The second-by-second exhaust port and catalyst bed temperature profiles, measured with K-type thermocouples, are shown in Fig. 4. The vehicle preconditioning procedure of the NIER mode was carried out following the HWFET mode and for sustaining fully warmed-up conditions of the UCC, the exhaust system temperatures at the mode starting phase were over 400 °C, which are an advantage for higher catalyst efficiency. Similar trends as shown in the vehicle parameters are observed in the exhaust system temperatures. Operation of the vehicle at higher speeds resulted in higher exhaust gas and catalyst bed temperature.