What Are Test Pipes? Everything You Need to Know

Ask any mechanic, "How can I gain more power in my car?" And the first thing he/she will tell you to do is upgrade the exhaust system. Why the exhaust pipe, you may ask? It's because getting more power out of your engine starts and ends with airflow.

Little tweaks to the exhaust system, like cold air intake replacements, catback exhausts, and headers, may not appear to be a big deal of an upgrade. However, these minor changes might make a huge difference in power and performance.

Among these various upgrades, the replacement of a catalytic converter with a test pipe is the most common upgrade done by car enthusiasts. In most cases, the catalytic converter represents the biggest restriction in the exhaust system because it controls the emission but also tightens the flow of the exhaust gasses.

So, what is a test pipe?

Test pipes are called by many names, straight pipes or high-flow pipes. These pipes are pieces of the aftermarket exhaust system, bypassing the catalytic converter and the muffler. It is a long, round piece of metal, normally made from stainless steel or metal aluminum.

In essence, testing pipes are widely applied in sports cars, muscle cars, modified vehicles, and all kinds of fast-running motors.  It is not recommended for daily driving vehicles.

Benefits of Test Pipes

Here are a few notable benefits you get after replacing your catalytic converter with a test pipe.

More Horsepower and Torque

Smooth flow of gas reduces backpressure, improving the performance of an engine. This results in noticeable gains in both horsepower and torque, particularly for turbocharged engines.

Better exhaust flow

The free movement of exhaust gasses, through test pipes, helps to dispel old gases from the engine. Meaning, the used exhaust gases leave the cylinders fast and allow fresh air and fuel into the cylinders for better efficiency.

Lower Exhaust Temperatures

A test pipe can help lower the temperature of exhaust gases because it has fewer limits in the exhaust system. This helps the engine perform better and last longer, especially during high-performance or track uses.

More Aggressive Sounds

Test pipes remove the muted sound that catalytic converters produce in a system, enabling your vehicle to have a much louder and more robust exhaust sound. The tone will vary by the make and model of the car, modifications done to the engine, and the design of the test pipe.

Lose Weight

Catalytic converters are heavy components. If they are replaced with a lighter test pipe, it will lower the overall weight of the car, improving performance and handling a bit.

Less Expensive for Race Applications

A test pipe is a cheaper option than fixing or replacing a catalytic converter for cars that are only used on tracks. This helps racing fans who want the best performance without worrying about emission rules.

Drawbacks of Using Test Pipes

As the saying goes with everything there is an equal and opposite reaction. With its advantages, test pipes also come with a few disadvantages. Here are some of the drawbacks of using test pipe.

More Emissions

Test pipes eliminate catalytic converters, which raise emissions of highly harmful gases like carbon monoxide and nitrogen oxides. The outcome could be air pollution and environmental harm.

Legal Issues

Test pipes are banned in many locations due to bypassing emissions regulations. Fines, failed inspections, or even having your car impounded can result from using them.

Loud Noise

Without a catalytic converter, ‌exhaust noise can be much louder. This can be annoying and may break local noise laws, which can lead to more legal problems.

Warranty and Insurance Risks

Installing test pipes can invalidate your car's warranty or lead to insurance claims being denied. The manufacturers or insurance companies may also frown upon the change in the exhaust system.

Check Engine Light Activation

The catalytic converter removal usually turns on the check engine light because it fails to get the correct reading from the oxygen sensors. This may be challenging to diagnose other real engine problems.

Possible Damage to Other Components

Test pipes can change the flow of the exhaust. That could lead to overheating or harm to other components, like the exhaust manifold or sensors, which weren't meant for the changed setup.

Resale Value Effect

Cars with test pipes can deter potential buyers because of the legality of such a modification, the increased noise level, and the high expense of reinstalling the original catalytic converter. This can lower your car's resell value.

Types of Test Pipes

When trying to maximize the performance of your vehicle's exhaust system, the type of test pipe used can go a long way in performance and sound. Let's explore two of the main types: resonated and non-resonated.

Resonated Test Pipes

Resonated test pipes feature a sound-dampening chamber or baffle in their construction. The chamber works to dissipate extreme noise and disagreeable tones from a straight-through, non-resonated piping setup. The benefit of using this pipe is that it produces a more redefined and tolerable exhaust note, especially at higher RPMs.

Non-Resonated Test Pipes

Non-resonated test pipes are straight-through designs devoid of any sound-absorbing elements. This produces a more 'in-your-face' and usually louder exhaust note.

The lack of backpressure gives the best possible flow of exhaust gasses, hence wide performance gains, especially for those who do high-performance driving. But when it comes to sound it can be annoying for some fellows but can be quite exciting for some enthusiasts.

Are Test Pipes Legal?

There are set regulations in many regions, especially where the environmental impact is strictly governed, to limit emissions excessively. Most of such regulations target modifications that can further deteriorate air quality.

