## 4 Results
### Principle of Measurement  
Figure 4 plots the results for the G-PFI #1 vehicle at two different laboratories. The tests were conducted with a time difference of 1 year and different settings at the chassis dynamometer, so the absolute levels are not directly comparable. Nevertheless, in both cases the wet measurements (PEMS A, left panel or FTIR right panel) are higher than the wet corrected results according to the RDE equation (Lab 1 and PEMS B left panel, Lab 2 and PEMS B, right panel). The differences become smaller when the correction based on H\({}_{2}\)O is used (Lab 1 or 2 wet corr. H\({}_{2}\)O). Together with results in Figure 3, this confirms that the cold start differences discussed so far are neither company, nor instrument, nor laboratory dependent, but have to do with the principle of the measurement (direct wet measurement or corrected). The differences between FTIR and heated NDIR are out of the scope of this study. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Vehicle**} & **Start** & **Start** & **Start** & **Dev** & **Rest** & **Rest** & **Dev** \\  & **Time (s)** & \(\mathbf{K_{d\text{-}w,H2O}}\) & \(\mathbf{K_{d\text{-}w,RDE}}\) & **(\%)** & \(\mathbf{K_{d\text{-}w,H2O}}\) & **(\%)** \\ \hline Diesel \#1 & 35 & 0.99 & 0.94 & \(-\)5.0\% & 0.94 & 0.95 & +0.9\% \\ Diesel \#2 & 45 & 0.99 & 0.96 & \(-\)3.7\% & 0.94 & 0.95 & +1.0\% \\ CNG \#1 & 200 & 0.93 & 0.82 & \(-\)12.0\% & 0.80 & 0.82 & +3.1\% \\ CNG \#2 & 135 & 0.88 & 0.82 & \(-\)7.1\% & 0.80 & 0.82 & +1.9\% \\ G-PFI \#1 & 230 & 0.94 & 0.87 & \(-\)7.6\% & 0.86 & 0.88 & +2.0\% \\ G-PFI \#2 & 160 & 0.95 & 0.88 & \(-\)7.4\% & 0.87 & 0.89 & +2.3\% \\ G-DI & 600 & 0.92 & 0.88 & \(-\)4.6\% & 0.85 & 0.87 & +2.6\% \\ Motorcycle & 100 & 0.92 & 0.87 & \(-\)5.2\% & 0.86 & 0.87 & +1.5\% \\ Moped & 140 & 0.94 & 0.88 & \(-\)6.0\% & 0.86 & 0.88 & +2.7\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Dry-wet conversion factors \(K_{d\text{-}w}\) for the starting condensation period (“Start”) and the rest cycle (“Rest”) calculated before and after the “Start time” respectively. “Dev” stands for the relative deviation between the \(K_{d\text{-}w,H2O}\) and the \(K_{d\text{-}w,RDE}\). Vehicles and acronyms as in Table 2.  
Figure 4: Comparison of different analyzers during a cold start WLTC of the Gasoline Port Fuel Injection (G-PFI) #1 vehicle. Left panel: Laboratory 1, portable emissions measurement system (PEMS) A, and PEMS B. Right panel: Laboratory 2, PEMS B, and FTIR. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Vehicle**} & **Start** & **FTIR Start** & **Lab with** & **Lab with** & **FTIR Rest** & **Lab with** & **Lab with** \\  & **Time (s)** & **CO\({}_{2}\) (\%)** & **K\({}_{d-u,RDE}\)** & **K\({}_{d-u,H2O}\)** & **CO\({}_{2}\) (\%)** & **K\({}_{d-u,RDE}\)** & **K\({}_{d-u,H2O}\)** \\ \hline Diesel \#1 & 35 & 5.53 & \(-\)8.4\% & \(-\)2.0\% & 4.85 & \(-\)1.4\% & \(-\)1.8\% \\ Diesel \#2 & 45 & 3.79 & \(-\)5.4\% & \(+\)0.4\% & 5.00 & \(-\)0.3\% & \(-\)0.5\% \\ CNG \#1 & 200 & 10.01 & \(-\)9.7\% & \(-\)0.5\% & 9.02 & \(-\)1.2\% & \(-\)0.1\% \\ CNG \#2 & 135 & 9.38 & \(-\)6.3\% & \(-\)1.5\% & 9.01 & \(+\)0.3\% & \(+\)3.0\% \\ G-PFI \#1 & 230 & 13.04 & \(-\)5.3\% & \(-\)0.2\% & 12.05 & \(-\)0.2\% & \(-\)1.4\% \\ G-PFI \#2 & 160 & 13.31 & \(-\)7.3\% & \(+\)0.6\% & 11.79 & \(+\)0.7\% & \(-\)1.5\% \\ G-DI & 600 & 13.22 & \(-\)9.3\% & \(-\)1.0\% & 12.77 & \(-\)1.2\% & \(-\)2.2\% \\ Motorcycle & 100 & 13.11 & \(-\)6.6\% & \(-\)0.7\% & 12.97 & \(-\)1.7\% & \(-\)1.0\% \\ Moped & 140 & 12.57 & \(-\)4.6\% & \(+\)1.9\% & 11.84 & \(+\)1.8\% & \(+\)1.4\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mean CO\({}_{2}\) concentration measurements (%) measured with the FTIR for the starting condensation period of the cycle and the rest of the cycle. The laboratory to the FTIR differences are given using the two conversion factors (real driving emissions (RDE) or H\({}_{2}\)O).