Cal. Code Regs. tit. 13 § 1956.9
1973 and later model-year heavy-duty engines that have been retrofitted to produce emissions less than the original certification emission level may be certified to optional emission standards as follows:
(X - n x 0.2) grams per brake horsepower-hour
where X = 0.75 x new engine total hydrocarbon standard for the engine's model year, with the further requirement that X is rounded down to the nearest lower 0.2 grams per brake horsepower-hour increment; and where n is an integer such that n x 0.2 is greater than or equal to zero. For diesel engines, X = 0.75 x original emission certification value for the engine's model year. For engines originally certified to a combined hydrocarbon plus oxides of nitrogen standard, X = 0.75 x original engine certification standard pro-rated by the hydrocarbon portion of the original emission certification level. If the original certification levels are not available, the hydrocarbon baseline standard shall be prorated by the hydrocarbon and oxides of nitrogen values of the next later model year with separate hydrocarbon and oxides of nitrogen standards.
For engines originally certified to an optional non-methane hydrocarbon standard,
(X - n x 0.2) grams per brake horsepower-hour
where X = 0.75 x new engine non-methane hydrocarbon standard for the engine's model year, with the further requirement that X is rounded down to the nearest lower 0.2 grams per brake horsepower-hour increment; and where n is an integer such that n x 0.2 is greater than or equal to zero. For diesel engines, X = 0.75 x original emission certification value for the engine's model year.
(X - n x 5.0) grams per brake horsepower-hour)
where X = 0.75 x new engine carbon monoxide standard for the engine's model year, with the further requirement that X is rounded down to the nearest lower 5 grams per brake horsepower-hour increment; and where n is an integer such that n x 5.0 is greater than or equal to zero. For diesel engines, X = 0.75 x original emission certification value for the engine's model year.
(X - n x 0.5) grams per brake horsepower-hour
where X = 0.75 x new engine oxides of nitrogen standard for the engine's model year, with the further requirement that X is rounded down to the nearest lower 0.5 grams per brake horsepower-hour increment; and where n is an integer such that n x 0.5 is greater than or equal to zero. For engines originally certified to a combined hydrocarbon plus oxides of nitrogen standard, X = 0.75 x original engine certification standard, pro-rated by the oxides of nitrogen portion of the original emission certification level. If the original emission certification levels are not available, the oxides of nitrogen baseline standard shall be pro-rated by the hydrocarbon and oxides of nitrogen values of the next later model year with separate hydrocarbon and oxides of nitrogen standards.
(X - n x 0.05) grams per brake horsepower-hour
where X = 0.75 x new diesel engine particulate matter standard for the engine's model year, with the further requirement that X is rounded down to the nearest lower 0.05 grams per brake horsepower-hour increment; and where n is an integer such that n x 0.05 is greater than or equal to zero. For diesel engines that were not originally certified to a particulate matter emission standard, X = 0.75 x 0.6 grams per brake horsepower-hour. Gasoline engines may not be certified to an optional exhaust emission standard for particulate matter.
Cal. Code Regs. Tit. 13, § 1956.9
Note: Authority cited: Sections 43701 (b) and (c), Health and Safety Code. Reference: Sections 39002, 39003, 43000, 43004, 43006, 43008, 43013, and 43108, Health and Safety Code; and Sections 27156, 38391 and 38395, Vehicle Code.