The Different Types of Catalytic Converters

What is a Catalytic Converter?

Following the Clean Air Act of 1970, automakers were tasked with reducing tailpipe emissions from the vehicles they produce. A critical component in satisfying emissions regulations has been the catalytic converter, sometimes called a “converter” or simply “cat” for short. Catalytic converters use chemical processes to convert harmful pollutants into less harmful emissions.

Early catalytic converters were a two-way design, whereby exhaust gases flowed through a substrate that exposed them to heavy metals (such as platinum and palladium) as a means of causing chemical reactions. Two-way catalytic converters do a poor job of reducing NOx (nitrogen oxides), which led to the development of three-way plus air converters. In addition to the two oxidation catalysts, they add a third chemical process: a reduction catalyst that converts NOx into N2 (nitrogen) and O2 (oxygen). Most vehicles built since the early 1980s use three-way catalytic converters that store and release oxygen as needed. 

What is a Direct-Fit Catalytic Converter?

Direct-fit catalytic converters have fittings on each end of the device that allow them to be fitted or bolted directly into the vehicle. Little to no exhaust fabrication (cutting, welding or articulation) is required and they can usually be installed with basic hand tools. Because they are designed to exact specifications for each year/make/model of vehicle, direct-fit converters tend to be more expensive than universal converters.



    • Little to no exhaust fabrication required
    • Easy to install
    • Bolt-on design
    • Vehicle Specific

    What is a Universal Catalytic Converter?

    As the name implies, universal catalytic converters can be installed in almost any vehicle, as long as the diameters of the inlet and outlet tubes are the same on the converter and the exhaust system, and it is the correct converter for the particular vehicle and the state it will be registered in. (For more information on how to buy a catalytic converter, click here.)



      • Universal fitment
      • Requires professional installation
      • Affordable

      What is a Manifold Catalytic Converter?

      Similar to direct-fit converters that bolt directly into a vehicle’s exhaust line, manifold catalytic converters are integrated into a vehicle’s exhaust manifold, a component that collects exhaust gases from multiple cylinders into a single pipe. Because of their specialized design and fitment for specific vehicle models, manifold converters are typically more expensive than direct-fit or universal converters. In terms of installation, this type of converter requires the entire exhaust manifold to be removed and replaced.



        • Specialized design & fitment
        • Requires professional installation, or advanced mechanical knowledge

        What is a CARB Compliant Catalytic Converter?

        The California Air Resources Board (CARB) has its own set of environmental regulations that CARB compliant catalytic converters must meet for vehicles registered and operated in California- these limitations do not apply to vehicles registered and operated outside of California. Introduced in 2009, the CARB Compliant law states all aftermarket catalytic converters sold in California must meet low emission vehicle (LEV) standards. CARB is mostly known for providing innovative approaches for complying with air pollution rules & regulations. Even though CARB regulations are currently implemented in California, many other states are following the same structure.


        What are Federal/ EPA compliant Catalytic Converters?

        If the vehicle is registered and operated outside of California, there are two Federal EPA compliant catalytic converter choices:


        1. Heavy Metal Catalytic Converters: HM converters are suitable for non-California (49-state) vehicles and are certified by the Environmental Protection Agency (EPA), but not CARB.
        2. OEM-grade Catalytic Converters: OEM-grade converters meet both EPA and CARB standards. However, if a vehicle is registered in California, only CARB-approved converters can be used.

          If you aren’t sure which one you need, refer to the emissions tag in your vehicle’s engine compartment, which should be located under the hood, on the radiator core support, or on one of the strut towers.

          Need to buy a new catalytic converter? Give us a call at 1-800-990-0905 and we’d be happy to help.