What are Tier 3, Interim Tier 4, and Tier 4?
The US EPA operating in cooperation with C-ARB and EC have developed a schedule for CI engines that manages the exhaust emissions specifically targeting a wide variety of emissions, with those contributing to green house gasses and potential carcinogens being primary. This schedule, which is calculated chronologically from a selling standpoint, ranges from Pre-Tier to Tier 4. The US EPA Tier 3 (Euro Stage 2) began in 2006 for the non-road diesel engines that we are marketing today, and 2007 for the on-road diesels used in North America, Mexico excluded. Incidentally, Canada has an organization known as CEPA that regulates emissions within Canadian boundaries and those regulations primarily mirror the US EPA. There are, however, a few differences. You can find excellent resources detailing the US EPA regulations at epa.gov, dieselnet.org, and isuzuengines-info.com. The interim Tier 4 period (Euro Stage 3a), which is an optional stage as a precursor to Tier 4, began in 2008 for the model
