16 September 2002
The US Environmental Protection Agency (EPA) has finalized the emission standards for large nonroad spark-ignition (SI) engines and recreational marine diesel engines. The regulation, proposed last September, was signed on 13 September 2002.
In this rule, the EPA adopted emission standards for several groups of nonroad engines that have not yet been subject to emission standards. These engines are (1) large SI engines (>19 kW) such as those used in forklifts and airport ground-service equipment; (2) recreational vehicles using SI engines such as off-highway motorcycles, all-terrain vehicles, and snowmobiles; and (3) recreational marine diesel engines.
With regard to Large SI engines, a two-phase program was adopted. The first phase of the standards go into effect in 2004 and are the same as those adopted in October 1998 by the California Air Resources Board for 2004. Manufacturers can meet these standards with three-way catalysts and closed-loop fuel systems. These standards will reduce combined HC and NOx emissions by nearly 75%. In 2007, these standards will be supplemented by setting limits that will require optimizing the same control technologies and will base emission measurements on a transient test cycle. New requirements for evaporative emissions and engine diagnostics also start in 2007.
For recreational vehicles, separate emission standards were adopted for snowmobiles, off-highway motorcycles, and all-terrain vehicles. For snowmobiles, a first phase of standards for HC and CO emissions was adopted based on a mixture of technologies ranging from clean carburetion and engine modifications to direct fuel injection two-stroke technology and some conversion to four-stroke engines, and second and third phases of emission standards for snowmobiles that will involve significant use of direct fuel injection two-stroke technology and conversion to four-stroke engines. For off highway motorcycles and all-terrain vehicles, standards were adopted based mainly on moving these engines from two-stroke to four-stroke technology with the use of some secondary air injection. Requirements were also adopted to address permeation emissions from all three types of recreational vehicles.
The emission standards for recreational marine diesel engines are comparable to those already established for commercial marine diesel engines. Exhaust and crankcase emission standards were adopted for recreational marine diesel engines with power ratings greater than or equal to 37 kW. Emission standards for HC, NOx, CO, and PM will become effective in 2006. Manufacturers will be able to use technology developed for land-based nonroad and commercial marine diesel engines. To encourage the introduction of low-emission technology, voluntary “Blue Sky” standards which are 40% lower than the mandatory standards were also adopted.
Source: US EPA