Cold-start and low-temperature emissions challenges
Robert McCabe, Ford Motor Company
Cold-start emissions and fast catalyst light-off remain the greatest challenge to compliance with emission phase-in plans. The potential introduction of lower temperature combustion systems can be expected to further aggravate the cold-start challenge in the future. For diesel engines, even warmed-up exhaust temperatures are marginal for achieving the most stringent emission standards. Moreover, the recent increase in use of technologies such as direct injection and turbochargers can increase cold-start emissions of species such as hydrocarbons and particulate emissions, while adding turbo thermal lag to catalyst warm-up. I will review the current status of cold-start and low-temperature emission challenges for both gasoline and diesel engines, summarize our understanding of factors that limit low-temperature catalyst performance, and discuss technologies under consideration for enhancing low-temperature catalyst performance. While hardware-intensive solutions such as electrically heated catalysts and bypass hydrocarbon traps always remain an option, a stand-alone low-temperature light-off catalyst remains elusive. 40 years of exhaust catalyst research and development still results in three-way catalysts that light off above 200 °C.