40 CFR §86.508-78

1. (a)The dynamometer shall have a single roll with a diameter of at least 0.400 metre.
2. (b)The dynamometer shall be equipped with a roll revolution counter for measuring actual distance traveled.
3. (c)Flywheels or other means shall be used to stimulate the inertia specified in § 86.529.
4. (d)A variable speed cooling blower shall direct air to the vehicle. The blower outlet shall be at least 0.40 m 2 (4.31 ft 2) and shall be squarely positioned between 0.3 m (0.98 ft) and 0.45 m (1.48 ft) in front of the vehicle's front wheel. The velocity of the air at the blower outlet shall be within the following limits (as a function of roll speed):
5. (e)The dynamometer shall comply with the tolerances in § 86.529.