Catalytic Converters: What they do, why they are there, and what you need to know about replacing them.
A catalytic converter is a component of nearly every exhaust system mounted to an internal combustion engine. They are most commonly found on construction equipment, generators, and automobiles. For the purpose of this article, I will mainly focus on the catalytic converters found in automobiles.
The manufacturer of every car maker must include them in the vehicles they produce to satisfy legal requirements set forth by the local government. They are legally required by authorities for public health and environmental reasons. The main purpose of catalytic converters is to reduce the amount of hydrocarbons and carbon monoxide produced by the combustion of fossil fuels. In layman’s terms, this reduces the amount of smog and greenhouse gasses released into the atmosphere. Catalytic converters are made up of a variety of metals, but most commonly include palladium, rhodium, and platinum. Catalytic converters are most efficient when they are hot, roughly 750° Celsius (about 1400° Fahrenheit). However, they will fail over time due to the amount of heat they routinely deal with or if they are operated at temperatures higher than 750° Celsius. The use of an oxygen sensor is integrated into the catalytic convertor to help the ECU (Engine Control Unit) regulate the exhaust gas temperatures (EGT) and ensure maximum life of the catalyst. When catalytic converter fail, the owner of the vehicle is required by law to find a suitable replacement that meets the local emission standards of the state or country.
Catalytic converters can be defined in two categories: two-way and three-way. The two-way catalytic converter oxidizes both carbon monoxide and hydrocarbons. The three-way does the same duties of the two-way, but also aids in the reduction of nitrogen oxides. In the United States, all catalytic converters that were used in new vehicle production after 1981 were required by law to be three-way converters.
Any aftermarket catalytic converter, or cat, that is sold as a factory replacement can be classified in two ways: standard or high flow. Standard catalytic converters are very similar to what the car manufacturer uses and is compliant with most states emission standards. Hi-flow catalytic converters are specially engineered to help a vehicle produce more horsepower and torque while still reducing harmful emissions. They help the engine create more power by reducing the amount of backpressure in the exhaust system. This means the engine doesn’t have to work as hard because it does not have to push hot exhaust gases through a restrictive pipe, rather the exhaust gases flow more freely exiting the vehicle. Hi-flow cats are most commonly used by car enthusiasts who want the most power from their car while staying compliant with local laws. It is important to read the documentation included with replacement catalytic converters to ensure they are compliant with your county, state, or national laws. There are a number of manufacturers who make replacement catalytic converters. Some of the most popular choices include Magnaflow, Pace Setter, and DynoMax.
Resources:
For more information, I’d definitely recommend researching Exhaust Systems and Catalytic Convertors, particularly MagnaFlow Catalytic Converters.