Various embodiments of an apparatus, system, and method are disclosed for controlling NOx conversion in a selective catalytic reduction (SCR) system. According to one representative embodiment, an apparatus includes a duty cycle factor module and a NOx conversion mode selection module. The duty cycle factor module is configured to determine a duty cycle factor of an internal combustion engine where the duty cycle factor represents predicted driving conditions of a vehicle in which the internal combustion engine is housed. The NOx conversion mode selection module is configured to command NOx conversion in the SCR system according to a first NOx conversion mode if the duty cycle factor is within a duty cycle factor range and according to a second NOx conversion mode if the duty cycle factor is not within the duty cycle factor range.