Effect of B20 and Low Aromatic Diesel on Transit Bus NOx Emissions Over Driving Cycles with a Range of Kinetic Intensity

Research output: Contribution to conferencePaper


Oxides of nitrogen (NOx) emissions for transit buses for up to five different fuels and three standard transit duty cycles were compared to establish whether there is a real-world biodiesel NOx increase for transit bus duty cycles and engine calibrations. Six buses representing the majority of the current national transit fleet and including hybrid and selective catalyst reduction systems weretested on a heavy-duty chassis dynamometer with certification diesel, certification B20 blend, low aromatic (California Air Resources Board) diesel, low aromatic B20 blend, and B100 fuels over the Manhattan, Orange County and UDDS test cycles. Engine emissions certification level had the dominant effect on NOx; kinetic intensity was the secondary driving factor. The biodiesel effect on NOxemissions was not statistically significant for most buses and duty cycles for blends with certification diesel, except for a 2008 model year bus. CARB fuel had many more instances of a statistically significant effect of reducing NOx. SCR systems proved effective at reducing NOx to near the detection limit on all duty cycles and fuels, including B100. While offering a fuel economy benefit, ahybrid system significantly increased NOx emissions over a same year bus with a conventional drivetrain and the same engine.
Original languageAmerican English
Number of pages15
StatePublished - 2012
Event2012 SAE Commercial Vehicle Engineering Congress - Rosemont, Illinois
Duration: 2 Oct 20123 Oct 2012


Conference2012 SAE Commercial Vehicle Engineering Congress
CityRosemont, Illinois

Bibliographical note

Posted with permission

NREL Publication Number

  • NREL/CP-5400-55672


  • biodiesel
  • buses
  • drive cycles
  • emissions
  • hybrid
  • NOx
  • transit


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