Cleaner Diesels Head Off-Road

Emissions requirements haven’t just tightened up for cars and trucks. Off-road construction and agricultural equipment will soon face a new federal Clean Air standard that slashes allowable exhaust emissions by more than 90 percent. And that prospect has left the makers of off-road engines scrambling to meet deadlines that start as early as next year.

The standard, which the U.S. Environmental Protection Agency refers to as Tier 4, calls for 90 percent reductions to both particulate matter (PM) and nitrogen oxides (NOx). It will also reduce the sulfur levels in non-road diesel fuel by more than 99 percent. The standard phases in from 2008 to 2015.

From a public health standpoint, Tier 4 looks like a no-brainer. According to EPA estimates, it will, by 2030, prevent about 12,000 premature deaths, 8,900 hospitalizations, one million lost work days, 15,000 heart attacks, 6,000 children’s asthma-related emergency room visits, 280,000 cased of respiratory problems in children, 200,000 cases of asthma symptoms in children and 5.8 million days of restricted adult activity every year.

From an engineering standpoint, however, the rule requires some brainpower.

“Tier 4 may well be the biggest engineering challenge the industry has faced,” says Joe Loughrey, president and chief operating officer of Cummins Inc.

At last month’s Con Expo-Con/Agg show in Las Vegas, prominent engine makers like Cummins, John Deere Power Systems and Caterpillar displayed new engines or discussed their plans for meeting the emissions challenge.

Cummins, to take one example, rolled out a 6.7-§¤ next-generation engine that showcases some of the existing on-highway emissions reduction technologies that will be leveraged to reduce emissions off-road. Called the QSB6.7, the engine features a cooled exhaust gas recirculation (EGR), a high-pressure common rail (HPCR) fuel system, integrated particulate filter aftertreatment, a variable-geometry turbocharger and a brand-new air filtration system with integrated air flow management capabilities.

Together these technologies not only promise to reduce emissions but also improve performance a bit. According to Ric Kleine, vice president of Cummins’ off-highway business, the QSB6.7 engine offers 90 percent PM reduction and a 45 percent NOx reduction, yet increases power output from 275 hp for the previous generation to 300 hp — in essence giving the new engine a power output more typical of a larger displacement engine.

Other engine makers are taking similar steps to integrate emissions reduction technologies that have been necessary on the highways. Bill Haushalter, vice president of transportation business development at Custom Sensors & Technologies (CST), says he’s seen an across-the-board interest from the engine maker in the pressure sensors used for EGR and diesel particulate filter (DPR) applications. “The engine makers are all following the same path taken by heavy-duty on-road vehicles,” he says.

	The QSB6.7 engine from Cummins features emissions reduction technologies that help it meet a tough new federal standard.