40 CFR 205.157-3 - Configuration identification.
(a) A separate vehicle configuration shall be determined by each combination of the following parameters:
(1) Exhaust system (engine): (i) Mufflers; (ii) expansion chambers; (iii) spark arrestors; and (iv) other exhaust system components.
(2) Air induction system (engine): (i) Intake muffler; (ii) intake ducting; and (iii) air cleaner element.
(3) Vehicle drive train: (i) Chain; and (ii) shaft.
(4) Transmission gear ratio: (i) Standard transmission; and (ii) automatic transmission.
(5) Cooling system configuration: (i) Natural air cooled; (ii) liquid cooled; and (iii) forced air cooled.
(6) Category parameters listed in § 205.157-2.