## 4 Results
### RDE Tests
Figure 7 and Table 6 show the specific emissions in grams per kilometer of NO\({}_{\rm X}\), CO, THC, and CO\({}_{2}\). In case of PM emissions, the particles could not be registered along the entire tests, due to the required purge of the opacimeter. Therefore, global emissions have not been plotted in Figure 7. These specific emissions for three periods of RDE 1 are in Section 4.2 for the sake of completeness. Tests were performed without urea injection so that NO\({}_{\rm X}\) emissions were above the regulatory limit. On the other hand, THC and CO fulfill the type-approval limits after being oxidized in the DOC. Figure 7 shows a significant dispersion between pollutant emissions. In the case of NO\({}_{\rm X}\) emissions, leaving RDE 6 aside (the driver behavior was modified), the differences reached up to 17.39% in an urban zone, 30.88% in the rural zone, and 27.10% in the motorway. The total specific emissions showed the maximum difference of 12.74% between RDEs 2 and 5. THC and CO strongly depended on the engine and aftertreatment temperatures. RDEs 5 and 6, which were the cycles less loaded, showed the lowest HC emission. These emissions were produced due to incomplete combustion when the engine was yet cold and during phases with high load or high EGR rates where lambda was even below 1. RDE 2 produced the highest CO emissions, which was mainly due to the large contribution in the \begin{table}
\begin{tabular}{c c c c c} \hline  & **NO\({}_{\rm X}\)** & **THC** & **CO** & **CO\({}_{2}\)** \\ \hline  & & & [g/km] & \\ \hline RDE 1 & 0.4378 & 0.0170 & 0.0738 & 175.28 \\ RDE 2 & 0.4778 & 0.0217 & 0.1268 & 174.29 \\ RDE 3 & 0.4508 & 0.0234 & 0.0978 & 164.15 \\ RDE 4 & 0.4384 & 0.0174 & 0.0685 & 169.73 \\ RDE 5 & 0.4241 & 0.0142 & 0.0515 & 162.27 \\ RDE 6 & 0.2799 & 0.0110 & 0.0501 & 147.34 \\ \hline \end{tabular}
\end{table} 
Table 6: RDE pollutants emissions per kilometer. Figure 7: NO\({}_{\rm X}\) (a), CO (b), THC (c) and CO\({}_{2}\) (d) pollutant emissions. urban area. This cycle had the lowest urban and total distances, which increased specific emissions per kilometer due to the higher impact of the engine warm-up phase. The other cycles did not show significant differences. In the case of CO2 emissions, there were also big differences, with RDEs 1 and 2 producing the highest emissions. The biggest difference between RDEs 3 and 4 was the average vehicle speed reduction, which implied an increase in fuel consumption. RDE 5 resulted in the lowest CO2 emission among the cycles with the same driver behavior (RDE 1 to RDE 5). RDE 1 was the most representative of real driving since it was directly extracted from a cycle performed on road. Comparing RDEs 1 and 2, where the results are similar, contributes to stating that a WLTC presents similar dynamic conditions as an RDE cycle since CO2 and NOX emissions showed analogous values. The comparison between RDEs 5 and 6 led to characterize the effect of the different driver behavior in the same trip and vehicle speed profile. RDE 6 NOX emissions were reduced by 34% compared to RDE 5. In the case of THC and CO, similar drawdowns were obtained whilst CO2 emissions were decreased by 9.2%. The required engine power to reach a certain vehicle speed in a cycle is obtained from the engine speed and torque. Since the engine speed was reduced in the case of the RDE 6 by varying the shifting procedure, the torque was increased. Figure 8 shows the effective engine torque as a function of engine speed for RDEs 5 and 6. RDE 6 dots are located closer to the top left corner (high torque and low engine speed). According to the driver behavior, in the case of RDE 5, the engine speed reached higher values while more loaded conditions were characteristic in RDE 6. Figure 9 shows three different fractions of RDE 5 and 6 cycles during urban, rural, and motorway driving, where the differences in CO2 and NOX emissions can be observed. Figure 8: RDE 5 and RDE 6 engine map comparison.