Best High Flow Catalytic Converters-2021 Reviews and Top Picks

Nowadays, people are looking for more environmentally-friendly options for getting around. If purchasing a rand-new hybrid or electric car is out of the question, the best thing you can do for both your car and the environment is to a high-flow catalytic converter.

High-flow catalytic converters can boost your vehicle’s performance without spiking the emissions output. After making contact with a chemical catalyst, exhaust fumes are converted into less harmful compounds like CO2 and water.

In this guide, we’ll show you what the 5 best high-flow catalytic converters are and how to choose the most appropriate model for your vehicle.

Top 5 Best High Flow Catalytic Converters


AUTOSAVER8 ATCC0006 is a universal, 400-cell catalytic converter made of stainless steel. This heavy-duty component keeps emissions at an all-time low while also maintain an optimal, steady flow rate. Inside of this high-flow cat is a coating of ceramic substrates, which keep internal reactions and structure running optimally.

The ATCC0006 features inlet and outlet diameters of 2.5 inches and measures in at 11 inches in length. The total weight of this high-flow cat is just under three pounds and doesn’t come with a hardware kit. The standard 2.5-inch inlet and outlet mean you don’t need to make very many modifications to set install this unit. However, if your car’s pipe is not the right size, and if you don’t have any experience in welding and cutting, you should consider hiring a professional mechanic to fit the unit onto your vehicle.

This high-flow catalytic converter is designed specifically for older vehicle models from 1996 and up. However, some users have installed this high-flow cat onto cars from the late-1980s with surprisingly satisfying results. While EPA and ODB II compliant, this high-flow cat is illegal to use in the state of California. If you reside in the golden state, this unit is sadly not for you.

Overall, this unit has left countless customers thoroughly satisfied. By replacing the stock converter of older vehicle models with the ATCC0006, you might be able to raise the horsepower of your baby girl with this catalytic converter.

AUTOSAVER88 ATCC0006 2.5' Inlet/Outlet Universal...
172 Reviews
AUTOSAVER88 ATCC0006 2.5″ Inlet/Outlet Universal…
  • AUTOSAVER88 brand new universal fit catalytic converter is…
  • Features heavy-duty stainless steel construction, internal…
  • Standard 2.5″ inside diameter inlet/outlet, 11″ overall…


  • Stainless steel construction
  • Internal ceramic substrate coating
  • EPA compliant
  • Made for cars from 1996 and up
  • Rarely triggers MIL indicator
  • Long-lasting


  • Not CARB compliant
  • May require professional installation


One of the best high-flow catalytic converters for older cars is the ATCC0007. Like the ATCC0006, this unit (made by the same company) is a universal, 400-cell cat that can drop the emissions levels of cars made in the late-1990s and even some earlier models, according to customer feedback reports.

The 400-cell means larger holes to promote better flow, thereby sacrificing very little in terms of performance for emissions requirements. Installing the unit is as simple as the ATCC0006—it features 2.5-inch inlet and outlet diameters that connect to most standard exhaust pipes. However, you may need to welt and/or cut your exhaust pipe to make it fit with this unit. Leave this to the pros if you’re inexperienced in welding and operating a bandsaw.

The specific design of the ATCC0007 is made to prevent the MIL indicator from needlessly triggering. Plus, this high-flow cat comes with an O2 port that further improves the heating process of unburned exhaust fumes, thereby further improving emissions test results in old makes and models.

The exterior of this high-flow cat is made of durable stainless steel for long-lasting performance. This unit also uses the same ceramic substrate will undoubtedly work more effectively at converting harmful gases than your old car’s OEM catalyst.

AUTOSAVER88 ATCC0007 2.5' Inlet/Outlet Universal...
375 Reviews
AUTOSAVER88 ATCC0007 2.5″ Inlet/Outlet Universal…
  • AUTOSAVER88 brand new universal fit catalytic converter is…
  • Features heavy-duty stainless steel construction, internal…
  • Standard 2.5″ inside diameter inlet/outlet, 11″ overall…


  • Great flow, minimal power loss
  • Heavy-duty, anticorrosive construction
  • EPA and OBD II compliant
  • Additional O2 port for good measure
  • Fits most standard exhaust pipes with minimal cutting
  • Backed by 5-year warranty


  • May require cutting and welding
  • Not CARB compliant

#3. Walker 93253

The Walker 93253 is yet another universal-fitting high-flow catalytic converter that is ODB II compliant. This unit will fit onto any vehicle made after 1996 and, as some customers claim, works wonders on cars made in the 1980s as well. This unit, like the previous ones, is not CARB compliant, so sadly, our Californian readers will have to look elsewhere.

