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. Next, a clean base exhaust gas generator was examined. The purpose of using clean exhaust gas as base gas is to simulate thermal conditions and H2O and CO2 concentrations, which influence gas density, viscosity and infrared absorption. However, emission changes in exhaust gasses from actual vehicles affect the verification of measurement accuracy. Several emission tests were conducted on SULEV vehicles with new fully warmed catalysts, confirming emission stability and that those exhaust gases satisfied desired levels.
This paper explains not only the development of the SULEV exhaust emission simulator described above, such as its design and evaluation results, but also the results and prospects of its use verifying the precision of low emission measurement systems.