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A two-brick gasoline engine aftertreatment system with advanced washcoat technology was developed for LEV2 PZEV2 legislation, and its application to the upcoming LEV3 SULEV30 emission standard was demonstrated. The system was comprised of 1) a palladium only catalyst in the close coupled position with improved catalytic performance and high phosphorus poisoning resistance compared with 09MY technology, and 2) an underfloor palladium rhodium catalyst technology in which the nitric oxides (NOx) reduction activity was enhanced by preventing the deactivation of rhodium under rich conditions. As a result, the palladium only + palladium rhodium catalysts system met the LEV2 PZEV standard with three quarters of the PGM and half the rhodium of the system used on the Honda 09MY Accord vehicle. The system was also demonstrated to meet the LEV3 SULEV30 standard with some margin.

Recently, automotive emission regulations are being further tightened, such as the Tier III/LEV III in the U.S. As a result, reducing cost of after-treatment systems to meet these strict regulations has become an urgent issue, and then the demand for high-precision air-fuel ratio (A/F) control which can achieve this cost reduction is high [1]. On the other hand, in order to meet rapidly changing market needs, it is becoming difficult to keep enough development periods that enable sufficient calibration by trial-and-error, such as feedback-gain calibration. This leads to an increase in three-way catalytic converter costs in some cases. For these reasons, it is necessary to construct control system that can make full use of hardware capabilities, can shorten development periods regardless of the skill level of engineers.