I have seen a deal on that once many years ago. It had records for different scale models, mostly cars. They would custom wind the motors and run them at higher voltages. don't know the speed, but at the time, the HO car record was held by a 12V model running on a 36V track.
I have a couple of engines that have pulled 200+ car consists on a 3% grade. Maybe I have one of those record holders and don't even know it!!! lol