Cummins QSF3.8 engine, with horsepower ratings from 85 to 132, meets EPA Tier 4-Final regulations with a minimum of exhaust aftertreatment. The 3.8-liter, four-cylinder engine controls particulate emissions in-cylinder, eliminating the need for either a diesel oxidation catalyst or a diesel particulate filter. A selective-catalytic-reduction (SCR) system, the only aftertreatment device required, reduces oxides of nitrogen. The SCR system, developed by Cummins Emissions Solutions, is designed to function at reduced exhaust temperatures and to require only minimal doses of diesel exhaust fluid. According to Cummins, the high efficiency of the SCR system also reduces the volume of exhaust gas being recirculated by the engine, reducing overall cooling demands. The new engine is equivalent in size and weight to the current QSB3.3 engine, says Cummins, and will facilitate the transition from Tier 4-Interim to Tier 4-Final for compact-equipment installations. Although larger in displacement, the QSF3.8, according to Cummins, achieves fuel efficiency similar to the 3.3-liter QSB3.3 and also delivers 10 percent more power and an 18-percent increase in peak torque. The new engine features a rear gear train, high-strength cast-iron block, and composite-material valve cover and oil pan. The Cummins Direct Flow air-filtration system, says the company, is designed with greater dust-holding capacity than that of similar-size filters, thus extending filter life. The high-pressure, common-rail fuel system uses a two-stage filtration process with Cummins NanoNet media, which, says the company, traps particles as small as 5 microns with less fuel-flow restriction.