Downpipe Vs. Exhaust: Function, Power & Which is Louder?

The downpipe system is entirely different from the complete exhaust system and produces obvious results when installed in a car. A full exhaust system changes the exhaust, starting from the header to the tailpipe. In some rare cases, it does not include the catalytic converter. 

The downpipe system is a pipe that, as the name implies, links the exhaust system with the turbocharger. The turbocharger uses the exhaust system to power itself. In contrast, the turbocharger uses the downpipe to redirect exhaust gasses from the engine back into the exhaust system. 

downpipe connected to turbo

downpipe connected to turbo

Downpipe Vs. Exhaust (Comparison) 

Comparison  Downpipe  Exhaust 
Sound  Louder Loud
Price  $200-$300 $150-$2000
Emission  Yes  Yes 
Legal No Yes
Performance  40 HP  10%
Catalytic converter  Depends Depends
Check engine light  Higher Chances  Depends

Functions: Downpipe Vs. Exhaust,

A downpipe exhaust system is different from the exhaust system, and they function differently. They both have different placement and results. The downpipe functions as a means of distributing exhaust gasses throughout the engine and also works with a turbo. The exhaust comprises the full exhaust system starting from the exhaust connected to the engine down to the tailpipe or sometimes the muffler.



The downpipe has a major function of moving exhaust gasses throughout the engine system. It directs these gasses from the turbine system to the exhaust system. It is a very crucial tool, especially in turbocharged engines. 

It is essential to turbo-charged engines because the charger is powered by the exhaust system and can not function properly if the exhaust gasses do not flow properly within the engine system. The downpipe ensures that the turbocharger gets the exhaust gasses it needs to work.  

The downpipes that come with a catalytic converter helps the system clean the exhaust gasses. As much as the catalytic converter is useful to the downpipe system, it also has its downside. The catalytic converter in the downpipe can perform restrictive functions, which may cause your engine to lose power. 

The downpipes come in two types if you deal with aftermarket downpipes: Cat and catless. We will be focusing on the catted downpipes. What makes the catted downpipes special is the fact that it has a high-flow catalytic converter.  

The high-flow catalytic converter removes the restriction with a catalytic converter and allows for more exhaust flow in the engine. This will allow the engine to perform better and also add more horsepower. 

READ MORE: What’s Better Catted or Catless Downpipe?


However, the aftermarket exhaust includes pipes, catalytic converters, and mufflers. They also include any modification to these parts or the whole exhaust. An exhaust system helps the car direct exhaust gasses away from the engine or the car itself.

Some common types of aftermarket exhaust modification that could be done on your car, includes cat-back, which replaces the part of the exhaust system from the catalytic converter to the muffler, axle-back, which changes the rear axle to the muffler, and the header-back or full exhaust which will change the entire exhaust system. 

Each type of these modifications will give your vehicle a varying kind of gain.     


The downpipe is a great way to modify your exhaust system. It adds about 20 horsepower to your engine. Also, the aftermarket exhaust system gives additional horsepower to your vehicle’s engine. 


The catted downpipe exhaust system is a great way to add that extra horsepower that your car needs. Hence, the catted downpipe comes with a high-flow catalytic converter which removes the restriction placed by the normal converter and allows for a better flow of exhaust gasses in the exhaust system. 

As we know, the better the flow of gasses in the engine system, the better the engine’s performance. With a catted downpipe, your engine system is sure to add about 20 horsepower. 

However, when installing a downpipe to add extra horsepower, we recommend that you avoid getting a catless downpipe. A catless downpipe will add greater horsepower to your engine. This is because it does not come with a restrictive catalytic converter that could reduce the engine’s horsepower. 


The aftermarket exhaust system also adds horsepower to your engine. The aftermarket exhaust system can add up to 10% horsepower to your engine system. Although the horsepower addition solely depends on the type of aftermarket exhaust installed to your vehicle. 

The idea of improved power in the engine system is linked to how much airflow the exhaust system will allow you to have. The aftermarket exhaust system provides a better medium for exhaust gasses to escape from the combustion chamber. 

READ MORE: Does Aftermarket Exhaust Add Horsepower?


A catted downpipe will cost a little above $300 to buy and install, while an aftermarket exhaust system may cost more depending on the type of after-market exhaust system you will be getting. For aftermarket exhaust, you can expect to spend between the range of $150 to $2000 and incur further costs for labor.  


The catted downpipe is more expensive than the catless downpipes and even less expensive than the aftermarket exhaust system. The catted exhaust system will cost between $200 to $300 to install. The amount includes the cost of the parts and also the labor fee. 

Downpipe is considered one of the cheapest modifications that can be down to your exhaust system. 

READ MORE: Are Downpipes Worth It?


However, the exhaust will cost more to install. An aftermarket exhaust system will cost as low as $150 to a whopping $2000 with the exemption of labor fee. Although the cost of the exhaust depends on the type of modification you are going to have on the exhaust system. 

A full exhaust installation can cost up to $400 has a starting price to install and could climb up to $2000 or more depending on the vehicle and type of upgrade you would choose to be in the exhaust system, like a muffler. Adding mufflers to the exhaust system will cost you an extra $70 to $90. 

Installing an aftermarket exhaust system can be difficult, and time-consuming, this is why you need to trust an expert to install it for you.  

