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reductant and a catalytic converter to achieve the NOx emission reduction now required by the U.S. EPA and Environ- ment Canada. The increased EGR ap- proach recirculates a significantly larger portion of the engine’s exhaust gas back to the engine, where the NOx emission re- duction occurs. The increased EGR ap- proach is often referred to as an “in-cylinder” approach. SCR accomplishes NOx reduction by mixing the oxides of nitrogen in the ex- haust gases with a reductant, most com- enhanced EGR approach also requires greater cooling capacity for the engine. “Although it’s new to North America, SCR technology is currently used in more than 600,000 trucks around the world,” said Hunter. “SCR has proven its ability to meet European Union emission reduction requirements for many years.” From an engine performance stand- point, because the SCR aftertreatment sys- tem handles the NOx reduction downstream from the engine, Hunter said SCR allows manufacturers to develop en- are expected to enjoy a fuel economy im- provement. That’s because the SCR cata- lyst is doing the work, and not the engine, to get nitrogen oxide levels down below the EPA threshold. “We believe that trucks with engines that are less complex and offer longer life, better fuel economy, greater reliability, im- proved driveablity, and higher power den- sity for better throttle performance, will retain higher resale values,” Hunter added. “While full-service leasing offers ben- efits, including the ability to preserve lines Working with a full-service leasing company can help make selecting a truck for your fleet easier and more affordable. monly a solution of urea and de-ionized water also known as diesel exhaust fluid (DEF). The exhaust passes through a de- composition tube, where the DEF is intro- duced through a dosing valve. The exhaust then passes through a cylindrical chamber, also known as the SCR catalyst. Here the DEF reacts with the NOx, breaks it down, producing oxidizing ammonia. The oxidiz- ing ammonia chemically reacts with the NOx, converting the pollutants into nitro- gen, water and tiny amounts of carbon dioxide. The SCR catalyst contains a honeycomb-like substrate, which also re- acts with the pollutant, converting it into nitrogen and water. Increased EGR accomplishes NOx emission reduction by increasing the amount of engine exhaust gases into the engine cylinder, slowing and cooling the combustion process. Increased EGR doesn’t require introducing DEF into the exhaust stream to reduce NOx, but it does require more fuel to be injected into the diesel particulate filter for active regenera- tions. The increased heat created with the www.landscapeirrigation.com gines that last longer and work more effi- ciently. According to Hunter, in the develop- ment phase of the PACCAR PX line of engines, engineers looked at both high- flow EGR systems as well as SCR to attain emission reductions. “PACCAR engineers believe SCR, in conjunction with moder- ate EGR, provides the most efficient and effective way to meet the strict EPA 2010 emission regulations,” Hunter added. Not all SCRs built the same Operators looking at different SCR en- gine choices should also consider that even among different SCR engines, there are two major choices that have emerged. One common SCR engine platform uses iron zeolite in the aftertreatment system catalyst while the other uses copper zeolite. “PACCAR engineers found copper ze- olite is much more efficient at reducing oxides of nitrogen at normal engine oper- ating temperatures than iron zeolite,” said Hunter, “This means that engines using copper zeolite as the aftertreatment catalyst of credit for core business projects or other revenue-generating endeavors, it can also help make choosing a truck with 2010 engine technology easier and more affordable. If you’re considering acquiring trucks with 2010 engines for your fleet operation, consider your two choices in emission control, and know full-service leasing may offer the best way to go about it.” LI Article provided by PACCAR Leasing Company (PacLease), one of the fastest-growing commercial truck leasing companies in the trans- portation industry. PacLease is a part of the fi- nancial services group of PACCAR Inc, a global technology leader in the design, manufac- ture and customer support of high-quality light-, medium- and heavy-duty trucks under the Kenworth, Peterbilt and DAF nameplates. PACCAR also designs and manufactures ad- vanced diesel engines, and has conducted exten- sive testing of 2010 U.S. EPA-compliant engines in many applications, climates and duty cycles. For more information, visit www.pac lease.com or www.paccarengines.com. Landscape and Irrigation 11