## 3 Results
### BC Emission According to Engine Characteristics and Tightening of Regulations  
BC emission from vehicles is related to various parameters; engine technology, adoption of aftertreatment like DPF, driving conditions such as a temperature, humidity, acceleration, and deceleration [24,25]. Therefore, in order to understand the characteristics of BC emission, we classified gasoline vehicles according to the engine technology of GDI and MPI, and the degree of aging of MPI vehicles, and diesel vehicles were classified by emission certification mode. Comparing the difference in BC emission for gasoline vehicles with GDI engines and the PM regulation of 0.004 g km\({}^{-1}\) after 2014, in the heated state, G\({}_{\text{bCDI}}\)#1 vehicle (before PM regulation) showed an emission of 0.2-1.03 mg km\({}^{-1}\), and G\({}_{\text{aCDI}}\)#2, 3 vehicles (after PM regulation) showed an emission of 0.038-0.2 mg km\({}^{-1}\), which confirmed that in the preheated state. The GDI vehicle before the PM regulation emitted more BC by approximately five times compared with that after the PM regulation (Figure 6a and Table 4). In the CVS-75 mode, including both the cold start state and before the preheating state, BC emission was higher in G\({}_{\text{bCDI}}\)#5 (0.44 mg km\({}^{-1}\)) than in G\({}_{\text{aCDI}}\)#6 (0.16 mg km\({}^{-1}\)) by about 2.8 times. For MPI vehicles without the PM regulation, BC emissions from vehicles in the NIER mode, in the heated state, were lower by 23 times at the minimum and 25 times at the maximum than those of the GDI vehicles. However, in the CVS-75 mode, which includes cold start, the emission was lower by 2-3 times than that of GDI vehicles. These results showed that driving in sufficient preheating conditions on MPI vehicles emitted low BC emission, but the emission was higher on cold start and before the preheating condition (Figure 6b and Table 5). Among gasoline vehicles, the emission difference between GDI and MPI vehicles is believed to be attributable to the increased PM emissions associated with the GDI method and the increased incomplete combustion associated with the MPI method, leading to increased BC emissions [26]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & \multicolumn{4}{c}{**(Unit: mg km\({}^{-1}\))**} \\ \hline \multirow{2}{*}{**Mode**} & **Avg. Speed** & \multirow{2}{*}{**GDI**} & **GDI** & **GDI** \\  & **(km h\({}^{-1}\))** & & **(Before PM Reg.)** & **(After PM Reg.)** & **MPI** \\ \hline NIER-01 & 4.7 & 1.03 \(\pm\) 0.56 & 0.2 \(\pm\) 0.083 & 0.0036 \(\pm\) 0.0008 \\ NIER-05 & 17.3 & 0.53 \(\pm\) 0.25 & 0.081 \(\pm\) 0.0004 & 0.0016 \(\pm\) 0.0003 \\ NIER-09 & 34.1 & 0.27 \(\pm\) 0.12 & 0.038 \(\pm\) 0.002 & 0.0016 \(\pm\) 0.0006 \\ NIER-12 & 65.4 & 0.2 \(\pm\) 0.05 & 0.045 \(\pm\) 0.019 & 0.0014 \(\pm\) 0.0007 \\ NIER-14 & 97.3 & 0.64 \(\pm\) 0.21 & 0.053 \(\pm\) 0.026 & 0.0018 \(\pm\) 0.0008 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: BC Emission from gasoline vehicles with different types of engines and PM regulations in the NIER mode. \begin{table}
\begin{tabular}{c c c} \hline \hline  & & **(Unit: mg km\({}^{-1}\))** \\ \hline \multirow{2}{*}{**Mode**} & **Fuel** & **Phase** & **BC** \\ \multirow{4}{*}{CVS-75} & \multirow{4}{*}{Gasoline} & Phase 1 & 0.3 \(\pm\) 0.014 \\  & & Phase 2 & 0.15 \(\pm\) 0.011 \\  & & Phase 3 & 0.093 \(\pm\) 0.0004 \\  & & All Phase & 0.16 \(\pm\) 0.003 \\ \cline{2-3}  & \multirow{4}{*}{LPG (\({}^{\text{a}}\))} & Phase 1 & 0.014 \\  & & Phase 2 & 0.0033 \\  & & Phase 3 & 0.014 \\  & & All Phase & 0.0009 \\ \hline \multirow{2}{*}{NEDC} & \multirow{2}{*}{Diesel} & Phase 1 & 0.04 \(\pm\) 0.0005 \\  & & Phase 2 & 0.047 \(\pm\) 0.001 \\ \cline{1-1}  & & All Phase & 0.045 \(\pm\) 0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The results of BC emissions in CVS-75 mode for GDI gasoline and LPG vehicles, NEDC mode for diesel vehicle corresponding to emission certification mode in Korea.