Cummins’ four-cylinder QSB3.3 and QSB4.5 engines will meet EU Stage IIIB and U.S. EPA Tier 4 Interim off-highway emissions in 2012 across a 75- to 160-hp (56- to 119-kW) power range. The engines retain the same 3.3- and 4.5-L proven platforms and will be supplied as a fully integrated air-intake-to-exhaust system. Very low emissions are achieved via cooled exhaust gas recirculation for NOx control and exhaust aftertreatment for removing particulate matter. Both the cooled EGR system and the particulate aftertreatment unit have been developed for the four-cylinder platforms as a more compact and simplified version of the Tier 4 Interim technology incorporated into the six-cylinder QSB6.7 engine. The High Pressure Common Rail fuel system employed on the Tier 3 QSB3.3 and QSB4.5 is already capable for Tier 4 Interim and will require no major change. An upgraded turbocharger with electronic control will be used to manage EGR flow across the entire engine rpm range.