EXHAUST AFTER-TREATMENT IN HEAVY-DUTY MOTOR VEHICLES

Controlling exhaust after-treatment in a heavy-duty motor vehicle includes operating a diesel engine of a heavy-duty truck such that the diesel engine generates an exhaust gas flow that enters an exhaust after-treatment system (100) of the heavy-duty truck, the exhaust after-treatment system including a selective catalytic reduction system (116), measuring a level of NOx gases in the exhaust gas flow upstream (at 108) and downstream (at 118) of the selective catalytic reduction system (116), and controlling a diesel exhaust fluid injector (110) upstream of the selective catalytic reduction system at an injection rate that is based on the measured level of NOx gases. Optionally provided is a further downstream selective catalytic reduction system (126) comprising a second diesel exhaust fluid injector (124) and measuring a level of NOx gases (at 128). The controlling method determines ammonia slip by comparing the upstream and downstream measured level of NOx gases and adjusts the DEF-rate by the diesel exhaust fluid injectors (110,124) accordingly.