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On-Board Diagnostics for emissions-related components require the monitoring of the catalytic converter performance. Currently, the dual Exhaust Gas Oxygen (EGO) sensor method is the only proven method for monitoring the catalyst performance for hydrocarbons (HC). The premise for using the dual oxygen sensor method is that a catalyst with good oxygen storage capacity (OSC) will perform better than a catalyst with lower OSC. A statistical relationship has been developed to correlate HC performance with changes in OSC. The current algorithms are susceptible to false illumination of the Malfunction Indication Light (MIL) due to: 1. The accuracy with which the diagnostic algorithm can predict a catalyst malfunction condition, and 2. The precision with which the algorithm can consistently predict a malfunction. A new algorithm has been developed that provides a significant improvement in correlation between the EGO sensor signals and hydrocarbon emissions.

A common practice to improve vehicle fuel economy is to employ a fuel cut-off strategy on deceleration. This practice exposes the TWC exhaust catalyst to varying concentrations of oxygen depending on the vehicle control strategy. Since it is well known that exposure to oxygen at high temperature is deleterious to long term catalyst durability, it is important to understand the impact of oxygen concentration and temperature on catalyst performance. Simulated fuel cut agings at about 1%, 3%, and 9% oxygen concentration were compared to a full fuel cut aging (21% oxygen concentration). It was found that even small concentrations of oxygen at high temperature damaged catalyst performance. Deactivation increased with increasing oxygen concentration and increasing temperature.

Precious metal catalysts have been proven to be the most durable for reduction of automotive exhaust emissions. Currently, three-way catalysts are composed of mainly platinum and rhodium for reduction of CO, NOx and HC. Future catalysts are projected to contain increasing amounts of Pd to reduce current pricing of automotive catalysts. Mnolithic three-way catalysts containing Pt/Rh and Pd/Rh were aged on an engine dynamometer and were subsequently evaluated using engine sweep tests at various perturbation conditions of A/F ratio, amplitude and frequency. Stoichiometric light-off tests were also performed at various perturbation conditions. In addition, these catalysts were evaluated on FTP slave vehicles having widely different control strategies resulting in a substantial range of perturbation conditions.

Traditional approaches to pollution control have been to develop benign, non-polluting processes or to abate emissions at the tailpipe or stack before release to the atmosphere. A new technology called PremAir® Catalyst Systems1 takes a different approach and directly reduces ambient, ground level ozone. For mobile applications, the new system involves coating a heat exchange device in a vehicle, such as the radiator or air conditioning condenser. The catalyst converts ozone to oxygen as ozone-containing ambient air passes over the coated surface of the radiator. The technology is relatively simple and provides a positive benefit to the environment while being totally passive to the end user application. Volvo Car Corporation was the first automobile manufacturer to voluntarily introduce the technology on their S80 luxury sedan. Nissan Motor Corporation is also using the technology on their new Sentra CA (Clean Air) certified PZEV vehicle for California.

Classical approaches to pollution control have been to develop benign, non-polluting processes or to abate emissions at the tailpipe or stack before release to the atmosphere. A new technology called PremAir® Catalyst Systems1 takes a different approach and reduces ambient, ground level ozone directly. This technology takes advantage of the huge volumes of air which are processed daily by both mobile and stationary heat exchange devices. For mobile applications, the new system involves placing a catalytic coating on a vehicle's radiator or air conditioning condenser. For stationary applications, the catalytic coating typically is applied to an insert, which is attached to the air conditioning condenser. In either case, the catalyst converts ozone to oxygen as ozone containing ambient air passes over the coated radiator or condenser surfaces.

Recently Volvo Car Corporation introduced the new PremAir® catalyst system from Engelhard Corporation on their S80 luxury sedan and the new V70 estate wagon. In this paper, performance results of this catalyst system after long-term mileage accumulation will be presented. Urban taxi vehicles were used to test the catalyst over 110,000 miles. The rate of deactivation in long-term catalyst performance was found to be dependent on the radiator design, and was least for the radiator design with the highest total geometric surface area. Subsequently, a new catalyst version was developed in order to minimize the deactivation rate. This new catalyst has been evaluated under similar taxi driving conditions over 80,000 miles, and has shown improved durability performance.