Are you a car enthusiast thinking of modifying your car? One of the first places you might consider is the exhaust system. But if you’re in California, you must know what’s acceptable. So, are high-flow cats legal in California?

High-flow cats are upgraded versions of regular catalytic converters filtering the exhaust fumes. They ensure free airflow, adequate processing of the exhaust, and prevent incorrect fuel mix. But they’re usually not permissible in California because they’re not CARB-compliant aftermarket products.

But if you’re planning to install high-flow cats, you need to make sure that you upgrade the whole exhaust system for the best result. Here, we discuss whether high-flow cats are legal in California.

What is a Catalytic Converter?

The catalytic converter is what converts the exhaust fumes into something safe when released into the environment. The combustion process necessary for getting cars moving involves chemical and mechanical processes. During the combustion, the piston and exhaust structure produces some chemicals.

The catalytic converter has a honeycomb structure with different coatings. Stock cats use ceramic honeycomb systems with precious metals within them. All these metals play a significant role in reducing emissions and purifying fumes. The metals are rhodium, platinum, and palladium.

These allow it to alter the chemicals as the exhaust fumes go through the structure and react as it passes from one stage to another. By the time the fumes come out, they’re clean and devoid of the chemicals that could cause smog or affect the environment. So, the converter is very important to the exhaust system.

The cat has a connection with the computerized engine system. Oxygen sensors monitor the fuel mix to ensure the fumes are harmless. Car engines usually produce three main emissions: carbon dioxide, nitrogen gas, and water vapor. The catalytic converter deals with the small and more harmful emissions such as hydrocarbons, monoxide, and nitrogen oxides.

What are High-flow Cats

High-flow catalytic converters are catalytic converters with fewer restrictions than the regular ones, allowing for an increased flow of exhaust gases. A high-flow cat doesn’t modify the flow of exhaust gases; it optimizes the car’s performance.

Although the high flow catalytic converter has a similar honeycomb design to the regular one, the design is more intricate. It has a wider cross-section which allows the gases to pass through, and there are more metals. This ensures quick catalyzation of the exhaust fumes. Doing this will increase the performance of the car. Cars with high-flow cats are usually louder, especially at wide-open throttle. But the noise isn’t necessarily significant.

Benefits of High flow cats

There are several benefits to adding a high-flow cat to your exhaust system. They include:

1.      Prevent Incorrect Fuel Mix

With high-flow cats, you can avoid improper fuel mixes that could damage the converter. This is especially possible in the newer fuel systems. The cat usually gets clogged over time, especially if the fuel system parts aren’t working properly. High-flow cats will most likely last longer than the stock replacement.

2.      Free Airflow

One of the many benefits of high-flow cats is that they won’t restrict airflow. This means that any restriction that could limit your vehicle performance is eliminated. The gas flow is efficient, and you can see the result in better performance.

3.      Adequate Processing for The Exhaust System

If you drive a large vehicle, high-flow cats are generally ideal. For a vehicle with a big engine, the high-flow cat provides adequate processing for the fumes that it produces.

Can You Use High Flow Cats in California?

High-flow cats are illegal in California. This is because they don’t have a California Air Resources Board CARB number. You’ll need a CARB sticker or direct OEM replacement parts if you plan to replace any part of your car in California.

The high-flow cat will most likely fail visual inspection. The catalytic converter is an emission control device. It will reduce the toxic pollutants from the internal combustion engine by converting them into harmless compounds.

If you’re using an aftermarket replacement converter, it has to be CARB compliant for California Emissions Certified cars from the 2001 model to the latest. In vehicles that are 2000 and older, which meet the Federal/EPA-only emissions standards, it’s also permissible. However, unlike stock cats, high-flow cats don’t filter as many chemicals. This means the O2 sensors will detect it and cause the check engine light to come on. Without the correct cat, it’s impossible to pass the smog test.

Sections 27156 & 38391 of the California Vehicle Code prohibit selling, advertising, or installing any device that will alter the performance and design of any vehicle pollution control system or device. Some exemptions for aftermarket equipment won’t reduce the effectiveness of the pollution control system or device. So, if it’s possible for the high-flow cats not to exceed the vehicle emissions standards, they might be permissible.

Should You Add High Flow Cats to Your Car

If you’re planning to add a high-flow cat to your vehicle, it shouldn’t be in a vacuum. It works best when completely modifying your car exhaust system and then adding it as the crown piece. A regular exhaust system might be restrictive for a high-flow cat. In most cases, the best way to use a high-flow cat is on supercharged or turbocharged cars. For it to work best, the car must have at least 20% more horsepower than the stock capacity.

Normally, a high-flow cat would be great for your car. But since you’re in California, you may not be able to get this. However, it’s possible to find high-flow cats that will meet the strict standards in places like California, where emission rules are stricter. 

In Conclusion 

If you want to improve your vehicle performance, modify your exhaust system or replace the old converter, you should consider a high-flow cat. But you need to ensure that the high-flow cat will pass the tests and inspections in California. The chances of this are slim, but it could be a risk worth taking.