EPA's new regs for small spark-ignition engines

Diesel Progress North American Edition, Oct, 2008

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The United States Environmental Protection Agency (EPA) has finalized a new emissions control program designed to reduce hydrocarbons (HC), nitrogen oxides (N[O.sub.x]) and carbon monoxide (CO) emissions from small spark-ignition engines by about 35%, the agency said. The new exhaust emissions standards will take effect in 2011 or 2012, depending on the size of the engine. The final rule also includes new standards to reduce evaporative emissions from the fuel systems on these engines.

First proposed May 23, 2006, the regulations cover 10 categories of nonroad spark-ignition engines, ranging from lawn and garden equipment to airport service equipment. For complete details on this regulation see http://www.epa.gov/otaq/equip-ld. htm. EPA has also issued a new regulation covering gasoline boats and personal watercraft, details of which can be found at http://www.epa.gov/ otaq/marinesi.htm.

The new regulations cover emissions of HC, N[O.sub.x] and CO from a variety of nonroad engines, equipment and vessels. EPA said the controls for these products have been combined into one rulemaking because the engines and vehicles involved share many common characteristics. The differences in the design and use of these engines led the agency to adopt separate emissions standards for each group:

* Small Nonroad Spark-Ignition Engines and Equipment: spark-ignition (SI) nonroad engines rated below 25 hp used in household and commercial applications, including lawn and garden equipment, utility vehicles, generators, and a variety of other construction, farm and industrial equipment.

* Marine Spark-Ignition Engines and Vessels: spark-ignition engines used in marine vessels, including outboard engines, personal watercraft and sterndrive/ inboard engines.

Specifically for nonroad engines, EPA is adopting HC N[O.sub.x] exhaust emissions standards of 10 g/kW-hr for Class 1 engines starting in the 2012 model year and 8 g/kW-hr for Class 2 engines starting in the 2011 model year. The agency said compliance to these standards will likely be met by improving fuel systems, engine combustion and in some cases adding catalysts. The standards are also consistent with the requirements recently adopted by the California Air Resources Board (CARB).

For spark-ignition engines used in marine generators, EPA is adopting a more stringent Phase 3 CO emissions standard of 5 g/kW-hr. This applies equally to all sizes of small SI engines used in marine generators.

Further, EPA is adopting new evaporative emissions standards for both handheld and nonhandheld equipment. The new standards include requirements to control fuel tank permeation, fuel line permeation and diffusion emissions. For nonhandheld engines EPA will also require control of running losses.

In addition, the agency is adopting a more stringent level of emissions standards for outboard and personal watercraft engines starting with the 2010 model year. The HC N[O.sub.x] standard for engines producing less than or equal to 5.7 hp maximum power is 30 g/kWh. Engines producing greater than 5.7 hp have an HC N[O.sub.x] standard that gradually increases based on the engine's maximum power.

The CO standard for engines producing less than or equal to 53.6 hp gradually increases based on the engine's maximum power. The CO standard for engines with maximum power greater than 53.6 hp is 300 g/kWh.

The agency said it expects manufacturers to meet these standards with improved fueling systems and other in-cylinder controls. The federal levels of the HC N[O.sub.x] standards are consistent with the requirements recently adopted by CARB with the addition of a first-ever CO standard for this category of nonroad engines.

There are also new exhaust emissions standards for sterndrive and inboard marine engines. The standards are 5 g/kW-hr for HC NOx and 75 g/kW-hr for CO starting with the 2010 model year. Again, EPA expects these regulations will lead to the use of three-way catalysts and closed-loop fuel injection. To ensure proper functioning of these emissions control systems in use, EPA is requiring manufacturers to diagnose engines for failure in the emissions control system.

For sterndrive and inboard marine engines above 500 hp with high-performance characteristics ("SD/I high-performance engines"), EPA is adopting a CO standard of 350 g/kW-hr.

Further, EPA is adopting an HC N[O.sub.x] standard of 20 g/kWh for high-performance engines producing between 500 and 650 hp in 2010 followed by a tightened standard of 16 g/kWh in 2011. For high-performance engines producing greater than 650 hp, there will be a HC N[O.sub.x] standard of 25 g/kWh in 2010 and 22 g/kWh in 2011.

The emissions standards described relate to engine operation over a prescribed duty cycle for testing in the laboratory. EPA is also adopting "not-to-exceed" standards that require manufacturers to maintain a certain level of emissions control when engines operate under normal speed-load combinations that are not included in the certification duty cycle.