An estimate of diesel high-efficiency clean combustion impacts on FTP-75 aftertreatment requirements

A modified Mercedes 1.7-liter, direct-injection diesel engine was operated in both normal and high-efficiency clean combustion (HECC) combustion modes. Four steady-state engine operating points that were previously identified by the Ad-hoc fuels working group were used as test points to allow estimation of the hot-start FTP-75 emissions levels in both normal and HECC combustion modes. The results indicate that operation in HECC modes generally produce reductions in NO_X and PM emissions at the expense of CO, NMHC, and H₂CO emissions. The FTP emissions estimates indicate that aftertreatment requirements for NO_X are reduced, while those for PM may not be impacted. Cycle-average aftertreatment requirements for CO, NMHC, and H₂CO may be challenging, especially at the lowest temperature conditions.