Updated at: 23-07-2022 - By: Lucas

A catalytic converter is a part of a vehicle’s exhaust system that reduces the amount of harmful pollutants released into the atmosphere. It accomplishes this by igniting a chemical reaction that transforms gases into less hazardous forms.

You’ll find two distinct types of converters on this page.

high-volume stock A high flow converter, on the other hand, can be upgraded using aftermarket materials, but a stock converter cannot.

What is a stock catalytic converter?

High Flow Catalytic Converter Vs Stock (2)

Helps to reduce water and carbon dioxide emissions from gasoline and diesel engines by using the stock catalytic converter. The honeycomb substrate is coated with platinum, rhodium, and palladium, the precious metals.

Toxic gases can be converted into less dangerous compounds by using this coating.

There are two types of stock catalytic converters: OEM (original equipment manufacturer) and aftermarket (aftermarket). Both the OEM and non-OEM converters can be used in conjunction with the stock converter (to regulate emissions).

Installing an aftermarket catalytic converter, on the other hand, can force the computer system of a car to enter a different mode, which may result in dash lights and engine difficulties.

In the United States, federal law mandates the installation of catalytic converters in all vehicles manufactured after 1996 in order to minimize pollution from internal combustion engines.

The California Air Resources Board (CARB) requires specific certifications, such as a six-digit identification number and the stamping of the manufacturer’s name, before an automobile without a catalytic converter can be fitted with one.

What is a high flow catalytic converter?

High Flow Catalytic Converter Vs Stock (3)

A higher volume of air can enter the engine through the exhaust system when using a high flow converter. As a result, since less energy is required to expel waste gases from the combustion chamber, a smaller engine may generate greater power.

Low displacement engines can benefit from high-performance exhaust systems in this fashion.

Cars that have been modified for burnouts or racing have high flow converters as well.

Using a high-flow converter, the builder knows that they want to remove as much exhaust gas from the engine as feasible. Utilize high-flowing converters for a louder engine, or use them for other purposes, such as enhancing fuel economy.

Differences between the stock catalytic converter and a high flow converter

1. Size and position

When compared to a high flow converter, the standard catalytic converter is huge and circular in shape. At the point at which exhaust gas reaches the engine compartment, the standard converter also sits low in an exhaust system. The exhaust manifold is then attached to the riser.

Even though the high-flow converter is not connected to the exhaust manifold, it puts more strain on other parts, particularly the valves. As a result, they are sometimes referred to as “hot side converters.”

2. Material

Alloy substrates in stock catalytic converters are made of palladium and rhodium. Palladium has nickel traces, as does rhodium, which is a heavier form of platinum.


As a catalyst for conversion, the substrate serves as the chemical agent that transforms toxic gases into those that aren’t so bad. Only one sort of material is used in high flow converters. The material is stainless.

3. Manufacturing process

Stock catalytic converters are constructed using a multi-step procedure that comprises many welding, shaping, and heat treating stations.

Stainless steel stamping can be used to manufacture high flow converters, resulting in a more cost-effective production process.

4. Physical appearance

On the outside, stock catalytic converters have a honeycomb pattern. Toxic pollutants can be filtered out of the vehicle’s interior. The stainless steel architecture of high flow converters makes it possible for gases to travel through swiftly and efficiently.

5. Pre-installation

It is possible to put a stock converter on any car prior to its construction using a stock converter kit. In order for the converter to fit into the surrounding systems, however, it is necessary to make changes to those systems. There are two options for installing a high-flow converter: at the dealership or by an experienced mechanic.

6. Cost

Stock catalytic converters are substantially more expensive to make than high flow converters because of the production procedure and the cost of the materials. In general, stock converters are two to three times as expensive as high flow converters because of this extra overhead.

7. Aftermarket usage

Catalytic converters are tough to modify, even for experts, because of their intricate design. The stainless steel or aluminized ceramic substrates that are available for aftermarket use in high flow converters can be easily modified by mechanics and amateur automobile enthusiasts alike.

