EPA10 and Newer Engines

The EPA mandates that all engines built after December 31, 2009 must reduce the level of emissions exhausted by the engine to the following levels:

• Nitrogen Oxides (NOx) – 0.2 g/bhp-hr

• Particulate Matter (PM) – .01 g/bhp-hr

To meet EPA guidelines, engines that are compliant with EPA10 and newer regulations use technology known as selective catalytic reduction (SCR) in the exhaust aftertreatment system (ATS). The ATS includes an aftertreatment device (ATD), with the addition of SCR to reduce NOx downstream of the engine. The SCR process requires the introduction of diesel exhaust fluid (DEF) into the exhaust stream.

After exhaust gases leave the engine, they flow into the ATS. First they flow into a two-part ATD, comprised of a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF). The DPF traps soot particles, then exhaust heat converts the soot to ash, in a process called regeneration (regen). After exhaust gases leave the DPF, a controlled quantity of diesel exhaust fluid (DEF) is injected into the exhaust stream. In the presence of heat, DEF is converted to ammonia gas, which reacts with NOx in the selective catalyst chamber to yield nitrogen and water vapor, which exit through the tailpipe.