White paper

Beyond NOx: Emissions of unregulated pollutants from a modern gasoline car

For this study, a C-segment passenger vehicle, equipped with a gasoline direct injection engine and compliant with the Euro 6c standard, was tested on the chassis dynamometer over the regulatory NEDC and WLTC cycles, and over two RDE-like cycles. The tests were performed at different ambient conditions and with both cold and warm engines.

Key findings of the tests include:

  • The vehicle exhibited good emissions performance for regulated pollutants and were below Euro 6 standards, with the exception of the cold-start test. Under low temperatures, the limits were exceeded for hydrocarbons and particulate matter.
  • If solid particles in the unregulated size range had been accounted for, the total emissions of solid PN would have been up to 114% higher. Accounting for volatile particles would further increase PN emissions by up to 78%.
  • Ammonia emissions amounted to half the mass NOx emissions and were 10% higher than the molar NOx emissions. Formaldehyde, methane, and nitrous oxide were also found in non-negligible amounts.

These findings suggest that policymakers should consider:

  • Extending the low temperature test (type 6 test) at -7°C to include all regulated pollutants;
  • Reducing the size threshold for solid particle counting and consider the inclusion of volatile particles in the measurement methodology;
  • Introducing technology- and application-neutral limits for vehicular ammonia emissions;
  • Establishing technology- and application-neutral limits for methane and nitrous oxide emissions; and
  • Introducing technology- and application-neutral limits for vehicular formaldehyde.