## 3 Results
### BC Emission According to Engine Characteristics and Tightening of Regulations
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & & & **(Unit: mg km\({}^{-1}\))** \\ \hline
**Mode** & **Vehicle** & **Phase** & **PM** & **BC** \\ \hline \multirow{8}{*}{CVS-75} & \multirow{4}{*}{\(\text{G}_{\text{b,GDI}}\)#5} & Phase 1 & 8.38 \(\pm\) 1.34 & 0.49 \(\pm\) 0.096 \\  & & Phase 2 & 0.41 \(\pm\) 0.001 & 0.38 \(\pm\) 0.01 \\  & & Phase 3 & 7.77 \(\pm\) 1.83 & 0.50 \(\pm\) 0.023 \\  & & All Phase & 4.5 \(\pm\) 0.028 & 0.44 \(\pm\) 0.018 \\ \cline{2-5}  & \multirow{4}{*}{\(\text{G}_{\text{a,GDI}}\)#6} & Phase 1 & 4.51 \(\pm\) 1.3 & 0.3 \(\pm\) 0.014 \\  & & Phase 2 & 1.42 \(\pm\) 0.31 & 0.15 \(\pm\) 0.011 \\  & & Phase 3 & 1.64 \(\pm\) 0.82 & 0.093 \(\pm\) 0.0004 \\  & & All Phase & 2.33 \(\pm\) 0.72 & 0.16 \(\pm\) 0.003 \\ \hline \multirow{8}{*}{CVS-75} & \multirow{4}{*}{\(\text{G}_{\text{MPI}}\)#7} & Phase 1 & 2.55 \(\pm\) 0.49 & 0.15 \(\pm\) 0.079 \\  & & Phase 2 & 0.31 \(\pm\) 0.10 & 0.045 \(\pm\) 0.006 \\ \cline{1-1}  & & Phase 3 & 0.63 \(\pm\) 0.33 & 0.069 \(\pm\) 0.02 \\ \cline{1-1}  & & All Phase & 0.95 \(\pm\) 0.27 & 0.072 \(\pm\) 0.025 \\ \hline \multirow{8}{*}{\(\text{G}_{\text{MPI}}\)#8} & Phase 1 & 0.11 \(\pm\) 0.037 & 0.14 \(\pm\) 0.013 \\ \cline{1-1}  & & Phase 2 & 0.034 \(\pm\) 0.034 & 0.018 \(\pm\) 0.005 \\ \cline{1-1}  & & Phase 3 & 0.074 \(\pm\) 0.00002 & 0.07 \(\pm\) 0.012 \\ \cline{1-1}  & & All Phase & 0.067 \(\pm\) 0.028 & 0.058 \(\pm\) 0.009 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: PM and BC emissions from gasoline vehicles with different types of engines and PM regulations in the CVS-75 mode. Figure 6: BC emission from gasoline vehicles according to different types of engines and PM regulations. (**a**) the result of vehicles tested in 5 different NIER modes, (**b**) the comparison of BC emission from different fuel types in the CVS-75 mode. BC is a component of PM and to identify the BC emission in PM according to the implementation of the PM regulation, the value was represented as a ratio using the emissions of PM and BC measured in gasoline vehicles (Figure 7). The BC/PM ratio of GDI vehicles changed from 9.7% to 7% before and after the PM regulation application, indicating that the regulation decreased BC emission by approximately 2%. The BC/PM ratio was 7.6% for MPI vehicles of the model years 2001-2005 and 86% for vehicles of model years 2009-2012 confirming that PM emissions other than BC decreased in recent vehicles compared to older vehicles. Figure 8 shows the results of BC emissions following the tightening of regulations on diesel vehicles; the results according to driving speed are shown for EURO 3, 5, and 6 vehicles (Figure 8a and Table 6) in NIER modes, and BC emissions are shown for EURO 3, 4, 5, and 6 vehicles (Figure 8b and Table 7). As for EURO 3, CVS-75, a regulation mode for emissions in those days, was applied and for EURO 4 to 6, NEDC, emission certification mode of the corresponding regulation, was applied in CVS-75 and NEDC. In the NIER mode, driven in the preheated state, the BC emission of EURO 3 vehicles was measured to be 6.21-24.54 mg km\({}^{-1}\), which was found to be 2000 times higher than that of EURO 5 and 6 vehicles (0.0005-0.0093 mg km\({}^{-1}\)). In the NEDC mode with cold start, as in the NIER mode, EURO 3 vehicles without DPF (66.29 mg km\({}^{-1}\)) showed the highest emission, followed by EURO 4 (0.1 mg km\({}^{-1}\)), EURO 5 (0.084 mg km\({}^{-1}\)), and EURO 6 (0.044 mg km\({}^{-1}\)). EURO 3 diesel vehicles with the highest emission are not equipped with DPF, an aftertreatment device that reduces PM emission, commonly used in vehicles manufactured after EURO 4. For this reason, the installation of DPF in diesel vehicles is believed to be effective in reducing BC emission. In addition, the BC/PM emission ratio of diesel vehicles was the highest with EURO 3 vehicles at 74.4%, followed by EURO 4 (63.1%), EURO 5 (18.6%), and EURO 6 (4.4%), confirming that the BC ratio also decreased with the tightening of PM regulation (Figure 9). Figure 7: BC/PM ratio of gasoline vehicles. (**a**) GDI vehicle before PM regulation.