(a) Act means Part A of Title II of the Clean Air Act, 42 U.S.C. 7421 et seq. (formerly 42 U.S.C. 1857 et seq.) as amended.

(b) Aftermarket part means any part offered for sale for installation in or on a motor vehicle after such vehicle has left the vehicle manufacturer's production line.

(c) Aftermarket part manufacturer means:

(d) Agency means the Environmental Protection Agency.

(e) Certified aftermarket part means any aftermarket part which has been certified pursuant to this subpart.

(f) Emission warranty means those warranties given by vehicle manufacturers pursuant to section 207 of the Act.

(g) Emission-critical parameters means those critical parameters and tolerances which, if equivalent from one part to another, will not cause the vehicle to exceed applicable emission standards with such parts installed.

(h) Engine family means the basic classification unit of a vehicle's product line for a single model year used for the purpose of emission-data vehicle or engine selection and as determined in accordance with 40 CFR 86.078-24.

(i) Vehicle or engine configuration means the specific subclassification unit of an engine family or certified part application group as determined by engine displacement, fuel system, engine code, transmission and inertia weight class, as applicable.

(j) Certification vehicle emission margin for a certified engine family means the difference between the EPA emission standards and the average FTP emission test results of that engine family's emission-data vehicles at the projected applicable useful life mileage point (i.e., useful life mileage for light-duty vehicles is 50,000 miles and for light-duty trucks is 120,000 miles for 1985 and later model years or 50,000 miles for 1984 and earlier model years).

(k) Applications means all vehicle or engine configurations for which one part is being certified as set forth in the aftermarket part manufacturer's notification of intent to certify pursuant to § 85.2115(a)(1).