LAS VEGAS, Nov. 2, 1999 - Thanks to a history of investment in catalytic converter research and technology, today's Walker® catalytic converters from Tenneco Automotive provide maximum emission reduction combined with increased vehicle power. But the road to optimum converter performance includes critical evolution in design and materials, too.

Catalytic converters were developed to reduce the amount of pollution generated by internal combustion engines. Early modifications to converter designs produced a cleaner running vehicle, but resulted in decreased vehicle power. Since that time the focus at Tenneco Automotive has been to merge lower pollution levels with high engine performance.

How They Work
Within the stainless steel shell of Walker aftermarket catalytic converters are ceramic substrates that are coated with a combination of platinum, palladium and rhodium. Hot gases containing pollutants travel through the exhaust pipe and eventually come in contact with the precious metals that are loaded on the substrate. When contact is made a chemical reaction takes place that weakens the molecular bond of the polluting chemicals and allows them to easily convert into the more desirable byproducts of combustion: H20 (water), CO2 (carbon dioxide) and N2 (nitrogen).

Three Types of Converters
There are three types of converters currently available in the North American market: oxidation converters, three-way converters (no/air) and three-way-plus oxidation converters.

Oxidation (two-way) converters represent the early generation of converters that were designed to oxidize hydrocarbons (HC) and carbon monoxide (CO). Although these units represent the most basic form of catalytic converter technology, they remain a viable pollution reduction option in some areas. Oxidation converters usually contain platinum or palladium.

In the early `80s, most vehicle manufacturers began using converters designed to reduce nitrogen oxides (NOx), in addition to oxidizing HC and CO. These three-way converters, which were used in conjunction with computer controlled engine systems and oxygen sensors, were employed to more precisely control the air to fuel ratio. These converters are referred to as three-way converters because they deal with three compounds: HC, CO and NOx.

Three-way converters that have a reduction and an oxidation catalyst together in one housing are called three-way-plus-oxidation converters. These converters feature air injection between the two substrates that aids the oxidation chemical reaction.

Today's catalytic converters represent the high level of technology and advanced materials ever developed. The result is reduced pollution emission levels combined with high engine performance.

Until the separation of its businesses, Tenneco is a $6 billion manufacturing company headquartered in Greenwich, Conn., with 40,000 employees worldwide. Tenneco Automotive is one of the world's largest producers and marketers of ride control and emission control products and systems, which re sold under the Monroe® and Walker® global brand names. Among its products are Monroe® Sensa-Trac® shocks and struts, Rancho® shock absorbers, Walker® Quiet-Flow™ mufflers and DynoMax™ performance exhaust products, and Monroe® Clevite™ vibration control components. Tenneco Packaging is among the world's leading and most diversified packaging companies.