, it’s for comparison sake. From the energy used, you can determine the length of each driver’s stint, as well as how many laps they can complete in each stint. This can be very important for pit strategy, especially in longer races. 

The configurations I used for the simulations follow this key. Note that the “B” group has less aero: it uses an airdam, but not a splitter, and no wing.

  • 1a – Open top, wing, airdam, splitter
  • 2a – Chop top, wing, airdam, splitter
  • 2b – Chop Top, no wing, airdam, no splitter
  • 3a – OEM hard top, wing, airdam, splitter
  • 3b – OEM hard top, no wing, airdam, no splitter
  • 4a – Fastback, wing, airdam, splitter
  • 4b – Fastback, no wing, airdam, no splitter

In the table below, the Energy value in the table comes straight from Optimum Lap, and I’ve simply taken a value of 16,500 energy units divided by the energy used to get the number of hours per tank. The Miatas I’ve raced have burned about 7 gallons per hour, so these values aren’t far off.

ConfigClCdWGI LapEnergyHours per tankPit stopsLaps in 8 hours
1a-0.430.43144.029087.531.824174.98
2a-0.530.45144.049141.081.814174.95
2b0.310.48147.749183.121.804170.57
3a-1.010.48142.969223.371.794176.27
3b0.50.45148.179078.141.824170.07
4a-1.20.41141.069031.231.834178.65
4b0.350.38146.518911.281.853174.05

Take a look at the first two, this is the open top vs Chop Top, and it’s interesting that they turn almost exactly the same number of laps. The OEM hard top beats those by a lap and change.

But the fastback configuration 4a is the clear winner here, turning 178 laps, two more than the OEM hardtop with the same aero. Make this into a 24 hour race and the fastback wins by seven laps. Notice the Energy column, the fastback with wing is not only turning the fastest laps, but it’s using less gas than any other configuration, save the fastback without the wing.

In the non-aero B-group, the fastback (4b) wins by three laps over its wingless brothers. This is partially because the fastback can take one less pit stop. If I re-run the data with a larger gas tank so that all configurations have the same number of pit stops, then the fastback wins by only two laps. 

But once you add a wing, the race is over. In fact the worst combination with a wing (open top) beats the best performing top without a wing (fastback) by a full lap, even though the fastback does one less pit stop.

If you want to check my math, I have a spreadsheet with these values, and for simplicity, I’ve removed a lot of the variables in this table. You have to keep track of things like yellow flags and time taken for each pit stop, which determines the actual driving time per race. The 8-hour race I’ve simulated uses 420 minutes of racing time instead of 480 minutes. Yellow flags at Watkins Glen take longer, and I’ve also subtracted 5 minutes per pit stop. 

For shits and grins, the eBay wing

Let’s see what happens when we use the airdam, splitter, OEM hardtop (without the vortex generators) and the cheap eBay wing. This is configuration 3c in the table below. Look above and compare.

ConfigClCdWGI LapEnergyHours per tankPit stopsLaps in 8 hours
3c.56.55145.719393.391.764172.95

The eBay wing (3c) loses to every configuration that uses the 9 Lives Racing wing. Yup, even the open top car with a 9LR wing is going to be the hardtop with a cheap wing. However, the eBay wing beats OEM hardtop without a wing (3b) in both a sprint race or an endurance race. So it’s worthwhile running a cheap wing if you have nothing at all.

The biggest difference is the Energy field. Compared to the lowest drag version (4b), the eBay wing uses 5% more gas on every lap. That may or may not be a consequence, depending on how long you’re in the car.

It wouldn’t matter in a sprint race; the eBay wing (3c) would win against the fastback without a wing (4b). But in an endurance race, it would depend on the tank size and driving stint time. If I change the data so that they all take the same number of pit stops, then the eBay wing wins. If I leave the gas tank size as it is, then the fastback without a wing wins.