This universal high-flow cat comes with a 2.5-inch inlet and outlet, so it’ll fit on the most standard exhaust pipes with minimal or no welding at all. Measure the diameter of your car’s exhaust pipe beforehand before settling on this particular model.

The exterior is made completely out of durable stainless steel, which, based on customer feedback, can last more than five years of heavy-duty driving. It features a similar ceramic substrate as the AUTOSAVER88 models, but the cell count figure remains unknown. That said, you don’t have to worry about this unit not passing emissions testing since it’s compliant with federal EPA regulations.

You will not find an O2 port in this unit, but with proper installation, you can reduce the amount of exhaust coming from your 30-year-old vehicle. Plus, this high-flow cat is specifically designed to prevent triggering your car’s MIL indicator.

Overall, the Walker 93253 is a great catalytic converter that works wonders and bringing older cars to life. At just 11.5 inches long, there shouldn’t be much trouble about fitting this unit onto your car’s exhaust pipe, though some welding might be necessary.

Walker Exhaust Ultra EPA 93253 Universal Catalytic...
182 Reviews
Walker Exhaust Ultra EPA 93253 Universal Catalytic…
  • EPA COMPLIANT — For use on OBDII vehicles, 1996 and newer….
  • DURABLE — Features stainless-steel body with aluminized…


  • Excellent performance
  • Usable on older vehicles from the 1980s (per customer claims)
  • Features ceramic substrate
  • Durable stainless-steel construction
  • Does not trigger check engine light
  • EPA and OBD II compliant


  • May require welding
  • Not CARB compliant

#4. Eastern Universal Catalytic Converter 70318

The 70318 by Eastern Industries is another universal catalytic converter that features 2.5-inch ports. In fact, you won’t find very many different specs from this unit compared to the best overall pick (ATCC0006), but it is slightly stubbier.

At 10 inches, you may experience more difficulty installing this high-flow catalytic converter onto the exhaust pipe of over cars (OBD II compliant, 1996 and up) due to the longer builds of OE converters. We wholeheartedly recommend that you speak with a professional before getting this installed—both to see whether this is a good fit for your vehicle and to get an estimate on installation costs.

Like the previous models, the Eastern 70318 is made of durable stainless steel. It’s also backed by a 5-year warranty or 50,000-mile travel distance. Make sure that this unit is compatible with your vehicle, otherwise you run the risk of voiding the warranty. Sadly, those in California are not allowed to purchase this unit either.

Eastern Industries has used NANO technology while creating this high-flow cat to ensure that the ceramic substrate is distributed more uniformly along the 10-inch body. This increases the conversion efficiency of harmful gases into water or CO2, thereby ensuring that your old car from the 1990s will pass emissions tests with flying colors.

Eastern 70318 Catalytic Converter (Non-CARB...
556 Reviews
Eastern 70318 Catalytic Converter (Non-CARB…
  • This item is not for sale in California/Non CARB compliant
  • Converter Body Material: Stainless Steel.



  • Trusted company
  • Generous 5-year or 50,000-mile warranty
  • ODB II and federal CPA compliant
  • Shorter body means smaller power loss
  • Affordable option
  • Fits on nearly any make and model


  • Can be tricky to install
  • Not CARB compliant


Last up on our list of the best high-flow catalytic converters is another AUTOSAVER88 product—this time, it’s the ATCC0026. This is a unique cat in the sense that it’s a direct fit unit instead of universally fitting. This means that you weld it to keep in in place on exhaust pipes larger or smaller than 2.5 inches (the size of its inlet and outlet ports).

The flanges on either side of the ATCC0026 keep it snug in place during installation. A direct-fit high-flow cat like this one doesn’t require very much welding, if any, so you’ll have to make certain that the unit is right for your vehicle. It’s also OBD II compliant, so it’ll work great on cars from 1996 and up. This model is designed for Honda CR-Vs from 1997 to 2001, but if your car’s exhaust pipe is identical, then you shouldn’t have any problems.

