Developmental Fuels Emissions Evaluation

Emissions characterization of three, small off-road engines of less than 19 kW power rating operating on two developmental fuels and one reference fuel was performed. The two fuels were formulated to remove benzene completely, curtail sulfur, and in one blend, include a substantial proportion of ethyl tert-butyl ether (ETBE). The engines selected included one side-valve four-stroke engine, one overhead valve four-stroke engine and one handheld two-stroke engine. The engines were maintained in stock condition. Exhaust emissions from operation with the two developmental fuels were compared to those from operation with light-duty certification-grade gasoline. California Air Resources Board (CARB) Small Off-Road Engine (SORE) emissions test methods and test cycles were used to test the engines. Duplicate tests were performed on each engine using dilute sampling procedures. Hydrocarbon speciation was performed on one replicate with each fuel. The handheld, 2-stroke engine was also tested for particulate matter emissions. Results averaged for the three engines indicated emissions reductions in-total hydrocarbons (HC), carbon monoxide (CO), benzene, and 1,3-butadiene for the oxygenated fuel, and reductions in oxides of nitrogen (NOx), CO, benzene, and acetaldehyde for the non-oxygenated fuel. Despite substantial increases in formaldehyde with both developmental fuels, the total exhaust emissions of "EPA Toxic Compounds" were decreased in all engines by 41 to 57 percent, primarily attributable to the removal of benzene from the test fuels. Particulate matter emissions for the 2-stroke engine were reduced with both developmental fuels. In addition to exhaust emissions, a comparison was made between conventional gasoline and the developmental fuels with regards to evaporative emissions.