This is the wiki page for the console command:
sv_freeplay_maxspeed
It allows changing the maximum velocity of the car (default: 2300 uu/s) in freeplay or workshop maps.
Usage[]
To change the maximum velocity of the car, open the console and type
sv_freeplay_maxspeed 3000
Replace 3000 with the desired maximum speed. 2300 is the default.