I recently became intrigued by the idea of using a high-flow cat in my car. Hearing about the performance boost made me even more eager to install an HF catalytic converter.
However, I came across something during the research that made me pause and rethink my decision.
High flow cats do not meet emission standards, thus failing emissions tests. A 200 CPI HF cat is likely to pass tailpipe emissions, but not a visual test. As a result, it is illegal in the US since it violates emission regulations.
In the article, I have outlined the primary reasons why a high flow catalytic converter fails emissions testing. I will also cover all of the laws regarding HF cats in detail. Let’s get started right away!
Why High Flow Cats Won’t Pass Emmsions?
The motor produces poisonous gasses, such as hydrocarbons, carbon monoxide, and nitrogen oxides. Being a part of the engine’s pollution control system, high flow cats regulate and refine the harmful gas produced inside the motor.
How do high flow cats achieve this? To do this high flow cats attract those smog and harmful gasses towards their chemical analyst. Chemical analyst is made up of platinum or palladium which neutralize if not minimize the harmful effect of the gasses and allow them passing.
But there’s a problem: those hellbent harmful chemicals don’t like to undergo refining treatment. In order to guide the smog and gasses, catalytic converters are built on a honeycomb structure.
The question is why high flow cats don’t pass emissions tests?
The straightforward answer is it doesn’t comply with the testing standard. Roughly the amount of smog, pollutants and gasses.
Read Also: Can I Pass CA Smog With Catalyst Monitor Not Ready?
Are High Flow Cats Legal?
In accordance with EPA regulations, replacing a catalytic converter with a performance one such as a high flow cat is not legal.
In addition, authorities can accuse you of breaking the law simply for replacing the cat. There is a legal obligation that prevents you from changing your catalytic converter unless it has been declared defective by a technician.
Even when the cat is proven to have failed, the law mandates that you replace it with another OEM catalytic converter.
This is precisely where motorheads are able to exploit a loophole. You see, OEM and high-flow cats do not differ much when it comes to being detected by authorities. As a result, many high-flow cats slip through inspections unnoticed.
Will A High Flow Catalytic Converter Improve Emissions?
Yes, high-flow cats can improve emissions. Since high flow cats don’t impede gas flow like traditional cats. Unlike the structure of traditionally structured cats, high flow cats structure is very convenient for restriction-free gas emissions.
Here’s how the structure of high-flow cats is different from conventional cats.
High flow catalytic is made up of honeycomb structure which is more wide and expanded than the traditional one. Since converters control the flow of the emissions, the performance of a cat is largely determined by the flow rate. And, the flow rate can be raised in two ways.
- By increasing the overall cross-section of the honeycomb.
- Widening the passage to facilitate flowing exhaust gasses.
Implementation of the first concept comes with a challenge and that is it takes additional space. So, a big question comes into play:
What should be optimized space or performance?
But, there are some brands out there that did outstanding jobs here without sacrificing performance and space.
So, figuring out the best high-flow cats is mandatory.
>> Speaking of the question, whether high-flow cats increase the emission or not?
Yes, undoubtedly high flow cats increase the emission flow. And throughout this section, I explained how.
Will High flow Cats Improve Performance?
In the preceding section, I showed how high-flow cats improve emissions flow. But does that mean an improved performance?
Well, here’s the catch. It’s not necessarily that an installation of high-flow cats will improve performance although it significantly improves emission flow.
That said, high flow cats don’t significantly boost performance. However, if you get other spare parts of the engines upgraded, you will likely see a notable boost in performance.
Summary: If your engine is stock and your catalytic converters are relatively new, you won’t experience much performance gain by using high-flow cats. A stock catalytic converter (especially one on a newer stock vehicle) isn’t that restrictive unless significant performance upgrades have been made.
Heads Up: Is Upgrading To High Flow Cats Worth It?
No matter how good features a product offers that won’t help if those features don’t benefit you.
Just like that, it doesn’t matter how awesome high-flow cats are unless they can improve your car’s performance as a whole. In essence, if the investment in upgrading cats to high-flow cats is not worth it, you shouldn’t attempt for.
However, I’m here to answer you if high-flow cats are worth it or not. To assess that we need to think if high-flow cats improve engine performance with respect to the price point.
