Fleet V ehicle Data T estingChanging emissions standards Beginning with all heavy-duty truck engines manufactured on or after January 1, 2010, the U.S. Environmental Protection Agency issued new lowered NOx emissions standards. To meet these requirements, many heavy-duty engine OEMs, particularly those whose manufactured end products are found within Class 7 to Class 8 trucks, have implemented selective catalytic reduction (SCR).SCR requires the periodic addition of a urea-based diesel exhaust ?uid (DEF) to the heavy truck engine. The DEF is added to the exhaust stream in the presence of a catalyst. The interaction between the catalyst and ?uid results in the chemical conversion of unwanted NOx compounds into more environmentally friendly water and nitrogen gas. To achieve optimized NOx em

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