Measurement of real world emissions from passenger cars and HDVs

Project duration: 2019 - 2021

Funded by: Umweltbundesamt Deutschland

Project team: Weller, Lipp, Landl, Matzer, Hausberger

From 2018 to 2021, a total of 48 passenger cars, 10 light commercial vehicles and 30 heavy duty vehicles were measured on the chassis dynamometer and on-board at the Institute on behalf of the German Federal Environment Agency. In addition to the WLTC, real world cycles were also run on the test bench. In the process, relevant non-limited exhaust gas components were also measured by means of FTIR. In the on-board tests, different driving styles and loads were tested. The main objective was to generate data on the real emission behaviour of EURO 6/VI vehicles, which can then also be used in the Handbook on Emission Factors (www.hbefa.net). Therefore, not all tests are valid RDE tests. In the following figure, the box shows the range from 1st to 3rd quartile and the cross shows the mean value. Points show outliers, which are partly due to filter regeneration, but also to high mileage and declining exhaust gas cleaning of individual cars.

Figure 1: Measurement results of the passenger car PEMS tests related to the WLTC limits
(CO2: 95; CO: 0,5; NOx: 0,08; PN: 6E+11 #/km)

Overall, the picture for EURO 6d-temp and 6d is very positive. With a few exceptions, all tested passenger cars are below the limit value for WLTP. However, only 2 diesel cars were measured for EURO 6d, as this emission class was not available on the market until very late in the project.

As expected, CO and HC emissions from heavy-duty vehicles (HDVs) were very low. Particulate emissions were also well below the limit value, with the exception of one truck that was measured with 370,000 km on the odometer and presumably had a defective filter. The defective DPF caused the particulate emissions to increase up to 65 times the limit value, so that this measurement data is not shown in the following graph. NOx emissions were below the limit value on average for all SNFs that were measured with rather low mileage. EURO VI D certified SNFs were significantly lower than EURO VI A to C certified SNFs. With increasing mileage, the emission levels tended to increase. Chemical and thermal ageing of the DOC (diesel oxidation catalyst) and SCR (NOx catalyst) cause NOx conversion to drop and CO and HC emissions to rise. The on-board diagnostics did not indicate any errors in the tests, but the OBD limits were usually not exceeded.

Figure 2: Measurement results of the SNF PEMS and roller tests related to the WHTC limits
(CO: 4 g/kWh, HC: 0,16 g/kWh, NOx: 0,46 g/kWh, PN: 6,0 E+11 #/kWh)

The measurements indicate for the future massive reductions in pollutant loads from traffic, as the EURO 6 generation is significantly cleaner than its predecessors. Increases in emissions over the service life as well as higher NOx levels in low-load operation (not shown here) should be eliminated with EURO 7.