To me, it all depends on the size of the player model. You can use it to translate player model's height units to feet and make the measurement from there. (It can be variety depending on map maker design it to be that way.)
So, as for stock. Continue read below.
http://hce.halomaps.org/hek/references/general/halo_player_stats.html Quote from link above.
Quote: As a reference, the Master Chief is approximately 7 feet tall.
This makes the unit scale approximately 10 units = 1 foot or about 1 unit = 1.2 inches.
So, 2.13 m = 6.988189 ft which is about 7 feet. In units’ format, it will be 69.88189 units for master chief model.
To the point, meter translate to unit... it is 1 m = 3.28084 ft = 32.80840 units.
1 km = 1000 m = 3280.84 ft = 32808.4 units
In final result 32808.4 units per hour for 1 km/h. (yes I know it's off topic yet relative to first equation.)
Hmm... I think you would want to reverse the method plus use a stopwatch to time a warthog to be sure it's accurate?
P.S. your first m/s conversion is incorrect. It should be 0.277778 m/s since it is infinite after the 7's.
New info: if the warthog is 11 wu/s and only have the ratio of 0.275 value. Perhaps you can divide 0.275 and 11 wu/s then receive "40" wu/ratio (1.0 ratio).Hope this helps... somehow to you.