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Catalytic Converter Glossary From A – Z

Overwhelmed with jargon? This glossary gives you a comprehensive list of terms associated with Catalytic Converters. 

Body and Pipe Heat Shields:  Deflects heat created by the converter away from the vehicle’s undercarriage.

Catalyst:  A lead-sensitive substance, such as platinum, palladium, or rhodium, that accelerates or enhances a chemical reaction without being changed itself. When used in a catalytic converter, it can reduce the level of harmful pollutants in the exhaust.

Catalyst Cushioning Mat: The mat cushions the converter substrate, holding the ceramic catalyst in proper alignment. Creates a seal between the substrate and body, making sure all exhaust goes through the catalyst. Allows for thermal expansion of the body.

Catalytic Converter:  An automotive exhaust-system component.  Made of stainless steel, containing a catalyst to reduce oxides of nitrogen, and/or hydrocarbon, and carbon monoxide, in tailpipe emissions.

Catalytic Converter with Integrated Exhaust Manifold:  This type of catalytic converter has the Exhaust Manifold attached directly to it, in the engine bay.  Instead of underneath the vehicle in the traditional location. These are emissions certified the same way the original parts on your vehicle are.  These will bolt into place without any modifications what so ever. It’s highly recommended to use a new Exhaust Manifold Gasket when replacing a Catalytic Converter with Integrated Exhaust Manifold. 

 Dual Catalytic Converter:  Rather than having one cat converter to handle the task of converting the toxic emissions produced by the vehicle into less toxic ones, the vehicle will have two.   One in front of the other (identified as front and rear). This can be found in V6 Engine configurations.  This is not to be confused with Left and Right Catalytic Converters, found on other V6 or V8 Engine configurations, where the Catalytic Converters are parallel to each other under the body of the vehicle.

Exhaust Clamp:  Exhaust clamps are used with OE Catalytic Converter and exhaust pieces. These clamps are often referred to as V-band clamps, lap band clamps, narrow band clamps, U-clamps, or hanger clamps.

Exhaust Flange Gasket:  An exhaust flange gasket is a round-shaped gasket normally used to stop exhaust from leaking from the exhaust pipe and exhaust manifold of a vehicle. It is also called a donut gasket.

Exhaust Gaskets:  Exhaust gaskets are usually made from asbestos, soft metal, or a combination of both. You can find them between the exhaust manifold and cylinder head, the manifold U-pipes and collector pipe, and the collector pipe and exhaust pipe.

Exhaust Hangers:  The exhaust system hangers, also known as exhaust supports, are the mounts that are used to secure and support the exhaust pipes and Catalytic Converters to the underside of the vehicle. The exhaust hangers are usually made of rubber to absorb vibrations from the engine and to allow for flex for the exhaust to move as the vehicle travels.

Exhaust Insulators: Exhaust Insulators dampen vibrations from your exhaust while also insulating the heat from your vehicle. They are usually a small rubber piece that, over time, can tear, crack, or pop off. Your car’s exhaust system, along with channeling exhaust gases, also silences your engine’s noise

Exhaust Manifold: Engine exhaust manifolds are the metal components that are responsible for collecting exhaust gases and transporting them to the exhaust for expulsion from the tailpipe. They are bolted to the engine cylinder head(s) and are sealed using a gasket known as the exhaust manifold gasket.

Exhaust Manifold Gasket:  The exhaust manifold is a component of the exhaust system of a vehicle that connects to the cylinder head of the engine and collects gases and combines them from individual exhaust ports through to the rest of the exhaust system. This gasket is an incredibly important part of this system as it ensures the safety of the vehicle’s passengers by preventing toxic exhaust fumes from leaking back into the car or truck and causing harm to those who are riding in it. It is highly recommended to replace this gasket when installing a new Catalytic Converter with Integrated Exhaust Manifold.  

Monolithic Free-Flowing Substrate: The substrates are the backbone of the converter. This is where the proprietary mix of precious metal(s) and the washcoat formulated to store O2 allow the conversion process to take place.

O2(oxygen) Sensors: Another vital part of an emissions control system. These sensors are placed before and after the catalytic converter on an OBDII vehicle. They are designed to monitor the O2 storage efficiency of the converter. This information also allows the PCM to adjust fuel controls.

Stainless Steel Body:  For long life and durability. The ribbed body minimizes expansion and distortion, as well as forming channels that protect the cushioning mat from direct exposure to exhaust gases.

Three Way Converter: Three-way converters have been used in vehicle emissions control systems in North America – and many other countries – since 1981.  Three-way converters are used in conjunction with OBDII diagnostic systems on today’s vehicles. This system alerts the driver when the converter is not working at peak efficiency. A three-way converter (also known as oxidation/reduction converters) are designed to control levels of carbon monoxide, hydrocarbons, and oxides of nitrogen. Some three-way converters are equipped with an air injection tube, and this additional air, which comes from the air pump, assists the chemical reaction in the oxidation catalyst. Our converters all utilize three-way catalyst technologies and will operate in a two-way mode (controlling hydrocarbons and carbon monoxide) on older vehicles requiring a two-way converter.

 Three Way Plus Air Catalytic Converters: Three-way plus air converters were used in vehicle emissions systems in North America during the late ’70s and early ’80s.  Inside this converter there are two substrates. The front, coated with the precious metal rhodium, is used to reduce NOx emissions into simple N2 and O2. This process is most effective when little O2 is present (rich mixture). That is why it is located upstream of the air tube.  Since a rich mixture is high in HC and CO, an air pump and tube supply additional O2 to this mixture before it enters the second substrate.   The second substrate, coated with the precious metal’s palladium and platinum, allows oxidation of HC and CO to less harmful emissions CO2 and H2O.   This system was not very efficient and was phased out in the early ’80s, when the current three-way converter was introduced.

Two Way Converter: In this design, exhaust gases are directed to flow through the substrate containing precious metals platinum and palladium, which allow the chemical reaction to occur. The exhaust gases increase in temperature as the conversion process takes place.  Because of the intense heat created by this process, exhaust gases leaving the converter should be hotter than the gases entering the converter. This also explains why heat shields are required on most units.  Two-way converters operate relatively efficiently with a lean fuel mixture.