Engine Damage

The catted downpipe will not cause any damage to your engine system, but the catless downpipe could be bad for your engine. Also, the aftermarket exhaust system will not harm your engine system because it is meant to increase airflow and also reduce energy waste from the engine system. 


Catted downpipes are not harmful to the engine, they may throw codes and trigger the engine light, but it will not affect the engine of the car. The cause for the triggered engine, especially for the catted downpipes, is because it will affect the level of airflow through the engine system. 

Catted downpipe has a high-flow catalytic converter, and this converter will remove restriction and allow more exhaust air to pass through the exhaust system. This could trigger the exhaust engine light. 

Aftermarket Exhaust

The aftermarket exhaust system is also not harmful to the engine. The exhaust system serves to improve airflow and better exit exhaust gasses from the engine. These exhaust gasses could be harmful to the engine if not prosperity released from the engine system, and aftermarket exhausts allow for the proper release of the gasses.

The aftermarket exhaust system will not trigger the engine or throw codes. If it does, it means that something went wrong with the installation.


When it comes to sound, the catted will improve the engine’s sound significantly but not as much as the catless downpipe, which does not have any restriction by the catalytic converter. The aftermarket will also add to the sound of your engine, but the sound could be louder with a muffler delete. 


A catted downpipe will add to the sound of your engine, and this is because the downpipe has a high-flow converter that allows a better flow of exhaust gasses. However, the catted is not as loud as the catless downpipe. 

If you are looking for a downpipe with a more audible sound, then you can go for the catless downpipe. This downpipe does not have a catalytic converter and allows for a better flow of exhaust gasses. The rush of exhaust gasses will create a louder sound than the catted exhaust. 

Aftermarket Exhaust 

However, an aftermarket exhaust system will add to the sound of your engine, but it will not be as loud as the downpipes. Although by having a muffler delete done to the exhaust system, you can achieve a more audible and better sound with this upgrade.

Mufflers reduce the amount of noise that the car produces; once the muffler is removed, the vehicle can achieve a better and louder sound.  

RELATED ARTICLE: Are Bigger Exhaust Pipes Louder?


The downpipes are not legal in any state in the US and are sold for off-road use and tracking purposes. However, installing an aftermarket exhaust is legal in every state in the US. 

Downpipes are illegal in the US and are not road worthy, especially the catless downpipes. The catless downpipes do not have a catalytic converter, and it is easy for cars with catless downpipes to emit dangerous amounts of gasses. 

If you must use a downpipe, we recommend using a catted downpipe. The catted downpipes are not easy to sight and do not emit harmful gasses. It is because of the presence of the catalytic converter. 

Aftermarket Exhaust 

Also, the aftermarket exhaust system is legal for use in every control in the US, as long as the upgrade does not affect the catalytic converter or release smog after the installation. This is why we advise that you hire a professional to handle the installation of your aftermarket exhaust system. It will ensure that no important parts of the exhaust system are affected due to poor installation. 

RELATED ARTICLE: Downpipe 101: Horsepower, Engine Light, Sizing & Legality


When it comes to emission, getting a catless downpipe is a bad idea. However, the catted downpipe will pass for emission because it has its catalytic converter. Also, the exhaust system will not affect emission as long as the modification does not affect the catalytic converter. 


The catalytic converter is responsible for converting exhaust fumes into non-harmful fumes that will be safer for the environment. Catted downpipe has its catalytic converter, making it safe to use. However, Catless does not have, which makes it dangerous for use. 

Aftermarket Exhaust

The aftermarket exhaust does not affect emission because the converter is not affected during the modification. Its exhaust system will easily pass an emission test.  

Which is Better?

Both the downpipe and the aftermarket pipe are great modifications for your exhaust system, but the aftermarket exhaust system is considered better. This is because aftermarket  exhausts are legal in the US and downpipes are not, aftermarket exhaust can be louder than catted downpipes after making a few modifications, and many other reasons.  

Although the catted downpipes may cost less to install, the aftermarket is still better than the downpipe in many ways. The aftermarket exhaust gives your vehicle a better performance than the downpipe system. It is because the aftermarket exhaust allows for better airflow through the exhaust pipes. The pipes are bigger and can let out more exhaust gasses.

Also, the aftermarket exhaust is the safest exhaust modification for your car; it is legal; in all states in the US and does not affect emission. It also does not affect the performance of the engine system and does not trigger the check engine light.

Aftermarket exhaust also comes with so many parts you can add to your exhaust system just to get your desired result from your exhaust. Although these parts could add more to the price of the exhaust system, it is worth it.  

The catless downpipes are also great in many ways, safe for the road, and do not affect the engine when being in use, but we recommend that you get an aftermarket exhaust.  

Final Thoughts

It is important to note that the exhaust system is important for your vehicle. Before having any modification done, you must consider if it is suitable.

Although the catless downpipes may give you the desired performance, we do not advise you to get one; rather, you can get a catted downpipe or an aftermarket exhaust with an add-on that will bring your exhaust to your standard.

Chai WJ.

Chai WJ.

I am a car enthusiast and a passionate rider who loves to discover new places. Since the pandemic, I can't go to places and I started to blog and share information that I learned. I'm not easily distracted, I just... OMG, do I hear a Supra?

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