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A two-phase study was performed to establish a standard diesel exhaust composition which could be used in the future development of light-duty diesel exhaust aftertreatment. In the first phase, a literature review created a database of diesel engine-out emissions. The database consisted chiefly of data from heavy-duty diesel engines; therefore, the need for an emission testing program for light- and medium-duty engines was identified. A second phase was conducted to provide additional light-duty vehicle emissions data from current technology vehicles. Engine-out diesel exhaust from four 2004 model light-duty vehicles with a variety of engine displacements was collected and analyzed. Each vehicle was evaluated using five steady-state engine operating conditions and two transient test cycles (the Federal Test Procedure and the US06). Regulated emissions were measured along with speciation of both volatile and semi-volatile components of the hydrocarbons.

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.