I haven't seen a suggestion like this, so here i go.
There should be an option to add grille tape, or to be able to put on plastic covers to your car's grilles to increase front downforce.

I don't give a crap about the graphic of a piece of grille tape over the grille, all that is needed here is the simulation of having the grille closed up.

wouldn't that cause the engine to overheat?

Quote from bunder9999 :

wouldn't that cause the engine to overheat?

No, i meant covering the brake ducts for qualifying laps and oval racing.

To what end? The difference in the cars that don't already have adjustable downforce will be pretty minimal and if every car had it then any potential advantage would be lost.

A lot of times in oval racing, teams tape up the radiator and/or brake ducts to gain a little aero advantage during qualifying. Currently LFS doesn't model engine or brake heat, so it's not much use at the moment.