it should add ALOT of time..to make it a few seconds would be unrealistic, to change everything (tires, suspension, steering, gearing etc.) would take minutes...which im sure isnt worth it in the pits. too unrealistic of a feature imo.
drove it around in singleplayer for a bit, went online..had two races, both crashes by idiots and people who cant drive...never touched the car again until i can find a bf1 race with people who can drive, im fine for now