How Many Catalytic Converters In A Car? – Checking Guide

Car exhaust is a major contributor to the environment. The car exhaust converter is like a silent “bodyguard” to help make the environment greener – cleaner.

But how many catalytic converters in a car? How do I know if it’s still good or not?

Don’t worry; we’re here to help you with these questions. Scroll down and get the answer.

What Is A Catalytic Converter?

How Many Catalytic Converters In A Car?

A catalytic converter (cat), a redox converter, is an effective vehicle emission control device. People often apply it to internal combustion engines that use gasoline or diesel fuel.

This is a metal box with a honeycomb filter made of Ceramic stone or metal. Covering this filter element is a catalyst layer that can create a chemical reaction with harmful emissions.

This catalyst compound is usually rare metals such as platinum, gold, rhodium, etc.

Thus, this equipment is responsible for converting harmful gases (CO, NOx, HC) and environmental pollutants in the exhaust fumes into less harmful ones (CO2, H2O, N2).

Although it has a very simple structure and can only convert about 90% of harmful compounds, it still brings tremendous effects.

Since 1975, catalytic converters have rapidly gained popularity as laws on emission restriction and environmental protection become stronger.

How Many Catalytic Converters In A Car?

The catalytic converter and the exhaust manifold are the components that play a major role in converting the exhaust gas before it is released into the environment.

Inside the exhaust manifold, the rear exhaust will swing through the commutator to the converter.

Before, most cars had a converter unit; however, the number can be larger depending on the number of vehicles’ exhausts.

In recent years, the Environmental Protection Agency (EPA) has increasingly tightened regulations on the Clean Air Act, especially in the United States.

This forces car manufacturers to come up with many innovations to improve the performance of this system.

As a result, most modern fuel-powered cars try to have at least two sets of cats, except for electric vehicles, which do not.

How To Know How Many Catalytic Does A Car Have?

As noted above, on each exhaust pipe is an adapter. The number of exhaust pipes is the most accurate basis for knowing how many cadillac converters your 4-wheeler has.

So the simplest way to determine its count is to check this pipe. You need to move down to the car’s rear, crouch, and count how many smoke holes there are.

If you only see one exhaust, it only has one cat; when your car uses a dual exhaust system, it will have two.

Types Of Catalytic Converters

Types Of Catalytic Converters

At the beginning of the article, we also discussed the question “how many catalytic converters does my car have?” and how to determine its quantity.

So how many types of cats are in use on the market? They are divided into three categories as follows:


To be honest, two-way converters are the basic solution automakers use to deal with emissions and environmental laws, such as the US Clean Air Act.

This is the most basic design, where exhaust gasses flow in one side and out the other. The name comes from the two chemical reactions that take place inside:

  • Oxidize hydrocarbon (HC) to CO2 and H2O
  • Oxidize CO to CO2

In the two major car markets, the US and Canada, this was the most common type in diesel and gasoline engines.

Until 1981, the two-way cat had to give way to the newer three-dimensional version because it did not respond effectively to NOx.


Compared to the two-way version used in the first stage, this three-way unit offers more improvements, making transferring toxic gases from the engine more efficient.

The three-way converter is divided into two steps. The first deals with NOx emissions, which are easier to do without oxygen.

This is followed by using an air pump to add oxygen to the mix. It is even essential for the chemical reaction used to reduce carbon monoxide and hydrocarbons to CO2 and H2O.

Diesel Engines

The most common cat in diesel engines is DOC (Diesel Oxidation Catalyst). While gas engines use sparks to ignite the fuel, diesel engines use oxygen and compression.

Every diesel cat has a diesel oxidation catalyst, which functions similarly to an air pump on a gas engine.

In addition to the gasses emitted by ICE, diesel engines also emit other particles, which makes the battle over diesel intense.

Thus, a diesel particulate filter (DPF) is needed to capture the bad stuff, storing it until it is burned. This process’s result is water and CO2.

The efficiency of these devices is usually only 90%, but it also helps to significantly remove the smell of diesel oil and visible soot particles.