Legality Issues in Various Regions

United States

• Federal Regulations - Federal regulations in the U.S. mostly pertain to emissions standards. There are no direct federal statutory prohibitions against test pipes, but installation may make the vehicle non-compliant with emissions standards, particularly in states like California with strict regulations.

• State-Level Regulations - States like California have strict emissions standards, and the installation of test pipes will not pass these tests. Consequences include fines, problems with vehicle registration, and possible litigation.

• Local Regulations - Other local jurisdictions may enact further statutory restrictions on vehicle modifications. It is worth checking if any local ordinances or regulations apply to any modification being planned.

European Union

• Euro Standards - European Union authorities have put in place what are known as euro standards to control vehicle emissions. In as much as test pipes, per se are not banned, changing a vehicle's emission system may make it fall out of specifications.

• Nation-specific Legislations - EU member states may have different laws concerning vehicle modification. Consultation with the local authorities or qualified mechanics is recommended in understanding such specific regulations of your country.

Other Countries

• Asia - Countries like Japan and South Korea have strict emissions standards, and modifying a vehicle's emissions system can lead to legal issues.

• Australia - Australian regulations vary by state and territory. While some regions may be more lenient, it's crucial to check local regulations before installing test pipes.

Potential Penalties and Inspection Issues

• Fines - Fines can be from as little as a couple of dollars on minor offenses to very large ones depending on the severity of the offense.

• Impoundment of Vehicle - Under certain circumstances, vehicles with illegal settings can be impounded by the authorities.

• Vehicle Registration Issues -The installation of test pipes in your car may make it stand out as a problem during the time of its registration or re-registration.

• Failed Emission Tests - This may further lead to limitations in running your vehicle or may completely disallow its usage altogether.

Users' Tips

Knowing the legal scale and being able to take proper measures will allow you to enjoy the performance of your vehicle and avoid serious legal issues. To avoid possible legalities and fines, the following should be considered.

• Check Local Regulations - Always research and follow local, state, and federal regulations.

• Seek Professional Advice - Consult with a qualified mechanic or automotive expert to understand the legal implications of modifications.

• Consider Alternative Modifications - Explore other performance-enhancing modifications that are legal and comply with emissions standards.

• Observe the Check-Up Procedure - If your state requires periodic vehicle checkups, be ready to correct any emissions system problems with your automobile.

Do Test Pipes Add Horsepower?

Yes, test pipes add horsepower. A smoother exhaust flow would translate to the engine "breathing" better. That means it can intake and expel air with more ease. This results in higher volumetric efficiency.

Other factors contributing to horsepower are reduced backpressure. The engine doesn't have to fight as hard to push the gasses out when there is less backpressure.

While test pipes can certainly add some horsepower, several variables make the differences vary.

• Engine Modification - Highly modified engines with performance exhaust systems may realize small gains with the addition of test pipes, other engines may experience significant performance changes.

• Vehicle Type - The type of vehicle in which the test pipe is being installed can be another factor. Sportier cars with performance-oriented engines may realize more substantial gains over sedans or SUVs.

• Driving Style - Your driving style can also affect how much horsepower you think you've gained. Aggressive drivers who like to run their engines at higher RPMs will, as a rule, notice the reduction in exhaust restrictions much more than more conservative drivers will.

It's tough to give an exact number of horsepower gains due to the factors described above that vary between setups. However, you can expect an addition of 5-10 horsepower with a new test pipe.

Test Pipes vs. Downpipes: What’s the Difference?

Test pipes and downpipes remain two of the most discussed topics in the circle of enthusiasts. While they appear similar to uninformed readers, they differ quite significantly in both function and benefit.

Test Pipes

A test pipe is essentially a straight piece of piping that replaces the catalytic converter in the exhaust system. This allows for a better flow of exhaust, leading to potential gains in performance.

Yet, test pipes are not devoid of serious downsides. By bypassing the emissions control system, they can significantly increase tailpipe emissions and, depending on one's region, may lead to legal problems because of stringent emission standards.

Downpipes

A downpipe is the portion of the exhaust that routes gases from either the turbocharger or engine manifold to the catalytic converter or test pipe. Performance downpipes optimize the flow of the gases passing through the downpipe section and, as a result, can increase horsepower and torque output.

Aftermarket downpipes often feature a range of different sound profiles- from subtle to all-out aggressive. You can tune your exhaust note to your preferred flavor.

Should You Straight Pipe Your Car?

Unless you know exactly what you're doing and have big plans for your entire exhaust system, installing a test pipe is a great way to upgrade your exhaust system. If it is the sound of the exhaust you want, then the best thing would be to install a good quality catback exhaust system.

What's your take on testing pipes? Would you run them in your car? Let us know by leaving a comment below!

Test Pipes Recommendation