At present, the regulation of emissions from heavy-duty diesel vehicles with a GVWR of greater than 8,500 lbs. stand at the levels stipulated during 1998: 4.0 g/bhp-hr of NOx, 0.1 g/bhp-hr of PM, and 1.3 g/bhp-hr of Non-Methane Hydrocarbons (NMHC). New regulations are to be phased in, however, from 2004 to 2006, and will reduce the present level of permissible NOx and NMHC by half.
Most manufacturers are attempting to accommodate these stricter regulations by reducing NOx with exhaust gas recirculation (EGR) system, while applying diesel particulate filters (DPF) against the larger PM production resulted by the use of EGR.
In fact, the seven American manufacturers of heavy-duty diesel engines that were penalized for eliminating functionality from emission control devices in order to improve highway fuel economy in 1998 have been ordered to expedite application of this technology on all engines manufactured beginning in October of 2002.
Regulations are scheduled to be tightened again in 2007, which will require additional advances in technology for emission control devices, when permissible levels are reduced to 0.2 g/bhp-hr for NOx, 0.01 g/bhp-hr for PM, and 0.14 g/bhp-hr for NMHC. These more stringent levels of regulation are to be phased-in over a four-year period with 100% compliance (based on sales volume) mandated by 2010.
Table 5 shows permissible emission levels and the time frame within which these levels must be reached. Table 6 shows the phasing-in over a four-year period of compliance levels based on sales volumes.
