Using on-board emission tests from portable emission measurement systems (PEMS) is becoming more and more a common approach for real world emission testing of passenger cars (PC), light commercial vehicles (LCV) and heavy duty vehicles (HDV). The advantages against chassis dyno tests are the high robustness to obtain unbiased emission levels and to cover a lot of real world driving situations. Disadvantages for the use in emission modelling are the high influence of the route, the driver, traffic conditions and ambient temperature on the resulting emissions. Consequently test results show a high variability for single vehicles and can hardly be used directly to obtain emission factors. Figure 1 shows as example test data from one EU 6 diesel car in 25 PEMS trips and in New European Drive Cycle (NEDC), Worldwide Harmonized Light-Duty Vehicles Test Procedure (WLTP) and European Research Group on Mobile Emission Sources cycle (ERMES) as chassis dyno tests. NOx measured in the PEMS tests had a factor of 7 between lowest and highest test value. Obviously ambient temperature, engine load and cycle dynamics have high influence on the measured emissions and should be considered in a systematic way to elaborate reliable fleet emission values.
Keywords: CO2 interpolation method, engine map, emission, simulation, PEMS.