Milwaukee Mile_OpenWheelTrack 

Lap speed:
I've set the track type, chassis type, and grip values to realize 2013 IZOD IndyCar speeds from the 2013 race, Fastest Lap: 162.405 mph ( 22.4993 sec). There's no way to allow for the qualifying speed, #25 Marco Andretti (42.8584, 170.515 mph), with the NR2003 (full fuel) limitations.
For the Player, when not hindered by traffic, the average lap speeds should be in the 160-162mph range with some 163mph laps. (Fastest lap: 165.108, Fastest Race lap: 164.579) The fastest ai should run 160.8-161.0 race average @ 100% Opponent Strength, that's laps of 159s-162s during a fuel run, with the fastest practice/HH lap @ 162.3-162.9.  

The setup (*** see below_Anomaly):
1) fast.pta.sim__for the ai. You can use it, but it's made to get the ai to perform a specific way.
2) Race50 OW.pta.sim__race setup for the Player. Developed over ? hours and more than a thousand laps, specifically tuned to the grip values. 50 degree spoiler aids in passing. 
    Race45 OW.pta.sim__race setup for the Player. Developed over ? hours and more than a thousand laps, specifically tuned to the grip values. 45 degree spoiler, fastest setup for clean air, but passing is difficult.
    Race49 OW.pta.sim__race setup for the Player. Developed to compensate for a tight condition in the corner exit/acceleration zone when using Race50 OW.
3) Q OW.pta.sim__qualifying setup for the Player. An extension of the Race50 OW setup, there's not much room for qualifying speciality when the race setup has already pretty much maxed out all the variables, but it did allow enough improvement over the race version to warrant ai_qual_modifier = 1.038. (fastest Q lap: 165.108)
    Q49 OW.pta.sim__qualifying setup for the Player. An extension of the Race49 OW setup, there's not much room for qualifying speciality when the race setup has already pretty much maxed out all the variables, but it did allow enough improvement over the race version to warrant ai_qual_modifier = 1.038. (fastest Q lap: 164.910)

Driving:
1) It's better to enter the turn (T1, T3) slower than it is to drive in too deep. If you see RF tire smoke, you came in too hot.
2) Roll the first half (T1, T3) with part throttle and get back to full throttle as soon as possible for T2, T4.
3) Entering T1, T3: It's slightly faster if you roll into the turn using no brakes, but if you're carrying too much speed it'll cost you. Just a tap of the brake (with or without some throttle) on the approach (right before the turn in point) is a litte slower, but the braking sets the front for the turn and this method is a lot more predictable and consistent over course of the race.
4) The racing line through the entire corner (T1/T2, T3/T4): As long as you're below 3/4 track width, one line is not that different (timewise) from another, on the same end. That said, if you can run close to the inside line without scrubbing speed, that will yield the best laptime.
    I find T1/T2 to be slightly different than T3/T4. IMO, you can run T1/T2 just about anywhere. I find T3/T4 more limiting (and more speed sensitive), with an earlier corner entry preferable.
    A midtrack entry into T1/T3 followed by an early apex through T2/T4 will be the easiest line to drive consistently throughout a race.
5) Pitting: Get slowed down early, it's really tough to make the pit speed limit by the line if you haven't slowed early enough, and it's hard to ckeck your speed between turn in and the line when there's traffic.
6) Passing is tough, especially in heavy traffic. A slower car can hold you up for a few laps, an equal car (or close to it) can be downright discouraging.

There are only 36 pit stalls, plenty for an IndyCar simulation.
There are 2 paint lines designating where the pit speed limit takes effect. The 1st line is only for pit stalls 34, 35 & 36. The 2nd line, between pit stall 34 & 33, is for pitstalls 1-33. It was too hard to get slowed on the track (without getting rear ended), negotiate the tight pit road entry, and get to the speed before pit stall 33 (stall_32).

NOTE:
2x Pit Stop Frequency, [ ai_track_pta ] strategy_base_pitting_cost = 120.00 (default value).
If you run 4x Pit Stop Frequency use the alternate value, [ ai_track_pta ] strategy_base_pitting_cost = 25.00. Using the default value will cause many ai to run out of fuel.

*** Anomaly:
The track exhibits different driving characteristics depending on the NR2003 installation. IDK why, everything being equal, the track is a little tighter in one install than in another. It's like the real world, one day the track reacts to a particular setup, the next time it doesn't.
There are 2 primary setups to choose from. Race50 OW for a track that exhibits loose characteristics, and Race49 OW for a track that is tight when running the Race50 OW setup. Either may work for either track condition.
There are 2 corresponding qualifying setups, but again, either may work for either track condition.
Faster setups may be possible, I was satisfied that these were "close enough".

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Using track characteristics to produce an open wheel racing model using sportscar pyhsics (pta.exe).

Disclaimer:
You can't make sportcars handle and react like open wheel cars.
Open Wheel cars have tremendous front downforce provided by front wings, and they have large rear wings, so the total downforce is enough to run the car upside down in a tunnel. NR2003 has tape (the amount of it used is subject to engine overheating and eventual engine destruction) and a rear wing (pta), providing somewhat more grip than the spoiler of a cup car.
Open Wheel cars weigh 1500-1600 lbs. and have tremendous power to weight ratio. GT sports cars weigh 2700+ lbs. and have a significantly lower power to weight ratio. 

Nr2003 has car setup limitations, i.e. max settings that may come up short of what's required.
Qualifying has no option for less than a full tank of fuel. It may be possible to achieve historic race speeds, but not the qualifying speed.

The object of the exercise is to get open wheel racing characteristics using sportscar physics. The challenge is to get a mule to perform like a thoroughbred horse.
The only way to try and compensate for (some of) the lack of downforce/grip-level is to crank up the surface grip. 
Using extremely high grip values provide more tire adhesion, but it affects both ends of the car equally, unlike an independently adjustable front and rear wing. 
A loose car is a fast car. Using high grip values tightens the car, so the setup has to employ values beyond normal ranges to loosen the car and be able to take advantage of the increased surface grip.
Then there's the weight and the HP (or lack thereof). By increasing the surface grip of the track and reducing as much as possible the aero drag of the car, and depending on the track configuration, you might be able to realize the speed. However, there's no getting around the weight, a gt car is never going to be as nimble as an open wheel car. You can't reproduce the quick responsiveness of the OW car with a car of the mass of a GT. You can't reproduce that on the edge quality of an OW, that moment of in control to snap out of control, the gt physics will only yield a lazy turnaround.

In the end you hopefully wind up with something akin to open wheel, but it will never be a facsimile.

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Enjoy.
fortine_oo













