Few parts on a car are surrounded with more mystery and misconception than the catalytic converter. How could it not be? It comes as a "sealed box" with no user serviceable parts, they tend to be expensive, and have a somewhat generic sounding name; so why do cats cost so much? How are they made? And what exactly goes on inside a catalytic converter? Hopefully we’ll be able to shed some light on this metal mystery and clear up some confusion with this explanation below.
The Ceramic Matrix
If we’re going to explain how catalytic converters work, first we’re going to have to talk a little about their basic construction. The most important part of a catalytic converter is the ceramic matrix. This honeycomb is made predominantly of a ceramic called cordierite, chosen for its heat resistance, thermal stability, and durability under extreme heat. The honeycomb is created via an extrusion process in which lengths of honeycomb are squeezed through a die and supported by computer-controlled jets of air that keep the honeycomb straight as it leaves the machine.
Washcoat and Precious Metal Catalysts
Once the honeycomb is fired and set, it receives a washcoat of various oxides combined with the precious metals that function as the actual catalyst. The washcoat is used because it most evenly disperses the metals throughout all the pores in the ceramic matrix and maximizing surface area is important for efficient catalytic function. The metals are generally mixed so as to best utilize their individual properties. Most catalytic converters in the United States use some combination of platinum, palladium, and rhodium. Outside of the United States, copper has been tried, but will form dioxin, a toxic substance with carcinogenic properties. For this reason, its use has largely been abandoned. In other places in the world, materials like nickel, cerium in washcoat and manganese in cordierite are used but again, each has its disadvantages.
How Catalytic Converters Reduce Emissions
Redox Reactions Explained
Earlier catalytic converters were of a two-way type, but due to stricter environmental regulations, a more elaborate 3-way converter has become the norm. Catalytic converters work using what is called a redox reaction, which means that once the catalyst is up to operating temperature (anywhere from 500 to 1200 degrees Fahrenheit), both an oxidation reaction and reduction reaction are occurring simultaneously. Although sounding complicated, what this means is that molecules are simultaneously losing and gaining electrons, or harmful gases are chemically transformed into less harmful ones before exiting the tailpipe. Redox reactions are extremely common and a fundamental process of many things in our environment, such as photosynthesis and rust formation.
The Role of the Converter Shell
The ceramic matrix is fragile and wouldn’t survive long hanging under a car if it was left to fend for itself, especially with constant exposure to heat, road debris, and vibration. This is where the metal shell comes in. Most catalytic converters feature more than one ceramic “brick” in a shell. The shell helps the catalytic converter manage heat and keep the ceramic bricks in their ideal operating temperature range. Proper thermal control is essential for emissions efficiency, longevity, and consistent performance.
Insulation and Vibration Control
Between the steel of the shell and the ceramic matrix is a heat-resistant insulating barrier that locks the bricks in place inside the shell and limits the amount of vibration that the ceramic experiences. MagnaFlow uses vermiculite-based mat for this due to its ability to expand and fill the gaps between the "brick" and the shell when heated, though other manufacturers may do things differently.
Testing and Validation
Once assembled, catalytic converter shells are welded shut and flow tested to verify consistent exhaust flow and structural integrity before shipping. These validation steps help ensure the converter functions as designed when installed on a vehicle. MagnaFlow uses 5 gas in-house emissions testing to be sure that every new part passes stringent quality and performance standards.
Why Catalytic Converters Matter
Catalytic converters may seem complex, but understanding their construction and how they function offers insight into how important they are for vehicle emissions, performance, and longevity of your vehicle. From the ceramic matrix and precious metal catalysts to the protective shell and rigorous testing, every part of the process plays a role in transforming harmful gases into safer emissions while maintaining reliability on the road. With proper design and manufacturing, these “sealed boxes” are not only effective at reducing pollutants but also durable enough to last the life of the vehicle.
Whether you’re maintaining a daily driver or upgrading your vehicle's performance, choosing a catalytic converter that meets or exceeds OEM standards is essential for emissions compliance, drivability, and longevity. Explore MagnaFlow’s full line of catalytic converters to find options engineered with premium materials, state-of-the-art manufacturing processes, and the industry-leading designs your vehicle needs.
