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With the support of Horiba and Horiba STEC, Toyota Motor Corporation has developed an exhaust emissions simulator to verify the accuracy of extremely low emissions measurement systems. It can reliably verify the accuracy (correlation) of each SULEV emission measurement system to within 5% under actual conditions. The simulator's method of simulating SULEV gasoline engine cold-start emissions is to inject bottled gases with known concentrations of each emission constituent to the base gas, which is clean exhaust gas from a SULEV vehicle with new fully warmed catalysts. First, the frequencies and dynamic ranges of the SULEV cold-start emissions were analyzed and the method of 2 injecting the bottled gases was considered based on the results of that analysis. A high level of repeatability and accuracy was attained for all injection flow ranges in the SULEV cold-start emission simulation by switching between high-response digital Mass Flow Controllers (MFCs) of different full scales.

Conventional constant volume sampling (CVS) is well known as a precision emissions measurement method, even though the concentrations of THC, NOX, CO and CH₄ emitted from vehicles are getting lower by improvement of emissions control devices. Recently, fuel economy requirements have increased in many regions. Hybrid electric vehicle (HEV), or plug-in hybrid electric vehicle (PHEV), is one of the solutions for fuel economy improvement. HEVs and PHEVs have an all-electric range in which the internal combustion engines (ICEs) are completely shut down. This operation results in a high dilution factor (DF) and low concentrations of gaseous components, including CO₂, in the CVS system. Such dilution conditions directly cause an increase of numerical error for DF and an analysis error for gaseous components. Furthermore, a small amount of air flow across exhaust catalysts, drawn by slightly negative tailpipe pressure generated by the CVS during ICE shutdown may influence emission results.