the only sim on PS3 is NASCAR 09 so you have to wait for GT5
Nfs: Shift sadly is the closest you will get to a sim and it's 1/2 an arcade racer. grid is more sim but you can only drive the cars they give you and there is no tuning, same with dirt 2.
http://www.gamefly.com/RentalMediaTi...Size=15&page=1