Like other products on this list, the ATCC0026 is made of stainless steel with an interior ceramic substrate. There’s no cell rating on this model, but based on customer reports and considering its federal EPA compliance, there shouldn’t be any issues with emissions testing results.

Without an O2 port, you need to ensure that your vehicle’s sensors are in tip-top shape. Faulty sensors can result in damage to your vehicle’s spark plugs and quite possibly negatively impact fuel economy.

AUTOSAVER88 Catalytic Converter Compatible with...
166 Reviews
AUTOSAVER88 Catalytic Converter Compatible with…
  • AUTOSAVER88 direct-fit high flow catalytic converter is…
  • Features heavy-duty stainless steel outer shell construction…
  • The standard OE specification flanges are designed for easy…



  • Direct fit, made specifically for certain vehicle types
  • Increases car performance
  • No MIL issues (if properly installed)
  • Simple DIY installation
  • EPA and OBD II compliant
  • 5-year, 50,000-mile warranty


  • Non-CARB compliant
  • Only suitable for certain car models

All You Need to Know About High Flow Catalytic Converter

Here’s a quick overview of what you need to know about high-flow cats.

How High-Flow Catalytic Converters Increase HP

This might not always be the case. Unless your car’s engine has been packed with performance-upgrading features, you might not get the HP increase you’re looking for. On average, you can see a 5 to 60-HP increase.

  • Only heavily modified vehicles will experience a high HP increase
  • Average HP increase range between 5 and 60 HP
  • Regardless, high-flow cats will improve emissions ratings

Stock vs. High-Flow Catalytic Converters

In older vehicles, the main reason to upgrade to an aftermarket high-flow catalytic converter is to make it drivable by following modern emission laws. If your aim is to increase performance, especially in a new vehicle, the stock catalyst may suit you just fine.

  • Necessary upgrade for older vehicles
  • Better emission ratings than most OEM catalysts
  • Aftermarket can be more efficient than stock
  • Can boost power without affecting fuel economy

Advantages of a High-Flow Catalytic Converter

The advantages of these units range from increase vehicle performance and better emissions ratings. However, as we explained in an earlier section, the increase in performance depends on whether you’ve added performance-adding features to your car’s engine.

  • Possible HP increase
  • Less emission means a cleaner planet
  • You can drive your old super-polluting vehicles again
  • Less noise output
  • Can use high-performance fuels to power your engine

Important Q/A About High Flow Catalytic Converter

1. Why do I need a high-flow catalytic converter?

The stock cat on your car isn’t as restrictive as you might seem until you’ve modified your vehicle. In this case, you will need to upgrade your OEM to an aftermarket high-flow cat. Also, if you plan on driving a car made in the 80s or 90s, you have to get a new high-flow catalytic converter.

2. How long do high-flow catalytic converters last?

Their warranties generally last for up to five years or for 50,000 miles. However, the models listed above can last for upwards of seven years without showing any signs of trouble. That said, make sure you check the high-flow cat regularly to see that it’s not leaking exhaust or that it isn’t damaged in any way.

3. Can I salvage a dirty high-flow catalytic converter?

Sadly, you cannot. You can extend the life of your catalytic converter with regular cleaning, but after the ceramic substrate has become damaged beyond repair, your only choice is to replace it with a new unit. The good news is that you can sell the stainless-steel material. Some have sold their old high-flow cats for $50!

4. What are the effects of a bad/faulty high-flow catalytic converter?

With a dirty or improperly installed high-flow cat, your car will experience a noticeable drop in fuel economy. This can also happen to a dirty catalytic converter, so always make sure to give it a quick look on occasion to ensure it’s still performing optimally.

Final Verdict

In today’s guide, we’ve shown you what our picks of the best high-flow catalytic converters are. We’ve included both universal and direct-fit models, all of which come with 2.5-inch inlet and outlet ports. Do some research on your vehicle to see whether the models listed above are right for your car. Feel free to speak with a professional mechanic regarding the compatibility and installation (universal-fit) of your new high-flow catalytic converter.

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