Pros And Cons Of Catalytic Converters?

Any piece of machinery, no matter how many benefits it brings, has many advantages and disadvantages. These cats are no exception:


  • Simple structure
  • Converts harmful gasses to safer wastes
  • The performance is quite great
  • Diverse types, suitable for many types of engines
  • Consume less fuel
  • Has fairly high durability, about 50,000 – 100,000 miles
  • Easy to clean with warm water and degreaser


  • There is no consensus on the required regulations in all countries.
  • Only 90% of the toxic gas can be converted, and some still leak into the atmosphere, causing harm to human health.
  • Dismantling may cause a loss of torque when operating the vehicle.
  • Making noise while driving
  • Takes part in engine performance

Can A Car Run Without A Catalytic Converter?

Yes! Cars can still operate normally even without this conversion. It is not a device that will affect the movement of the motor.

However, everyone really should have it in their car. A good cat helps limit the release of harmful emissions.

The more people use it, the more harmful gases we can filter and contribute to reducing the burden on the environment. This is a good habit for drivers.

In addition to the self-consciousness that comes from the above benefits, catalytic converters are also required for cars in some countries, such as the United States.

Driving without cats will expose you to penalties as required by law.

Symptoms Of A Faulty Catalytic Converter

The cats can carry cargo for a long time, but it can become congested over time. Car owners should bring their vehicles to a repair shop for assistance when experiencing the following signs:

  • Reduced operating performance: Poorly operated equipment will cause exhaust gas to be trapped in front of the converter, creating back pressure. This pressure can affect the car engine’s operation; the car shows signs of slowing down when moving on the road.
  • Running out of fuel fast: When the active converter decreases efficiency, it consumes more fuel to drive the reactions. As a result, you will find your car has to fill up faster.
  • Engine stops running: The device, when overheated, will cause the motor to stop working. If a fuel-rich mixture enters, it ignites and melts the catalyst components under high heat.
  • Check engine light on: The check engine light is the easiest sign to tell if a cat is having problems. Take your car to the professionals quickly if you notice it suddenly lights up.


What Vehicles Have More Than One Catalytic Converter?

As mentioned above, cars equipped with only one converter are often old, so the performance is quite poor.

As the issue of environmental protection becomes more urgent, manufacturers also focus more on this detail by increasing its quantity.

You can easily find modern vehicles using two to four sets at the same time. Some models include Cadillac, Volvo, Lincoln Town, Dodge Grand Caravan, etc.

Are The Front And Rear Converters The Same?

No. There is a certain difference between them regarding the gas they will combine to produce oxidation and reduction reactions. Specifically:

  • The front one takes care of CO (Carbon Monoxide) and HC (Hydrocarbon) treatment.
  • The rear one takes care of NOx (Nitrogen Oxide) safety.

Both functions are equal; neither is more important than the other. They work independently for the common goal of cleaning emissions.

How Many Catalytic Converters Are In A BMW Car?

BMW is one of those brands interested in creating fuel-efficient and safe products.

Thanks to their advanced vehicle emission treatment technology, their cars always appear in the list of environmentally friendly products.

Here, the number of BMW converters depends on many factors, such as vehicle model, year of manufacture, engine size, etc.

Most BMW versions on sale have two cats per exhaust. In particular, the one on the back is larger than the one on the front.

For example, the BMW E90 và E92 has two sets located at the front of the car and in the middle of the exhaust; The E60 has what sits on top of the turbocharger’s exhausts, etc.

However, some newer and more advanced versions have up to 4 or 8 sets.

BMW pays great attention to the performance of these components so that they can best meet emission standards in many countries and still help owners save fuel.

Besides, these devices have a long lifespan, so their catalytic converter price is higher than many other brands. The more precious metal it contains, the higher its price, ranging from 800 – 2500 dollars.


Above is the answer to the question: how many catalytic converters in a car? And related information. To help reduce air pollution, ensure your car has these cats and is still in good working order.

Hope this article is useful to you. If you have any other questions, please leave us a comment below.

Thanks for reading.

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