Does Every Car Have a Three-Way Catalytic Converter?

No, not every car has a three-way catalytic converter. These devices, which reduce harmful emissions (carbon monoxide, hydrocarbons, and nitrogen oxides), are primarily fitted to petrol-powered vehicles. Diesel cars typically use a different system, such as a diesel particulate filter (DPF) and selective catalytic reduction (SCR). Electric vehicles, like the Tesla Model 3 or Nissan Leaf, don’t have exhaust systems at all, so they lack catalytic converters entirely.

The three-way catalytic converter became standard in petrol cars after stricter emissions regulations were introduced, particularly in the 1980s and 1990s. Modern petrol models, including popular options like the Ford Focus or Vauxhall Corsa, will almost always have one. However, classic cars built before emissions laws were enforced may not.

For diesel vehicles, the focus is on reducing particulate matter and nitrogen oxides, which is why they rely on DPFs and SCR systems with AdBlue fluid. If you’re unsure whether your car has a three-way catalytic converter, check the owner’s manual or consult a mechanic.

Not every car has a three-way catalytic converter. The three-way catalytic converter can simultaneously convert the main harmful substances in exhaust gases into harmless substances. With increasingly stringent environmental requirements, more and more vehicles are equipped with exhaust catalytic converters and oxygen sensors. Through oxidation-reduction reactions, carbon dioxide and nitrogen are installed in the engine's exhaust pipe, hence it is also called a three-way catalytic converter.

Reasons for the failure of a three-way catalytic converter:

1. Excessive temperature:

At normal temperatures, the three-way catalytic converter does not have catalytic capability. Its catalyst must be heated to a certain temperature to gain oxidation or reduction capabilities. Typically, the ignition temperature of a catalytic converter is 250-350 degrees Celsius, and its normal operating temperature is 400-800 degrees Celsius.

When the catalytic converter is working, it generates a significant amount of its own heat. The higher the oxidation temperature, the higher the temperature. When the temperature exceeds 1000°C, the catalyst in its inner coating can sinter and die, and vehicle self-ignition accidents are more likely to occur. It is essential to control various factors that lead to an increase in exhaust gas temperature, such as delayed ignition timing, ignition sequence disorder, or misfires, which can allow unburned mixed gas to enter the catalytic converter, causing excessively high exhaust temperatures and reducing the converter's efficiency.

1. Chronic poisoning:

The catalyst is highly sensitive to elements such as sulfur, lead, phosphorus, and zinc. Sulfur and lead come from gasoline, while phosphorus and zinc come from lubricating oil. These four substances and their oxide particles formed during engine combustion can easily adsorb onto the catalyst's surface, preventing the catalyst from contacting the exhaust gases and thus losing its catalytic function, a phenomenon known as poisoning.

1. Carbon surface accumulation:

If a car operates at low temperatures for extended periods, the three-way catalytic converter cannot activate, and the carbon soot emitted by the engine will adhere to the catalyst's surface, preventing contact with CO and HC. Over time, the pores of the carrier can become clogged, affecting its conversion efficiency.

1. Deterioration of exhaust:

The catalytic converter has a limited capacity for converting pollutants, and it is necessary to minimize the original exhaust gases through in-engine purification technology. If the concentration and total volume of exhaust pollutants are too high, or if the mixed gas is too rich, the catalytic converter's ability to convert pollutants will be affected, reducing its conversion efficiency. Excessive amounts of HC and CO entering the catalytic converter can cause excessive oxidation reactions, generating large amounts of heat that can lead to overheating and damage to the converter.

From an environmental perspective, the three-way catalytic converter is crucial for petrol cars but irrelevant for diesels and EVs. Petrol engines rely on it to neutralise toxic gases, while diesels use alternative tech. Electric vehicles, producing zero tailpipe emissions, don’t need one. If reducing your carbon footprint matters, consider an EV like the BMW iX—no converter required.