That being said, high-flow cats can be a wise investment if you upgraded other parts of your car or if your car is of new model. It’s better to replace the catalytic converter if your car is more than 8 years old. And, in such a case you should invest in the latest cats, right? But before that, you need to consider the pros and cons.
In essence, upgrading to high-flow cats is worth it as long as your car is new or upgraded other parts of the car are as well.
Here are the 3 Best High-Flow Cats in the Market
| Image | Product | Rating | Price |
|---|---|---|---|
 |
AUTOSAVER88 ATCC0007 Universal High-Flow Catalytic Converter | 4.4 out of 5.00 | Check Price |
 |
Flowmaster 223 Series Universal Catalytic Converter | 4.3 out of 5.00 | Check Price |
 |
MagnaFlow Universal Catalytic Converter | 4.2 out of 5.00 | Check Price |
1. AUTOSAVER88 ATCC0007 Universal High-Flow Catalytic Converter
Key Features
- Universal Fit: Since it has a universal fit, you can install the cat in any vehicle.
- Durable: The product is built with a heavy-duty T409 steel shell that guarantees a long lifespan.
- Better Reaction Area: The converter is equipped with honeycomb ceramic substrates on the inside. They facilitate the increase of reaction area and ensure the coating surface has enough catalysts.
2. MagnaFlow Universal Catalytic Converter
Key Features
- Corrosion-resistant: One of the most common problems with catalytic converters is corrosion. Thankfully, this cat’s stainless steel construction will prevent this issue.
- EPA-compliant: The cat is designed to comply with the EPA’s requirements. Hence, penalties are less likely to result from its use.
- No Check Engine Light: When the check engine light comes on, it is always a cause for concern. Although you know everything is fine, the check engine warning is still distressing. With this converter, you won’t get such warnings.
3. Flowmaster 2000130 Catalytic Converter
Key Features
- Lightweight: The Flowmaster cat has a compact and lightweight design. It is the ideal solution for those looking for enhanced performance at the lowest weight possible.
- Easy Installation: Many people, especially beginners, find installing a cat quite challenging. Thanks to Flowmaster’s quick and easy installation process, even beginners will have no problem installing it.
- Warranty: You can rely on this product to last a long time. Nonetheless, if any issue arises, you can simply contact the manufacturer as it comes with a massive 5-year warranty.
FAQs
Do High Flow Cats Increase Sound?
A cat with a high flow will definitely be louder. Depending on what you are searching for, you may find a few loud noises, if any.
Read More: Does A Bigger Exhaust Tip Make It Louder?
Will a High-Flow Cat Cause a Check Engine Light?
Yes, the check engine light appears if there is a high flow catalytic converter. It is because the computers presume that HF catalytic converters perform way less efficiently than they should.
There is an effective way to solve the issue by tuning the air/fuel numbers. Remember that the computer receives data directly from the O2. Hence, adjust the air/fuel numbers to your O2 reading to clear the check engine light.
Will a High Flow Cat Throw a Code?
Each OBD2 compliant car has two oxygen sensors, one before and one after the catalytic converter. Typically, the ECM will cause the P0420 code if the secondary oxygen sensor does not read the same as when stock catalytic converters are used.
Will A High Flow Cat Pass Mot?
Despite passing the emissions element of the MOT test, Milltek Hi-Flow cats are not suitable for road use because they are not tested under the 2009 ruling.
Are High Flow Cats Legal In CA?
No, high-flow cats aren’t legal in CA. A catalytic converter will be legal in CA if it comes with a CARB sticker and it’s not common to see cats with such stickers.
Final Thoughts
Catalytic converters are an indispensable and vital element of a car’s engine. And, high flow cats are just the latest addition to catalytic converters.
There are tremendous benefits high-flow cats offer. But, there is a pitfall regarding the emissions test. High-flow cats can’t pass emissions tests.
Although, high-flow cats can pass one part of the test but can’t pass the manual test. That said, it can’t pass the emissions test.
Throughout the post, I not only broke down the nitty-gritty of why high-flow cats don’t pass emission but also discussed the bells and whistles of it.
If you still have any questions about the topic, comment below.
