as far as i know, controlled yung diet nila before every race, since lunch ang meal before the race. about sa wee-wee, a driver sweats out water in his body so di na yun iihi. a driver actually loses about 3 pounds per race due to heavy sweating.
yan nga ang alam ko. they piss in their suits or have a tube attached to their wieners or something like that. I think doing the number 2 would be the farthest thing from their minds. sa taas ng stress levels during a race, pano mo magagawang i-relax yung ass muscles mo to take a dump? Unless siguro may diarrhea yung driver in which case he wouldn't have started the race in the first place. :D
We'll likely never know if anyone did win a GP like that, but we do know someone who lost a SS like that... Alister McRae was featured on star sports (last year) stopping his car in the middle of a stage and taking a leak!