Why Do You Need a Catalytic Converter?


Practically every car sold in the United States since the mid 1970s has been equipped with a catalytic converter. These exhaust system components reduce the amount of harmful gases that are released into the atmosphere as byproducts of an internal combustion engine. Some say that a car's performance will improve after the cat (as they are sometimes called) is removed, but the basis for this claim is not backed up by any authority. Here's why you need a catalytic converter on your car.

The facts

  • Catalytic converters are required equipment for all gas and diesel powered cars on the road today. You can't buy a car that does not have one. Removing the catalytic converter from your car is in violation of the federally mandated Clean Air Act, and may also be in violation of state law as well. If you remove the cat, you will fail the emissions test when your car is next inspected. If you drive a car that has on board diagnostics, removing the converter will cause your "Check Engine" light to come on.


  • The catalytic converter removes hydrocarbons (unburned fuel), carbon monoxide (CO) and oxides of nitrogen (NOX) from the exhaust before it reaches the muffler. There are two main types of catalytic converters: Two-way and three-way. Two way converters, which were the first to be put into general use, remove only the hydrocarbons and CO.

How they work

  • Catalytic converters essentially just burn the remaining hydrocarbons, CO and NOX to create harmless CO2, water and nitrogen. As temperatures approach 1,400° Fahrenheit the catalyst found inside the converter (usually platinum, rhodium and/or palladium) helps the oxidization of the exhaust gases without undergoing any chemical change to itself.


  • The Clean Air Act of 1970 was passed to prevent the dangerous emissions of fossil fuel combustion from becoming a serious threat to the quality of life in this country. Hydrocarbon emissions can contribute to many illnesses, including the irritation of the throat, lung and the eyes. Oxides of nitrogen are a component of smog and they produce ozone, which is a smelly irritant of the eyes and respiratory system. Carbon monoxide is extremely toxic and can cause death if inhaled in large concentrations.


  • After a catalytic muffler that was developed in the late fifties suffered failures due to lead additives in the gasoline, the first catalytic converters were created in 1975 by John Mooney and Carl Keith. These were two-way converters, and it wasn't until 1981 that the three-way catalytic converter was introduced.

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  • Photo Credit "Hong Kong Boing!" is Copyrighted by Flickr user: LiveFromAmsterdam (hans van rijnberk) under the Creative Commons Attribution license.
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