Or maybe that this kind of things are planned for future versions with new/modified physics/graphics engines. It's just a matter of priority I guess because if they want it it now, they could build it now. It's not that the current engine is only limited to the things ISI had implemented in the gMotor engine "decades" ago. And that "old Audi prototype diesel" was pretty relevant as it was the first itteration of the later very succesful Audi R18 LMP1 car. And only later it became hybrid. Although my personal favorites are the R10 and R15. I just have something with the open cockpit LMP cars.