Appendix A to Part 1036 - Summary of Previous Emission Standards

Appendix A to Part 1036 - Summary of Previous Emission Standards

The following standards, which EPA originally adopted under 40 CFR part 85 or 86, apply to compression-ignition engines produced before model year 2007 and to spark-ignition engines produced before model year 2008:

(a) Smoke. Smoke standards applied for compression-ignition engines based on opacity measurement using the test procedures in 40 CFR part 86, subpart I, as follows:

(1) Engines were subject to the following smoke standards for model years 1970 through 1973:

(i) 40 percent during the engine acceleration mode.

(ii) 20 percent during the engine lugging mode.

(2) The smoke standards in 40 CFR 86.11 started to apply in model year 1974.

(b) Idle CO. A standard of 0.5 percent of exhaust gas flow at curb idle applied through model year 2016 to the following engines:

(1) Spark-ignition engines with aftertreatment starting in model year 1987. This standard applied only for gasoline-fueled engines through model year 1997. Starting in model year 1998, the same standard applied for engines fueled by methanol, LPG, and natural gas. The idle CO standard no longer applied for engines certified to meet onboard diagnostic requirements starting in model year 2005.

(2) Methanol-fueled compression-ignition engines starting in model year 1990. This standard also applied for natural gas and LPG engines starting in model year 1997. The idle CO standard no longer applied for engines certified to meet onboard diagnostic requirements starting in model year 2007.

(c) Crankcase emissions. The requirement to design engines to prevent crankcase emissions applied starting with the following engines:

(1) Spark-ignition engines starting in model year 1968. This standard applied only for gasoline-fueled engines through model year 1989, and applied for spark-ignition engines using other fuels starting in model year 1990.

(2) Naturally aspirated diesel-fueled engines starting in model year 1985.

(3) Methanol-fueled compression-ignition engines starting in model year 1990.

(4) Naturally aspirated gaseous-fueled engines starting in model year 1997, and all other gaseous-fueled engines starting in 1998.

(d) Early steady-state standards. The following criteria standards applied to heavy-duty engines based on steady-state measurement procedures:

Table 1 to Appendix A - Early Steady-State Emission Standards for Heavy-Duty Engines

Model year	Fuel	Pollutant
		HC	NOX + HC	CO
1970-1973	gasoline	275 ppm		1.5 volume percent.
1974-1978	gasoline and diesel		16 g/hp·hr	40 g/hp·hr.
1979-1984 a	gasoline and diesel		5 g/hp·hr for diesel, 5.0 g/hp·hr for gasoline	25 g/hp·hr.

^a An optional NO_X + HC standard of 10 g/hp·hr applied in 1979 through 1984 in conjunction with a separate HC standard of 1.5 g/hp·hr.

(e) Transient emission standards for spark-ignition engines. The following criteria standards applied for spark-ignition engines based on transient measurement using the test procedures in 40 CFR part 86, subpart N. Starting in model year 1991, manufacturers could generate or use emission credits for NO_X and NO_X + NMHC standards. Table 2 to this appendix follows:

Table 2 to Appendix A - Transient Emission Standards for Spark-Ignition Engines ^{a b}

Model year	Pollutant (g/hp·hr)
	HC	CO	NOX	NOX + NMHC
1985-1987	1.1	14.4	10.6
1988-1990	1.1	14.4	6.0
1991-1997	1.1	14.4	5.0
1998-2004c	1.1	14.4	4.0
2005-2007		14.4		d 1.0

^a Standards applied only for gasoline-fueled engines through model year 1989. Standards started to apply for methanol in model year 1990, and for LPG and natural gas in model year 1998.

^b Engines intended for installation only in heavy-duty vehicles above 14,000 pounds GVWR were subject to an HC standard of 1.9 g/hp·hr for model years 1987 through 2004, and a CO standard of 37.1 g/hp·hr for model years 1987 through 2007. In addition, for model years 1987 through 2007, up to 5 percent of a manufacturer's sales of engines intended for installation in heavy-duty vehicles at or below 14,000 pounds GVWR could be certified to the alternative HC and CO standards.

^c For natural gas engines in model years 1998 through 2004, the NO_X standard was 5.0 g/hp·hr; the HC standards were 1.7 g/hp·hr for engines intended for installation only in vehicles above 14,000 pounds GVWR, and 0.9 g/hp·hr for other engines.

^d Manufacturers could delay the 1.0 g/hp·hr NO_X + NMHC standard until model year 2008 by meeting an alternate NO_X + NMHC standard of 1.5 g/hp·hr applied for model years 2004 through 2007.

(f) Transient emission standards for compression-ignition engines. The following criteria standards applied for compression-ignition engines based on transient measurement using the test procedures in 40 CFR part 86, subpart N. Starting in model year 1991, manufacturers could generate or use emission credits for NO_X, NO_X + NMHC, and PM standards. Table 3 to this appendix follows:

Table 3 to Appendix A - Transient Emission Standards for Compression-Ignition Engines ^a

Model year	Pollutant (g/hp·hr)
	HC	CO	NOX	NOX + NMHC	PM
1985-1987	1.3	15.5	10.7
1988-1989	1.3	15.5	10.7		0.60.
1990	1.3	15.5	6.0		0.60.
1991-1992	1.3	15.5	5.0		0.25.
1993	1.3	15.5	5.0		0.25 truck, 0.10 bus.
1994-1995	1.3	15.5	5.0		0.10 truck, 0.07 urban bus.
1996-1997	1.3	15.5	5.0		0.10 truck, 0.05 urban bus.b
1998-2003	1.3	15.5	4.0		0.10 truck, 0.05 urban bus.b
2004-2006		15.5		c 2.4	0.10 truck, 0.05 urban bus.b

^a Standards applied only for diesel-fueled engines through model year 1989. Standards started to apply for methanol in model year 1990, and for LPG and natural gas in model year 1997. An alternate HC standard of 1.2 g/hp·hr applied for natural gas engines for model years 1997 through 2003.

^b The in-use PM standard for urban bus engines in model years 1996 through 2006 was 0.07 g/hp·hr.

^c An optional NO_X + NMHC standard of 2.5 g/hp·hr applied in 2004 through 2006 in conjunction with a separate NMHC standard of 0.5 g/hp·hr.

[86 FR 34406, June 29, 2021]