Tuesday, March 18, 2014
Why Does My Car Have Three Catalytic Converters
Catalytic converters use exhaust heat trapped in a matrix of ceramic plate and precious metals to change exhaust gases chemical composition to a more benign form. Quick-moving gases might sometimes lack the opportunity to catalyze fully, which may require two or more converters.
Converter Function
Converters contain a honeycomb-like ceramic matrix with thousands of tiny passages. Exhaust flows through these passages, combining with the platinum, rhodium, palladium and cesium on the passage walls to add or subtract nitrogen or oxygen atoms. This gain or loss converts the toxic molecules in the exhaust into more benign forms.
Emissions Requirements
Different countries and unions have different emissions requirements and require different catalytic converters. The European Union disallows the use of nickel in converters but permits copper (which the United States does not). Most large car manufacturers offer several variations on the same chassis to market all over the world. Using more than one converter allows the manufacturer to meet local emissions standards while using the same basic chassis worldwide.
Modularity
Not all car manufacturers produce their own catalytic converters; many converters are outsourced from specialty catalytic converter manufacturers. Because most cars come with a number of different engine options, manufacturers may need to mix and match different converters to meet emissions requirements for a particular engine-chassis combination.
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