In previous years, EPA regulations have been more permissive when dealing with vehicle emission standards. But now, the EPA standards have become more strict, and have continued to so in the successive years.

The Tier 2 regulations introduced more stringent numerical emission limits relative to the previous Tier 1 requirements. A number of additional changes made the standards more stringent for larger vehicles. Under Tier 2 regulations, the same emission standards apply to all vehicle weight categories, i.e., cars, minivans, light-duty trucks, and SUVs.

In Tier 2, the applicability of light-duty emission standards has been extended to cover some of the heavier vehicle categories. The Tier 1 standards applied to vehicles up to 8500 lbs GVWR. The Tier 2 standards apply to all vehicles that were covered by Tier 1 and, additionally, to "medium-duty passenger vehicles" (MDPV). The MDPV is a new class of vehicles that are rated between 8,500 and 10,000 lbs GVWR and are used for personal transportation. This category includes primarily larger SUVs and passenger vans. Engines in commercial vehicles above 8500 lbs GVWR, such as cargo vans or light trucks, continue to certify to heavy-duty engine emission standards.

The same emission limits apply to all vehicles regardless of the fuel they use. That is, vehicles fuelled by gasoline, diesel, or alternative fuels all must meet the same standards. Since light-duty emission standards are expressed in grams of pollutants per mile, vehicles with large engines (such light trucks or SUVs) have to use more advanced emission control technologies than vehicles with smaller engines in order to meet the standards. The EPA Tier 2 program uses a three-tiered compliance strategy. Pre-production evaluation is used to certify vehicles prior to sale. A production evaluation is used on the assembly line for early evaluation of production vehicles. Finally in-use evaluation is used to verify properly maintained vehicles after several years of use. The Tier 2 regulation brought new requirements for fuel quality. Cleaner fuels are required by advanced emission after treatment devices (e.g., catalysts and particulate filters) that are needed to meet the regulations.

Sulfur Levels in Gasoline - The program requires that most refiners and importers meet a corporate average gasoline sulfur standard of 120 ppm and a cap of 300 ppm beginning in 2004. Since 2006, the average standard has been reduced to 30 ppm with an 80 ppm sulfur cap. Temporary, less stringent standards applied to some small refiners through 2007. In addition, temporary, less stringent standards applied to a limited geographic area in the western USA for the 2004-2006 period.

Diesel Fuel Quality - Diesel fuel of maximum sulfur level of 15 ppm (known as the ultra low sulfur diesel, ULSD) was made available for highway use beginning in June 2006. The reduction of sulfur content in diesel fuel was legislated by the EPA as a part of the 2007-2010 emission regulation for heavy-duty engines.

Tier 2 Certification Bins - The Tier 2 emission standards are structured into 8 permanent and 3 temporary certification levels of different stringency, called "certification bins", and an average fleet standard for NOx emissions. Vehicle manufacturers have a choice to certify particular vehicles to any of the available bins. When fully implemented in 2009, the average NOx emissions of the entire light-duty vehicle fleet sold by each manufacturer have to meet the average NOx standard of 0.07 g/mi. The temporary certification bins (bin 9, 10, and an MDPV bin 11) with more relaxed emission limits are available in the phase-in period and expire after the 2008 model year.

Tier 2 vehicles are those meeting the requirements of one of the available bins and that are used to meet the requirement that a percentage of the fleet have average NOx emissions of 0.07 g/mile. During the phase-in period, the rest of the fleet not used to comply with the 0.07 g/mile NOx average are referred to as interim non-Tier 2 vehicles. They must still meet the requirements of one of the available bins but have more relaxed fleet average requirements.

These EPA regulations are very important when it comes to your testing equipment. It means its time for a modification on current equipment or time for replacement equipment. Along with the EPA regulations there is the proposed Corporate Average Fuel Economy Plan (CAFE Plan). This plan would require that all vehicles have an average of 31.6 mpg by 2015 and 35 mpg by 2020.


Material referenced from www.dieselnet.com.