High-Flow Cat vs Test Pipe: Which One to Opt?

Written by

Charles Bolte


Vernon Hoppe 

High-Flow Cat Vs Test Pipe

Installing the optimal exhaust system in your vehicle is a crucial factor on which your automobile’s whole performance and duration depend.

Choosing between high flow cat vs test pipe must be difficult for you as both exhaust systems are helpful according to their specific conditions and flow of gases.

Both systems come up with distinct features and specifications; high flow cat is more considerable for the environment, while test pipe has more prominence in the exhaust flow of gases.

Let’s read a comprehensive detail on their negative and positive implications.


Here is the short descriptive table, which makes it easy to know the difference between test pipe and catalytic converter.

Specifications High-Flow Cat Test Pipe
Performance Efficient exhaust flow by reducing backpressure.

Generate more power with a lower strain level.

Increase the exhaust flow and Boost the power performance.

Replace the OEM converter.

Legalities Legal in most states like the U.S.

Need timely cautions and inspections.

Illegal in most states, even in the U.S., California, and America.
Horsepower Ranges between 4hp to 10hp. Ranges between 4hp to 7hp.
Torque Can increase from 5ft lbs to 4000 rpm. Much higher than a cat pipe.
Long-lasting Duration Approximately >= 10 years

Depends on multiple factors like maintenance and driving conditions.

Depends on factors like scheduled maintenance, material quality, and driving regularities.
Cost More expensive

Around $300-$380

Comparatively less expensive

Around $195- $355


If you still need clarification on test pipe vs cat, here are some features that make them more distinctive.

1. Performance


Performance-wise, there will be a slight difference between horsepower and torque. Test pipes have a significant role in maintaining maximum performance by replacing OEM converters.

Although there will also be a considerable increase in horsepower, it makes it to lose torque.

However, the high-flow catalytic converter is crucial in removing the hindering factors increasing the exhaust flow and power output. There will also be a significant increase in horsepower; the ideal scenario is if your car is turbocharged.

2. Gas Emissions


In the case of a High-flow cat, you’ll see a reduction in the emission of gases, while in a test pipe, there would be an increase in the gas emissions with more sound. That was one reason it is illegal in many states like California and America.

3. Sound


You’ll find test pipes louder on the sound level aspect, while the cat pipe sound depends on the high-flowing system; the more flow, the more intense the sound.

In the cat-pipe, there would be an increase in high flow 100 0r 200 metallic cats from 2-4 Db. The increase in the sound level after installation will be around 17%.

Test pipes sound level usually refers to someone putting the alarms on louder noise, and there would also be a 70% increase in sound when it would cross from 3/4km rmp.

4. Exhaust flow


On the aspect of Exhaust flow, there is a slight difference in both; in test pipes, there would be increasingly high exhaust flow compared to Cat, with an empowered boost level.

However, you’ll see some restrictions or hindrances in the total cats in the exhaust flow speed, which helps make them legal.

5. Environmental Factors


Considering the environmental contribution of both pipes, Cat is more equipped to transform the toxic chemicals or gases into less-harmful gases before emitting them into the atmosphere than test pipes.

In test pipes, you’ll somehow see an increase in harmful gas emissions, which are toxic to the environment.

6. Legalities


It is a significant issue with both exhaust systems, but it is somehow relaxable for high-flow cats as it is legal in many states like the United States.

On the other hand, there is a highly asked question: Are test pipes legal? It is entirely illegal in most states like the U.S., California, and America. This will create a problem as it needs to pass the emission test.


Both high flow cat vs test pipe have their uniqueness and negative factors. But, before choosing the suitable pipe, you must consider these points:

  • Noise: Make the choice regarding the sound level of your preference.
  • Durability: Consider which system could be more durable for your vehicle and then choose.
  • Legal factors: You must know about legal issues for high-flow cat and test pipe.

Pros and Cons

Let’s give a read to those factors which would be beneficial and problematic for you.

High-flow cat

  • In high-flow cat systems, there is less backpressure factor, which helps to optimize the whole performance of the automobile.
  • The high-flow cat will decrease gas emissions and purify the harmful gases to comparatively less toxic.
  • High-flow cats are perfect for heavy-duty engines and help maintain better fuel economy.
  • Generating some bad smell
  • Check light engine might be on

Test-pipe cat

  • Test pipes are highly active for providing higher power output and significant
  • Generate loud engine noise
  • There is a hard sulfur smell issue in test pipes, which you would still sense inside the car and would be unbearable.
  • Test pipes have a critical role in contributing to environmental pollution. You would see a lot of toxic and harmful gas emissions.
  • In test pipes, there could be a possibility of getting the exhaust sides dark or black.

Which Type of Exhaust System is Better


Although both exhaust systems are highly effective, it depends on your requirements and preferences. Many people recommend Test pipes as they are more efficient in performance than high-flow cats, but there would be loud noise and legal issues.

It is better to go with high-flow cats, which are environment friendly too, with reduced chemical emissions, increased horsepower, and boosted performance. You will get some sound, but that would be bearable for you.


It is better to check the local management rules and regulations before deciding between a high flow cat vs test pipe. Although you must choose the exhaust system according to your requirements, you can select a test pipe if you could face smell or sound issues for a long time.

Considering all the essential components of both systems would be highly impactful in making the right decision for your car’s optimal performance.

5/5 - (1 vote)

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