What EPA Tier 4 flexibility rules mean for manufacturers of nonroad equipment

Jan. 1, 2011, was the start date for nonroad equipment manufacturers to begin using diesel engines that comply with the U.S. Environmental Protection Agency’s (EPA) Tier 4 interim (4i) emissions regulations. With some exceptions, Tier 4i regulations now apply to all nonroad diesel engines 175 hp and greater — the power range most often used to power construction and industrial equipment, such as excavators, loaders, cranes, mining trucks and agricultural equipment. This latest round of exhaust emissions reductions takes aim at further reducing nitrogen oxides (NOx) and particulate matter (PM) in diesel exhaust. Tier 4 final regulations, which will further reduce NOx, are scheduled to be implemented beginning in 2014 and 2015, depending on horsepower categories.

EPA flexibility offers manufacturers a reprieve

Since the Tier 4i and Tier 4 nonroad engine regulations were proposed in 2003 and finalized in 2004, the EPA has been taking comments from equipment manufacturers about how to implement the rules with the greatest effectiveness and least adverse economic impact. It was determined that requiring equipment manufacturers to comply with the provisions of Tiers 1, 2, 3 and 4 under the current timetable would create an unreasonable economic burden for some — without accruing significant environmental benefits for the public.

So, beginning with the Tier 2 nonroad emissions standards, the EPA instituted a number of flexibility provisions designed to provide equipment manufacturers with some control over their transition to the new emissions standards. In general, these provisions have been extended to include implementation of Tier 4i and Tier 4 final. The flexibility rules allow pre-approved equipment manufacturers to use the previous-Tier engines in lieu of Tier 4i or Tier 4 final engines for up to a seven-year phase-in period.

Challenges of moving to Tier 4 engines

The new Tier 4i and Tier 4 engines are a culmination of a development process — with the goal of reducing emissions — that began in the 1990s. Since then, diesel engine manufacturers have made tremendous strides in reducing exhaust emissions through in-engine design changes and new technologies such as high-pressure common rail fuel injection, electronic controls, exhaust gas recirculation (EGR) and multistage turbocharging. In addition to being cleaner, engines have become more fuel efficient. Most major manufacturers now offer diesel engines that are Tier 2, Tier 3 and Tier 4i compliant, and will offer Tier 4 final engines in various engine horsepower categories.

However, one consequence of making the engines cleaner and more efficient is that the engine envelope has gotten somewhat larger, creating a challenge for nonroad equipment manufacturers to fit the engines into existing chassis. This is especially true with Tier 4 engines. When Tier 4 final regulations come into effect, this issue will become even more complicated. Equipment chassis will have to accommodate various exhaust aftertreatment devices on certain engines, such as selective catalytic reduction (SCR), tanks for diesel emissions fluid (DEF) and diesel particulate filters (DPF). The flexibility rules allow OEMs to avoid having to redesign equipment chassis to accommodate Tier 4i engines and then redesign them again to accommodate Tier 4 final engines.

General flexibility guidelines

Under the EPA’s flexibility rules, equipment manufacturers could delay the time when they would have to convert to Tier 4 final engines until 2020 or 2021, depending on which provision in the flexibility guidelines they select. For applications involving engines from 175 hp to \

Alternatively, if the OEM chooses to convert to Tier 4i engines immediately, it may be allowed to continue using Tier 4i engines until 2020. For applications involving engines 750 hp (560 kW) and above, an OEM may be allowed to use Tier 2 engines until 2017 (there are no Tier 3 engines in this power range). Alternatively, the OEM may be allowed to use Tier 4i engines until 2021, at which time Tier 4 final engines would be required.