I have tested the AI LIMITER function. These are my findings:
Test setttings
Mod: CART 98
This mod has rcd files (talent files) which work. Difference between the fastest guys and slowest guys is 1.5-1.7 seconds in practice, with 1 guy always being a few tenths slower at 2.0-2.1 seconds of the pace (PJ Jones in the underpowered AAR Toyota)
Track: Indy 500 oval
I tested it on an oval since according to the json file it's effect is more for flatout tracks)
AI limiter settings: 0.0, 0.10, 0.22
I started at 0.22 because in another topic on AI performance someone suggested some player setting for great ai racing including the AI limiter setting of 0.22 . For clarity, i had 0.22 in the player.json and changed the setting in game to 0.0 or 0.10. I did not do this in the player file (no idea if this would have had a different outcome).
Other settings:
AI strength at 83%, AI aggression at 52%
Test runs: Multiple
I ran multiple test runs. A test run was a race with 27 AI and myself. I started at the back and parked the car in the pits after lap 1 and then watched the race with accelerated time on. Longest runs where full 200 laps, shortest were around 50. I probably did a dozen test runs.
My findings:
AI limiter at 0.22:
This was the value i started at. What i noticed was that the AI had great fights, with a bunch of passes for the lead and also a lot of 3 wide/3 car fights, while still respecting each other (no crashes). So that was nice.
However the bad thing (and also the reason to start testing with AI limiter) was that there was no clear seperation between the cars. Essentially before the 1st pitstops you'd have a long line of 27 cars staying together, like a train with a bunch of wagons. As i said with a lot of passing, but after 35 laps the leader and the 27th placed guy were within a couple of seconds. So even PJ Jones, the guy constantly 2 seconds of the pace in practice could keep up with everyone.
Some parts of this train broke up after the pitstops due to guys who lost a few seconds in the pits lost the 'tow' and could not keep up and they formed their own minitrains.
All in all a setting which for me was keeping the guys to close together and probably a bit to much passing as well.
AI limiter at 0.0:
Using AI limiter setting of 0.0 resulted in much clearer difference between the cars, and quickly 'minitrains' would start to form. It was always Andretti, Fittipaldi and Unser Jr. who would be up front on their own (all spread out) and then 3 mini trains. Those mini trains would have the same subtopguys in train 1, midpack guys in train 2 and backmaker guys in train 3. And PJ Jones would run by himself at the back of the field. The difference between these groups would slowly increase, with later in the race mini trains breaking up due to pitstops.
The negative of this setting was that there was no passing. At all. As in no passes, 0, nada, niente. You can see the positions per lap of the guys in the UI and those would just be straight lines with only the pitstops have an effect.
Basically, this setting would be useless for offline racing because there would be no passing at all.
AI limiter at 0.10:
This setting produced a nice mix of both worlds: You would see guys losing contact with the train and get a couple of different groups, but still also see passing. And still have the guys perform close to what you expect from their RCD/talent file and car performance combo.
So in short:
AI limiter at 0.0: Spread out according to the RCD files & vehicle performance, but no passing. 0 passes in 35 laps.
AI limiter at high setting: Racing is much, much closer with a lot of passing, but no breaks/cars stay together. After 35 laps just 5 seconds between p1 and p27
AI limiter somewhere in between: Mix of both, so spread out somewhat according to talent file, but close enough to actually race and pass. After 35 laps probably somewhere between 50 and 100 passes in total, and also gaps between the fastests and slowest cars. Only the subtop to midpack guys stayed together as long as they kept into the 'tow'.
Hope this helps.