8. Lifetime

It is recommended that catalytic converters be replaced after roughly 100,000 miles of use. It is possible to utilize high flow catalytic converters for up to twice as long, however they may need to be replaced depending on how often the automobile is driven and the materials used.

9. Effectiveness

However, not every mechanic believes that high-flow converters are a better option than stock catalytic converters. According to one theory, a high-flow converter puts a lot of stress on other engine components, which could lead to future engine problems or mechanical issues.

Similarities of stock catalytic converters and high flow converters

This type of catalytic converter is best suited for cars that are driven often and for short distances. An efficient high-flow converter may not be adequate for a sports car, which demands both excellent fuel efficiency and fast speeds in order to function at its best.

  • The goal is to make the most power possible while remaining street legal with a warranty
  • Both are tested in the same location under the same conditions
  • Both are tested on an engine dyno by trained employees of reputable companies
  • Both are advertised in similar ways
  • Consumer reviews of both are usually positive, even at optimal conditions.

Similarities between stock and high-flow catalytic converters

Stock catalytic converters and high flow converters have five things in common.

Increasing horsepower without increasing noise or reducing emissions is the most important commonality between high flow converters and stock catalytic converters.

Aftermarket catalytic converters, as long as they fulfill emissions standards, are popular because of the improved responsiveness and throttle response they provide.

How much horsepower does a high flow catalytic converter add?

An increase in horsepower of 10 to 20 percent is not uncommon with a high flow catalytic converter. When evaluating the additional horsepower provided by a high flow catalytic converter, it is critical to consider the quality of the manufacturing process.

A variety of engines can benefit from this upgrade, but forced induction engines are the most usual recipients. They’re not meant to be catalytic converters that last a vehicle’s lifetime. Replacement of these converters is required frequently in racing or engine tuning applications.

Do high-flow cats make exhausts louder?

If your exhaust system has high flow cats but you’re still hearing a raspy noise, it’s possible that the catalytic converter under your car is the culprit. This is not always the case. If the high-flow cats do their job too well, the harmful gases may not be able to escape.

Are all aftermarket catalytic converters high flow?

No. High-flow converters, mainstream converters, and stock converters are the three most common types of catalytic converters. Also known as performance converters are the first two components.

Catalytic converters from the three groups differ in their capacity for enhancing exhaust flow. An increase in flow of up to 70 percent can be achieved by using high flow converters. About 25 percent of the time, mainstream converters increase exhaust flow, while stock converters don’t normally enhance the exhaust flow at all.

Do high-flow cats require a tune?

It’s becoming increasingly common for high-performance automobiles to have high-flow cat converters, but do they require additional engine management system tuning?

No, that’s not always the case. Because the design and construction of high flow cats varies so widely, you should learn as much as possible about your unique model before deciding whether or not it requires tuning.

As long as they’re composed of stainless steel, aftermarket high flow cats can generally be treated as OE parts. Catalytic converter overheating is a common concern when using high-flow cats composed of ceramics or other high-temperature resistant materials.

Will high-flow cats pass emissions?

In recent decades, automobile manufacturers have made a concerted effort to build vehicles that are more fuel efficient and generate fewer pollutants from the exhaust.

As a result, numerous automakers equipped their vehicles with secondary air injection systems (SAI) to help decrease smog while travelling at moderate speeds.

These catalytic converters were often found to be undersized, resulting in failure during federal inspection.

Do high-flow cats cause the check engine light to come on?

There are concerns that high flow catalytic converters will create general or specific diagnostic trouble codes (DTCs) when installed since they replace stock catalytic converters.

High flow cats will not set off the check engine light, at least according to standard engine diagnostics.

Bottom line

A high-flow catalytic converter is an excellent choice for drivers who want to boost their car’s performance. Airflow and fuel economy are two of the many advantages it has over the stock catalytic converter. A high flow catalytic converter is a great option to consider if you want to boost your vehicle’s performance.