The engine uses cooled exhaust gas recirculation (EGR) and a passive three-way catalyst to bring emissions down to those levels. A three-way catalyst (similar to the one used in gasoline-fueled cars) simultaneously converts NO_x, carbon monoxide (CO) and hydrocarbons (HC).

Current standards limit heavy-duty vehicle NO_x emissions to 2.2 g/bhp-hr. In 2007, the EPA requirement tightens to 1.2 g/bhp-hr, while the CARB standard drops all the way to 0.2 g/bhp-hr—the standard both agencies use for 2010.

(This difference in the two standards for 2007—and CARB’s doubts about diesel engines being able to meet its more stringent version of those standards—is the reason the agency is considering a proposal to require the purchase of all alternative fuel engines for transit buses. Earlier post. The hearing on that rule has been rescheduled to 20 October.)

The engine is designed to deliver better thermal efficiency and power density compared to current lean-burn natural gas engines. The 6-cylinder, 8.9-liter engine will deliver 320 hp (239 kW) and 1,000 lb-ft (1,356 Nm) of peak torque.

Scheduled for commercial launch in 2007, the engine is targeted for medium-duty truck, refuse and urban transit markets.

Development of the new ISL G natural gas engine, which is also funded with an initial $600,000 from the Department of Energy’s National Renewable Energy Laboratory, began some 30 months ago. OEM integration work for the 2007 ISL G has been initiated and pre-commercial demonstration in southern California, SCAQMD’s jurisdiction, will begin in months to come.

Cummins Westport will unveil a prototype of ISL G engine next week at the American Public Transportation conference (APTA).