An Unconventional Application of a HC Trap to Meet SULEV20

Passive hydrocarbon traps (“HCT”) are limited in performance when installed in an oxygen deprived location, such as an underfloor that is downstream of a CC TWC. An OEM 1.0L close-coupled converter in a 1.4L turbo hybrid PZEV calibrated vehicle was replaced with a 1.24L HC trap. The HC trap consisted of a zeolytic storage layer beneath a Pd/Rh containing three-way catalyst layer. The UF converter was upgraded with a newer TWC technology. The HC trap and UF TWC were engine aged to simulate 150,000 miles, or full useful life conditions. Criteria for accelerated engine aging of the HC trap were selected based on the vehicle application’s peak operating bed temperatures in the field. Vehicle FTP and US-06 tests were conducted on an all-wheel drive dyno which facilitated normal hybrid powertrain operation. A SULEV20 engineering target for FTP nMHC+NOx emissions was met with the full useful life aged CC HC Trap (“HCT”) system, using a PGM amount that was lower than the OEM design. The aged experimental system resulted in nMHC and NOx emissions of 5 and 10 mg’s/mile, respectively. CO emissions were well below the 1.0 g/mi LEV-3 SULEV20 limit. US-06 nMHC + NOx emissions were below 10 mg/mile. A high level of HC performance for the CC HC trap was achieved due to oxygen availability during the desorption phase vs the case where the trap is installed downstream of a TWC in a secondary position.