I modelled the track using my GPS data from CSCS #4 last year and modelled my car using some basic estimations and information available from NASIOC and Wikipedia.
I had to make some guesses for values such as frontal area, downforce co-efficient, etc. but after looking at some of the example vehicles they had of passenger cars (M3, Miata, Corvette, R8, 911) I noticed they were all in the same ballpark area. Playing with these values only made thousandths of a difference to the lap time anyway.
Dyno chart I took from a typical Stage 2 chart I found on NASIOC. Since my car was road tuned I never dyno'ed my car. All the Stage 2 charts look similar anyway.
Tire Data, in particular Longitudinal and Lateral Friction, played such a significant role in determining lap time that even changing these by 0.1 had an impact of 2-3 seconds on the overall lap time. I settled for a value of "1" which was somewhere between the street car Civic they modelled (0.9) and the M3/Corvette (1.2).
Final estimated lap time, assuming The Stig as the driver, was 1:20.61. My personal best is 1:22.93. And I still have a lot of work to do with my line, especially through T1. So this does seem to be somewhat realistic.
Digging deeper into the results is where things fall apart a little. Looking at the track speed graph is where I noticed things to be really off. The maximum speed (185 kph) is way faster than actual (161 kph) and the minimum speed (47 kph) is way slower (61 kph). See video for reference:
Despite these drawbacks, I found the program to be useful in comparing changes made to a single vehicle. For example, adding a VF39 and USDM 6MT would shave off approx. 1 second. And adding just a 6MT without upgrading the turbo would make the car 0.15s slower due to the added weight of the tranny. An extra 100-150whp would net me around 2.5 to 3 seconds in lap time. All assuming I stay with the same tires (since the tire modelling is kinda messed).
Here are the predicted lap times for some hypothetical setups:
- 1:17.55 - Borg Warner EFR 7163, JDM 6MT
- 1:18.02 - Borg Warner EFR 6758, JDM 6MT
- 1:18.26 - Blouch Dom 1.5XT-R, JDM 6MT
- 1:19.13 - Blouch 18G-XT, JDM 6MT
- 1:19.71 - VF39 Stage 2, USDM 6MT
- 1:20.61 - Stage 2 (Current Setup)
- 1:20.76 - Stage 2, JDM 6MT
I only spent a few hours playing around with the program. With more accurate real world measurements and some more time playing around with the modelling, I think this could be a very useful tool for anyone looking to maximize their setup. You just need to be aware of what you're playing with so that it's not garbage-in, garbage-out.
In summary, for a free program, Optimum Lap is awesome!