I did some test session with 5 different gen file to check the fps, and find the best settings to improve performance. I have very interesting results. I tested with 20 and 40 and 60 cars to compare the difference.
The different gen file example:
1. Same as before
2. Improved lod in and lod out
3. Tested with 3 lod's instead of 4
4. Tested with 2 lod's instead of 4
5. Tested with only the highest lod
Conclusion:
More lod's eat more fps, because at the same time with around 20-60 cars on the grid, need to load more lod's (objects) for the game engine. So with improved lod in and out settings, sometimes on the grid with a lot cars need to load (because of the distance between the first and last car) 2-3 lod's or all. The fps lost wasn't too much when i tested 40 or 60 cars compared to 20 cars on the grid. I checked the fps at the start of the race because more cars in a group. After few corner the fps went higher and higher. But i still got 67 fps at the start with 60 cars with high graphics settings.