Engine-based standard means an emission standard expressed in units of grams of pollutant per kilowatt-hour (or grams of pollutant per horsepower-hour) that applies to the engine. Emission standards are either engine-based or equipment-based. Note that engines may be subject to additional standards such as smoke standards.
40 CFR § 1068.30
The following definitions apply to this part. The definitions apply to all subparts unless we note otherwise. All undefined terms have the meaning the Clean Air Act gives to them. The definitions follow: