Clean Fuel Fleet Program for Heavy-Duty SI and CI Engines, g/bhp·hr
Category* CO NMHC+NOx PM HCHO LEV (Federal Fuel) . 3.8 . . LEV (California Fuel) . 3.5 . . ILEV 14.4 2.5 . 0.050 ULEV 7.2 2.5 0.05 0.025 ZLEV 0 0 0 0 * LEV - low emission vehicle; ILEV - inherently low emission vehicle; ULEV - ultra low emission vehicle; ZEV - zero emission vehicle
Model Year 2004 and Later
In October 1997, EPA adopted new emission standards for model year 2004 and later heavy-duty diesel truck and bus engines. These standards reflects the provisions of the Statement of Principles (SOP) signed in 1995 by the EPA, California ARB, and the manufacturers of heavy-duty diesel engines. The goal was to reduce NOx emissions from highway heavy-duty engines to levels approximately 2.0 g/bhp·hr beginning in 2004. Manufacturers have the flexibility to certify their engines to one of the two options shown in Table 4.
EPA Emission Standards for MY 2004 and Later HD Diesel Engines, g/bhp·hr
Option NMHC + NOx NMHC 1 2.4 n/a 2 2.5 0.5
All emission standards other than NMHC and NOx applying to 1998 and later model year heavy duty engines (Table 1) will continue at their 1998 levels.
EPA established a revised useful engine lives, with significantly extended requirements for the heavy heavy-duty diesel engine service class, as follows:
• LHDDE - 110,000 miles/10 years
• MHDDE - 185,000 miles/10 years
• HHDDE - 435,000 miles/10 years/22,000 hours
The emission warranty remains at 5 years/100,000 miles.
The federal 2004 standards for highway trucks are harmonized with California standards, with the intent that manufacturers can use a single engine or machine design for both markets. However, California certifications for model years 2005-2007 additionally require the Supplemental Emission Test and NTE limits of 1.25 times the FTP standards. California also adopted a different standard for urban bus engines.
In October 1998, a court settlement was reached between the EPA, Department of Justice, California ARB and engine manufacturers (Caterpillar, Cummins, Detroit Diesel, Volvo, Mack Trucks/Renault and Navistar) over the issue of high NOx emissions from heavy-duty diesel engines during certain driving modes. Since early 1990’s, the manufacturers used engine control software that caused engines to switch to a more fuel efficient (but higher NOx) driving mode during steady highway cruising. The EPA considered this engine control strategy an illegal “emission defeat device”.
Provisions of the Consent Decree included the following:
• Civil penalties for engine manufacturers and requirements to allocate funds for pollution research
• Upgrading existing engines to lower NOx emissions
• Supplemental Emission Test (steady-state) with a limit equal to the FTP standard and NTE limits of 1.25 × FTP (with the exception of Navistar)
• Meeting the 2004 emission standards by October 2002, 15 months ahead of time