Engine manufacturers using selective catalytic reduction (SCR) emission control technology have new federal guidance allowing them to more gradually “derate” systems when diesel exhaust fluid (DEF) depletes.
U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin announced during the Iowa State Fair last week the new action to designed to protect American farmers, truckers and other diesel equipment operators from sudden speed and power losses caused by DEF systems.
“We have heard loud and clear from small businesses across the U.S. that the current DEF system is unacceptable,” Zeldin said in a statement. “It is unacceptable that farmers, truckers, construction workers, and many other small businesses continually experience failures of diesel-powered equipment when they need it most—costing millions of dollars in lost productivity. Today, we are responding to those concerns by calling on manufacturers to take action to update their software and eliminate the unnecessary sudden loss of power and frustrating shutdowns that too many Americans have experienced.”
EPA issued the guidance urging diesel engine and off-road farm equipment manufacturers to revise DEF system software in existing vehicles and equipment to prevent these sudden shutdowns. Starting with model year 2027, all new diesel on-road trucks and motorcoache amust be engineered to avoid sudden and severe power loss after running out of DEF.
EPA said it also has a fix for derate issues in legacy diesel vehicles with SCR.
“To fix the problem for vehicles already in use, EPA’s new guidance, developed in collaboration with manufacturers, will work to ensure that the necessary software changes can be made on the existing fleet,” the press release notes. “In addition to providing certainty to manufacturers about how EPA wants this issue resolved, the agency is not requiring separate approvals beyond that provided in EPA’s guidance. This ensures that bureaucratic steps do not delay manufacturers’ ability to put solutions into the field.”
Since 2010, SCR has used on-board diagnostics sensors to detect when DEF runs out or diesel particulate filters clog and then initiate a rapid derate of the engine. Within four hours of DEF depletion, vehicles automatically slow to five miles per hour.
But the results for industries have been “catastrophic,” said EPA, as disruptions have occurred to logistics, agriculture and construction. Several diesel engine manufacturers also initiated recalls over their SCR technology. Cummins recalled 2010 to 2015 medium- and heavy-duty engines, including the ISB 6.7 for school buses, because the SCR unit catalysts degraded faster than expected.
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“At Cummins, we recognize our responsibility in powering some of the country’s most economically vital applications, from the buses that take our kids to and from school to the trucks that deliver critical goods,” a statement from the company reads. “Collaboration with our customers is at the heart of what we do, ensuring we deliver solutions that meet their business needs while continuously innovating to improve fuel efficiency, reduce costs and enhance reliability. SCR is a widely accepted, proven technology utilized in many applications, and we are committed to working closely with the EPA and the select customers affected by SCR inducements. Together, we aim to provide regulatory certainty, greater flexibility and the dependable solutions that contribute to the American economy.”
Daimler Truck North America told School Transportation News it welcomes the new guidance.
“We are supportive of the efforts to provide more flexibility with regard to DEF inducement and are actively working on solutions to support our customers,” the statement reads.
The Engine Technology Forum and several other organizations also support the new derate guidance.
“EPA has heard from users of diesel trucks, tractors and equipment and, working with manufacturers, has responded with these adjustments to improve operational performance while ensuring emissions integrity,” Executive Director Allen Schaeffer said. “EPA’s announcement [Aug. 12] provides new guidance that allows manufacturers to adjust these systems to ensure that farmers, motor coach operators, and truckers, who all rely on diesel engines and equipment, will be able to complete critical work with sufficient lead time for scheduling maintenance and repairs.”
