Euro 6 Diesel Passenger Cars’ Emissions Field Tests: Project Final Report

According to the measurements it can be stated with respect to NOx emissions that there are large differences in NOx emissions within the Euro 6b cars. One tested car showed high NOx emissions on the chassis dynamometer and in the on-road tests with the conformity factor (CF) varying between 3.3…5.2. A second car was able to provide NOx, CO and PN emissions fulfilling the Euro 6d-TEMP RDE requirements with a conformity factor around 1.8. A third Euro 6b car equipped with selective catalytic reduction system (SCR) was, after the update in engine control unit software, able to provide really low on-road NOx emissions with a conformity factor varying between 0.2…0.9 depending on the test route. The only Euro 6d-TEMP car resulted low NOx emissions on the chassis dynamometer independent of the test cycle. In on-road measurements, the conformity factor varied between 0.5…2.0 depending on the test route. Near-zero ambient temperature was not found to increase the NOx, CO and PN emissions in tests on the RDE-route. Furthermore, one Euro 6b car showed a slight increase in CO2 emissions, when tested close to zero ambient temperature compared to testing around 15 °C. Day-to-day NOx concentration monitoring showed that Euro 6b cars equipped with a single lean NOx trap (LNT) did emit relatively constant NOx emissions and did not suffer from cold ambient conditions. On the other hand, a Euro 6b car with SCR showed 2…3 times higher NOx emissions at below 0 °C compared to in summer conditions. A Euro 6d-TEMP car with dual LNT showed, on average, low NOx concentration, but with high fluctuation and high peaks. Two different diesel fuels were used in the Euro 6 RDE route. One fulfilling the EN590 diesel fuel standard and one using WWFC cat 5 diesel. None of the cars tested showed any observable difference between the emissions. There was no clear trend identified in respect of measurement accuracy in favor of either of the fuels.