Gearing up for Tier 4

By 2014, the Environmental Protection Agency’s Tier 4 Final regulations will call for particulate matter (PM) and nitrogen oxide (NOx) levels to be reduced by more than 90% from Tier 3 levels. To meet these stringent standards, engine manufacturers anticipate employing a combination of advanced engine technology and exhaust aftertreatment. Their more immediate concern, however, is meeting Tier 4 Interim standards. Although less stringent than the Final regulations, the standards are still impressive from a clean-air viewpoint, requiring major reductions in both PM and NOx.

For diesel engines above the 173 hp range, the deadline to meet Tier 4 Interim is Jan. 1, 2011; a year later for those between 75 and 173 hp.

The technology
“To meet 2011 and 2012 Interim standards, most engine manufacturers are banking on two approaches,” says Illinois-based engine consultant John Fischer. “They will likely take the exhaust gas recirculation (EGR) path to reduce NOx. This technology essentially sends exhaust gas back into the engine where it works to lower heat and NOx production. A diesel particulate filter (DPF) will be added to control PM.”

The approach will combine with other engine technology that evolved over the years, including the use of turbochargers and electronic fuel delivery. What most manufacturers will avoid, at least for the time being, says Fisher, is selective catalytic reduction (SCR) technology that calls for injecting urea into the exhaust. “This technology, although quite popular in Europe, is more cumbersome since it involves an external tank to store the fluid.”

Announcements made by Cummins and John Deere Power Systems support his conclusions. Both have indicated that their Tier 4 Interim solution will include EGR and a particulate filter, along with proven engine technology enhancements. They have elected not to use a SCR system to meet Tier 4 Interim regulations.

Equipment impact
In April 2009, Cummins announced four-cylinder engines that would join its six-cylinder counterparts in meeting EPA Tier 4 Interim standards.

Hugh Foden, executive director, Cummins Off-Highway Business, explains: “Our four-cylinder development program for Interim Tier 4 was driven by the need to avoid the complexity of increasing displacement or overloading the engines with complications such as dual turbochargers. We have instead focused on minimizing the installation impact for our OEM customers with space-saving solutions such as the Cummins Direct Flow air filtration system, and we’ve scaled down the EGR and aftertreatment technology for these compact engines.”

He says the particulate filter for these engines replaces the OEM muffler and that the direct flow air filter represents up to 35% space savings compared to today’s radial filter. “Cummins is deeply involved with our OEM partners with our internal machine integration process and testing of Tier 4 engines and aftertreatment in off-highway equipment,” says Foden. “Pilot and field test equipment is being evaluated years in advance of the dates when EPA Tier 4 regulations take effect.”

As more sophisticated emissions-control technologies are added to diesel engines, upfront planning by OEMs is more important than ever. “Engine manufacturers will need to integrate Interim Tier 4 engines and aftertreatment into equipment designs,” says Geoff Stigler, manager of product marketing, John Deere Power Systems. The company, along with its distributors, have “increased resources dedicated to application integration reviews to ensure Interim Tier 4 products are applied efficiently and in conjunction with application guidelines.”

Stigler encourages OEMs to provide more operational transparency with appropriate guidance on equipment that uses Tier 4 Interim engines. “Clearly identifying components with labels and providing work instructions will help make users more comfortable with the adoption and implementation of technology.