How Do Catalytic Converters Work and How to Break In a New One


The golden years of unrestricted automotive development are long gone. Today, car manufacturers worldwide are continually struggling to meet the industry’s expectations, all while sticking to the ever-growing emissions regulations. A catalytic converter is a device that was specifically designed to help with this struggle. Today we’ll talk about what exactly is a catalytic converter and how one works. We’ll also go over the breaking-in procedure for a new cat.

Catalytic Converter 101: Anatomy and Function

Internal combustion engines have evolved a lot since they were first invented. The vehicles we drive today are light years ahead of ones we drive just 30 years ago, let alone something like a Model T. That being said, modern engines are still not clean. No matter how hard we try, it’s tough to eliminate the harmful emissions that are the byproduct of combustion.

It wasn’t until the 1980s that the world even started looking into the harmful effects of automotive emissions. Several studies were launched to find that emission gases from your average car were terrible for one’s health.

The EPA was founded to track emissions and enforce restrictions. So far, the EPA has achieved a significant reduction in emissions thanks to its work.

Since there was no real way of making the engines of the era more efficient and thus cleaner, another solution had to be invented. That solution came in the form of a catalytic converter.

Catalytic Converter 101: Anatomy and Function

What is a Catalytic Converter

Catalytic convert is an integral part of automotive exhaust systems on modern cars. It’s a filter of sorts that cleans up the exhaust gases, removing the extremely harmful particles. In essence, the converter itself is quite simple.

The way its set up involves two stages. Each stage of the catalytic converter features a honeycomb-like structure made of a platinum alloy. The first stage is usually a platinum-rhodium combo, while the second stage features a platinum palladium honeycomb.

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How does a Catalytic Converter Work?

As we’ve mentioned before, even the most modern internal combustion engine leaves behind some residue due to combustion. The efficiency is never 100% when it comes to converting fuel into energy. Residual gases pushed out from the cylinder during the engine’s exhaust stroke are packed with harmful particles.

You’re mainly looking at CO2, NOx, CxHx, and many other harmful gases that aren’t safe for humans or the environment. By pushing these gasses through the catalytic converter’s honeycomb structure, you’re essentially weakening the bonds between atoms of nitrogen and oxygen.

Nitrogen will form a stronger connection with the material the catalyst is made of, thus breaking up the harmful gas into nitrogen and oxygen. Both of these are perfectly harmless for the environment and humans.

Keep in mind that this is a simplified explanation. The actual catalytic process is a bit more complicated. You should know that catalytic converters are around 80-90% effective, although that rate of efficiency is continually being increased.

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The Issues with Catalytic Converters

Catalytic converters or cats are great for the environment, but not so much for the vehicle’s performance. The issue with most cats is the fact that they choke up the exhaust, preventing the engine from achieving its max potential.

That’s why many drivers chose to de-cat their vehicles, despite this being extremely illegal just about everywhere around the world. Performance isn’t the only reason why cats are being removed left and right these days. They can fail too.

The Issues with Catalytic Converters

How to Diagnose a Bad Catalytic Converter?

Cats go bad on vehicles all the time. Just like oil filters or any other type of automotive filters, catalytic converters can clog up. This often happens on older vehicles or high mileage vehicles that have seen their fair share of the road. Symptoms of a bad catalytic converter are fairly straightforward.

  • Tangible Drop in Performance – One of the first symptoms of a bad cat is a drop in performance. Your vehicle might feel sluggish like it’s under much more load than it actually is. You’ll also notice a tangible reduction of acceleration.
  • Smoke Coming Out of the Exhaust – Once a catalytic converter stops performing its function, you might notice dark-colored smoked coming out of your exhaust. The smell of the fumes will change too. Smelling sulfur is one of the common symptoms of a bad cat.

Once your catalytic converter fails, you have two options – get a new one or simply remove the old one. By removing your cat, you’ll get rid of the issue for free, but you’ll also no longer be street legal in many jurisdictions. Additionally, your vehicle will dump all of those harmful gases straight into the environment.

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How to Break In a New Catalytic Converter

To start the break-in procedure, start the car after you’ve replaced the cat. Let the car idle in place without applying any gas. When the engine warms up to its operating temperature, get inside and give the car enough gas to bump the RPMs to around 2500. Hold it there for 2 minutes and then release the gas. Shut the car off and let it cool down completely. And that’s your entire catalytic converter break-in procedure.

The reason why cats need to be broken in before use, comes down to gradually exposing the new components to high heats and pressures. This initial warm-up phase allows all the materials inside the catalytic converter to set in place. Performing a new cat’s gradual warm-up is also necessary to burn off the binding that keeps the matting compressed.

If you were to subject the new cat to an average drive, or even worse, a more dynamic drive, you’d most likely end up with dislodged components within the cat housing. Considering how expensive cats are, that would be one pretty costly mistake.

You’d be surprised how many brand new catalytic converters are ruined because people are never told how to break them in properly. You’ll save yourself a lot of trouble by following this extremely simple and fast break-in procedure.

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Where to Find Replacement Catalytic Converters?

If you’re looking for replacement catalytic converters for your European car, you’re in the right place! eEuroparts.com is one of the leading suppliers of quality genuine, OEM, and aftermarket car parts for various European car brands. We also carry genuine replacement catalytic converters for a variety of brands.

To find a replacement cat for your car, simply head over to our online store and input your car’s information into our search tool. Once done crunching the data, our system will show you a list of parts that match the input.

Alternatively, you can also use our VIN tool by typing in your car’s VIN. You’ll get much more accurate results this way. In case you have any questions regarding our catalog or any specific products, please reach out to our customer support center. We’re standing by to offer whatever information you need and help you select the right parts for your car!

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