Lawn & Garden Equipment Engines With Reduced Emissions

Richard L. Parish  |  11/18/2004 10:31:53 PM

Small-engine-powered lawn and garden equipment you buy in the future will be more environmentally friendly and more expensive.
Although cars and trucks have been redesigned over the years to reduce emissions, small engines have not changed. They now make a more significant contribution to overall air pollution. Before regulation, small engine designers tried to optimize power, cost and durability, and the result was invariably fuel-rich combustion that led to higher emissions.
The U.S. EPA found that small spark-ignition engines of 25 hp or less contribute about 20 percent of hydrocarbon emissions and 23 percent of carbon monoxide emissions from all mobile sources (including cars and trucks). These small engines are used primarily in lawn and garden equipment. As a result of this perceived problem, EPA has issued new regulations on small engines.
Phase 1 of the new regulations went into effect in 1997 and required reductions in emissions of hydrocarbons, carbon monoxide, and nitrogen oxides. A more stringent Phase 2 is being phased in. It is causing major engine redesigning by manufacturers. You may see several changes in future products (and in some current new products).

4-Stroke Engines
Some manufacturers have elected to change from 2-stroke to 4-stroke engines on small hand-held tools such as string trimmers and hedge clippers. Since 4-stroke engines do not require oil mixed with the gasoline, they eliminate the burning of oil and reduce emissions. Also, the 2-stroke design results in up to 25 percent of the fuel being exhausted without combustion. Some applications, such as chain saws, will probably continue to use 2-cycle engines because the high rpm and power-to-weight ratio of 2-stroke engines cannot be matched by other engines.

Catalytic Converters
Some manufacturers are designing catalytic converters for small engines.

Fuel Injection
Fuel injection is more precise than the use of a carburetor and will help to reduce unburned fuel. Fuel injection is essential with catalytic converters.

Internal Engine Changes
Small engines can be completely redesigned to run at more optimum fuel-air mixtures (more like automobile engines). Redesign of intake and exhaust ports in 2-stroke engines can reduce unburned fuel emissions.

The EPA is concerned that small engines maintain their reduced-emission status as the engines age, and their regulations reflect this concern. This may mean you can expect better durability with less frequent tuneups than in the past.

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