I need some help

Hello, I have a problem with frames per second hits at the Daytona Race Track. I'm using the 2015 editions and BR16. Everywhere on the racetrack with the exception of the front stretch, im running 80 FPS to 140FPS. When I enter the tri oval on the front stretch, my FPS dips down too 2 to 5 FPS. I don't know why I seem to have a problem. I run iRacing and im locked at a solid 83 FPS with damn near everything turned on. Any help with this is greatly appreciated.
My specs:
GPU: Geforce GTX...

I need some help