## 3 Materials and Methods  
To evaluate the influence of the EGH in NOx emissions reduction, a certified bench for Heavy Duty vehicles was used. The experiment series were held in EVARM S.L. facilities which had a certified test bench for testing HDVs (Powerdyno R200/1, Maha, Bescano, Spain) was used to put the vehicle in real operating conditions. This equipment was also used to capture the FTPP, NOx after and before the ATS, and exhaust temperatures from the ECU. The measurement of NOx emissions was done with a MIAC G4.0 located at the end of the exhaust pipe. This device presents a measure range from 0 to +5000 ppm, an accuracy of \(\pm\)5% of mv (+100 to +2000 ppm) and \(\pm\)5 ppm (0 to +99.9 ppm) with a resolution of 0.1 ppm (0 to +500 ppm). A Power Explorer PX5 power meter (Dranetz, Nurnberg, Germany) was used to measure the EGH power consumption with the following specifications: voltage measuring range from 1-600 Vrms with 0.1% rdg (reading) + 0.05% FS (full scale), 256 samples/cycle, 16 bit ADC; current measuring range from 1-6000 Arms with 0.1% rdg + CTs (4), 256 samples/cycle, 16 bit ADC. Exhaust temperatures were recorded with a National Instruments DAQ with one NI 9211 acquisition module. This device presents a maximum measure error of 2.2 \({}^{\circ}\)C (0-400 \({}^{\circ}\)C) with a measurement sensitivity \(<\) 0.07 \({}^{\circ}\)C. All temperature probes used were type K thermocouples.  
The method used to calculate absolute uncertainty values depends on the equipment accuracy. These parameters are obtained from datasheet provided by different manufacturers as exposed before. Thus, temperature and NOx measurement standard uncertainties have been calculated. Voltage and current (used to calculate EGH power consumption) are separately obtained and its uncertainties also calculated using the same method. As EGH power is an indirect parameter, its uncertainty is the result of both electrical magnitudes as it depends on these parameters [22].  
In this study, a Heavy-Duty Vehicle Euro VI TGX 18.480 Efficient Line 2 from MAN was used to carry out the tests. Its specifications are summarized in Table 1.  
\begin{table}
\begin{tabular}{c c} \hline \hline Parameter & Value \\ \hline \hline Maker & MAN \\ \hline Model & TGX 18.480 Efficient Line 2 \\ \hline \hline Gearbox & Automatic (12 gears) \\ \hline Max. rated power & 353 kW (at 1800 rpm) \\ \hline Max. rated power & 1500 Nm (at 930–1400 rpm) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Main specifications of tested vehicle.  
Figure 4 shows the rolling bench with the vehicle tested. All tests were carried out using the same load.  
Three different engine regimes were selected to conduct the study: 1000 rpm (\(\approx\)55 km/h), 1250 rpm (\(\approx\)65 km/h) and 1500 rpm (\(\approx\)80 km/h). All these regimes, shown in Figure 5, can be found in a typical daily drive. The suitable gear to obtain all range of full throttle pedal position (FTPP) values was the eleventh. During all tests, the engine temperature stayed below 90 \({}^{\circ}\)C to keep the same engine conditions. Before each test, the vehicle was warmed up at idle for 20 min. NOx emissions were captured along the tests. Maximum FTPP tested is 90% to assure that can be reached equally in all conditions. In all tests, the setpoint temperature of the EGH was set to 300 \({}^{\circ}\)C to ensure that the exhaust gas temperature at SCR inlet was above the SCR light-off temperature of 220 \({}^{\circ}\)C.