NASHVILLE, Tenn. Cummins has become the first U.S. diesel engine maker to announce it will meet the 2010 EPA emissions requirements without using selective catalytic reduction technology.

Instead, Cummins says it will meet the 2010 demands by using a combination of the XPI high-pressure common rail fuel system, improved cooled-exhaust-gas recirculation, advanced electronic controls, variable geometry turbochargers, and its own diesel particulate filter.

The Cummins announcement is in sharp contrast to earlier announcements by Detroit Diesel and Volvo/Mack, which said they would be using selective catalytic reduction technology to reduce the NOx level for their engines to meet the 2010 emissions levels mandated by the U.S. Environmental Protection Agency.

Selective catalytic reduction is a relatively new and controversial technology for U.S. diesel engine builders because it requires that urea be introduced into heated exhaust, causing it to break down into ammonia. The ammonia, in turn, reacts with the NOx in a catalytic converter to produce nitrogen and water.

It is being used by European-based engine makers, like Volvo. (See Oct. 1 issue of Bus & Motorcoach News.)

And while Cummins' heavy-duty diesel engines will not be using selective catalytic reduction, its medium-duty engines will adopt the technology.

For midrange engines, Cummins said there is a different set of priorities, including more diverse applications and the need for a wide power range and greater power density.

In addition to performance needs, Cummins says selective catalytic reduction is operationally more attractive for midrange situations than long-haul heavy-duty applications because the rate of urea consumption is lower and because midrange equipment typically returns to base daily for fueling and maintenance.

For many midrange applications, fleets will be able to replenish urea in sync with their oil change intervals, said Jeff Weikert, executive director of midrange engineering.

Cummins also announced that its 2010 engine line-up in North America will include 11.9-, 15- and 16-liter models. All will share a common architecture that includes the high-pressure common rail fuel system, said Ed Pence, vice president and general manager of Cummins' heavy-duty engine business. "This is the first time in nearly 20 years we've had common architecture across our heavy-duty products," said Pence.

The high-pressure common rail fuel system, which was designed and built by a Cummins-Scania joint venture, offers improved performance and cleaner exhaust by maintaining high injection pressures regardless of engine speed, Cummins said.

Cummins' approach toward lowering NOx for 2010 is to continue reducing the amount of oxygen introduced into the combustion process. Reducing the airflow not only reduces NOx but also produces other benefits, including high power density, minimum heat rejection and optimal fuel economy, said Steve Charlton, Cummins executive director of heavy-duty engineering.

And with less oxygen introduced into combustion, less oxygen comes out for use in cooled EGR, further improving performance and emissions control. "It's a virtuous circle," Charlton said.

Cummins said it chose its solution with an eye toward lowering complexity and eliminating the need to purchase and manage urea.

Many fleets "will take a deep sigh of relief" that they will not have to deal with the complexities introduced by urea and selective catalytic reduction technology, added Pence.