Technical Standards

Both NOM-044-SEMARNAT-2006 (diesel) and NOM-076-SEMARNAT-2012 (gasoline) are applicable to new engines intended for use in vehicles with a gross vehicle weight greater than 3,857 kg (8,500 lbs.) or for new vehicles of this size.

Diesel Engine Standards

2018 to present

The revised standard, NOM-044-SEMARNAT-2017 sets A, AA, and B standards for heavy-duty engines and complete heavy-duty vehicles with a gross vehicle weight above 3,857 kg. The following table shows the timing and equivalent standards under U.S. or European regulations.

Limit values

Limit values for heavy-duty engines are shown in the following tables. Limits are set in grams per brake horsepower-hour (g/bhp-hr) for U.S.-aligned standards and in grams per kilowatt-hour (g/kWh) for Euro standards. Particle number and ammonia (NH3) limits are set as part of the Euro VI standards but have not been defined as limit values under EPA standards.

The useful life requirements for heavy-duty engine standards are as follows. Useful life is defined as the reference values used in durability tests as part of new engine or vehicle certification for design and testing of emission control systems. Useful life does not refer to, nor is it equivalent to, the manufacturer warranty or in-use vehicle emissions.

The standard includes optional alternative certification limits for medium-duty complete vehicles.

These limits can be used for medium-duty vehicles that are certified as complete vehicles, with testing done on a chassis dynamometer, rather than certified as an engine, with testing on an engine dynamometer. The 3B and 4B pathways for certification of complete vehicles were included in the original proposal, while 3A, 4A, and 4AA were added in the final standard.

On-Board Diagnostics and Compliance Inducements

The final standards require full OBD systems to be installed and operating on new vehicles meeting B standards. The type of OBD system must be listed in the certification documentation. Appendix A includes general OBD system requirements and a detailed description of the requirements—including monitoring thresholds and the systems and metrics to monitor—for OBD systems meeting the Euro VI and U.S. 2010 standards. As both U.S. and Euro standards require the full phase-in of OBD systems implementation of B standards, certification documentation under U.S. and Euro standards is used as the primary proof of compliance with OBD requirements.

The regulation requires that all vehicles meeting AA and B standards that are equipped with SCR systems (which require use of DEF for proper control of NO_x) are equipped with the full suite of operating systems of alerts and driver inducements to ensure the correct functioning of these systems. These fail-safes include lights, auditory alarms, and requirements to safely limit vehicle operation in all cases of improper use, including lack of DEF, poor-quality DEF, and insufficient consumption or dosing of DEF. Both European and U.S. systems described in Appendix B also include anti-tampering mechanisms to ensure that users do not evade these requirements.

1993-2018

Emission standards for new heavy-duty diesel engines first became effective in model year 1993 and were based on US 1991 and later requirements, including the US Environmental Protection Agency (EPA) FTP transient test cycle. Standards for MY 1993-1998 were equivalent to US standards and compliance could be demonstrated through certification by US EPA. Under NOM-044, engines in Mexico are provided compliance options and can meet European standards, as measured on the official European test cycles (ETC and ESC), as an alternative to the EPA-based standards; compliance with standards can be demonstrated through:

• Letter or proof issued by motor manufacturer, including earnings report issued by the testing laboratory,
• Certificate or proof issued by the Environmental Protection Authority of the country of origin or country of certification, or
• Certificate issued by Certification Bodies for the country of origin or country of certification.

In 2006, the standard NOM-044-SEMARNAT-2006 was adopted, establishing emission limits for total hydrocarbons, non-methane hydrocarbons, carbon monoxide, nitrogen oxides, particles, and opacity for new heavy-duty diesel engines. The standard allowed compliance with either US 2004 or Euro IV equivalent standards. The emission standards compliance timeline and equivalent limit values of the 1993 and 2006 standards are outlined below:

Gasoline, LPG, and NG Engine Standards

Emission standards for new heavy-duty engines fueled by gasoline, LPG, natural gas and other alternative fuels are specified by the NOM-076 standard, adopted in 1995, with later amendments in 2012. Similar to the diesel regulations, the emission standards are applicable to gas engines used in vehicles of GVW > 3,857 kg (8,500 lbs).

Gasoline and gaseous fueled engines are tested over the FTP transient test and must meet the US EPA-based emission standards shown in the following 2 tables.

Natural gas engines can alternatively be tested over the European Transition Cycle; relevant standards are show in the following table.

Manufacturers may choose to certify gasoline and gaseous fueled vehicles with GVW up to 6,356 kg (14,000 lbs) on a chassis dynamometer over the FTP-75 cycle. The table below summarizes emission standards for chassis-certified vehicles.