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When your engine burns fuel, it produces gases that are bad for the
environment. These noxious gases are hydrocarbons, carbon monoxide
and nitrogen oxides. To prevent the engine from polluting the
environment with these gases, we include a catalytic converter in our
emission systems.
The catalytic converter is installed in the exhaust line, between the
exhaust manifold and the muffler, and makes use of chemicals that act
as a catalyst. A catalyst is a chemical that causes a reaction
between other chemicals without being affected itself. In the case of
the catalytic converter, the chemicals it contains cause a reaction
in the pollutants in the exhaust. The pollutants are changed from
harmful gases to harmless ones before they are let into the
environment through the tail pipe.
Basically, the harmful gases enter the catalytic converter, a kind of
stainless steel container. The converter is lined with chemicals such
as aluminum oxide, platinum and palladium. These chemicals cause the
carbon monoxide and hydrocarbons to change into water vapor and
carbon dioxide. Some converters have a third lining of chemicals,
platinum and rhodium, that reduce nitrogen oxides (three-way, dual
bed converter).
The reason that leaded gas cannot be used in an engine with a
catalytic converter is that the lead coats the chemicals in the
converter. This makes them unable to do the job anymore, since the
chemical lining can't come in contact with the pollutants. At first,
this was a big disappointment, because lead acted as a lubricant and
helped to reduce wear on some of the engine parts. Luckily for our
engines and the environment (not to mention us), car manufacturers
soon got around the problem by making tougher parts and coating them
with special metal.
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