Tackling Tier 3

Both Cummins and Caterpillar choose the in-cylinder approach to reducing emissions.

The Environmental Protection Agency's (EPA) Tier 3 emissions standards take effect at the start of 2005, pushing requirements to sharply lower levels. Cummins is taking a number of steps to meet the lower levels, bringing improvements without increasing fuel consumption.

Tier 3 requirements, which phase in for different engine levels over the next three years, focus mainly on the various oxides of nitrogen (NOx). In the U.S., levels must decline by about 40% from Tier 2 levels now in existence, to 3.2 g/hp·h. European regulations kick in at around the same time, with fairly similar requirements.