Exhaust Vs Muffler In Detail: Horsepower, Sound & Cost

By August 10, 2021Exhaust, Muffler

Aftermarket mufflers work by providing lesser sound suppression – this makes your car sound louder and more aggressive but don’t expect any horsepower gain. 

On the other hand, aftermarket exhausts are significantly less restrictive and also come with an aftermarket muffler –  which means they improve both horsepower and sound. 

Choosing between an exhaust and muffler as your first mod could be difficult (at least it was for me). Both of them supposedly make your car sound better and faster – but which one is better? 

As someone who has installed both and tried out different types, I can tell you an exhaust is always a better choice if you want both power and sound. 

In this article, I am going to compare exhaust vs muffler in detail. This covers everything you need to know before deciding which one to get:

  1. Horsepower gain
  2. Backpressure
  3. Exhaust velocity
  4. Sound improvement
  5. Tuning
  6. Are they legal?
  7. Gas mileage improvement 
  8. Cost
  9. Installation

That’s a lot of things… But don’t worry. I will keep it straight forward and easy to understand. Shall we? 

To understand their functionalities, we must first briefly understand how your car engine works.

How Combustion Engine Works

Your car engine is a combustion engine – it uses a mixture of air and fuel to create combustion and deliver power to the wheels. 

Fuel is injected into the combustion chamber from the fuel tank. Whereas air is sucked from the outside via an intake. 

During a combustion, both power and exhaust gases are produced. These exhaust gases must leave the combustion chamber as quickly as possible to allow more space for air in the next combustion. 

If the exhaust gases do not leave the combustion chamber in time, the next combustion will be weak because there’s not enough space for more air to enter. 

anatomy of combustion chamber
Air enters combustion chamber from intake
Fuel enters combustion chamber via fuel injector
Combustion and exhaust gases are created. Exhaust gases leave through exhaust valve and into the exhaust system

How Does Exhaust Work

An exhaust system is responsible for getting exhaust gases out of the combustion chamber.  Aftermarket exhausts are less restrictive – they allow exhaust gases to travel much quickly. 

Which means more vacant spaces in the combustion chamber, allowing more air to enter – resulting in bigger combustion and more horsepower. 

Keep in mind, an exhaust system is made of multiple components: headers, catalytic converters and mufflers. 

When getting an exhaust system, it most likely also comes with CATs and mufflers (depending on the type). This is why exhaust is more expensive than just a muffler. More on this later.

Image of header back exhaust

Aftermarket exhaust

How Does Muffler Work

A muffler is responsible for suppressing noise coming from the combustion engine. It works by bouncing sound waves against each other – causing them to cancel out.

Earlier I told you that a combustion engine delivers power by mixing air and fuel to create combustion. This combustion is a small explosion that produces big sound waves. 

Just like the exhaust gases, sound waves travel through the exhaust system to outside the car where you eventually hear it. 

The inside of a stock muffler is made of chambered plates – designed and positioned specifically to bounce off sound waves, where they collide into each other and cancel out. 

Image of the internals of a muffler

Chambered muffler bounce sound waves into each other – causing them to cancel out

Aftermarket mufflers make your car sound louder by reducing the number of plates or even removing them altogether and use a different type of sound suppression like fiberglass.

Aftermarket mufflers are very effective. If all you want is a louder car, then a cheaper aftermarket muffler is the better option (compared to exhaust). 

Exhaust Vs Muffler

Exhaust Muffler
Horsepower Gain 30hp 5hp
Effect Exhaust Backpressure Yes Yes
Effect Exhaust Velocity Yes No
Sound Improvement Yes Yes
Tune Required Yes No
Legal Yes  Yes
Void Warranty Partially Partially
Improve Gas Mileage  No No
Cost ~$600  ~$100
Installation Difficulty Medium Low


Horsepower Gain: Exhaust Vs Muffler

Aftermarket exhaust can provide more horsepower than a muffler. The actual gain depends on your engine size.

But on average, an exhaust can give you 30 horsepower (with tuning), whereas a muffler 0-5 horsepower gain. 

An aftermarket exhaust provides more horsepower because they replace more significant components like CATs, mufflers and the entire exhaust piping. 

I don’t expect a muffler alone to gain you any horsepower. Some people say they gain 5 horsepower. But to be honest, 5 horsepower is insignificant when it comes to cars. 

If you are serious about power, an aftermarket exhaust system could be a great first mod. 


Exhaust Backpressure: Exhaust Vs Muffler

Aftermarket exhausts can significantly reduce exhaust backpressure because all the components that come with aftermarket exhausts are designed to be less restrictive. 

Muffler on the other hand, does reduce some backpressure but it’s not significant enough to be noticeable. 

In case you don’t know, exhaust backpressure means how much pressure is coming from the exhaust system.

High backpressure is always bad for performance because backpressure prevents exhaust gases from leaving the combustion chamber into the exhaust system. 

Remember, air particles like exhaust gases always want to travel from a high pressure area to a lower pressure area. If pressure from the exhaust system is high, it prevents exhaust gases from flowing to it. 


Sound Improvement: Exhaust Vs Muffler

Both aftermarket exhaust and muffler can provide significant sound improvement. The loudness and exhaust notes depend on which model you get. 

The sound of your car is dictated mostly by the muffler you use. 

Keep in mind that an aftermarket exhaust also comes with a muffler. Which means, both exhaust and muffler can provide you with the same sound improvement. It all depends on the model you get. 

Some mufflers are created to be extremely loud while others not so much – this is personal preference. 

I recommend getting a muffler that’s louder than stock but not so loud that it’s deafening. Loud mufflers are fun and exciting for the first week. After that, believe me – it gets annoying real quick. 

If all you want is sound improvement, a muffler alone is good enough. It’s cheaper and easier to install. 

If you want both sound and horsepower, then you should look for an exhaust. Each exhaust equips a different muffler. Make sure you hear before-and-after videos on YouTube of forums before you decide on one. 

I am gonna talk about my recommended muffler and exhaust later. 

Related Article: 5 Ways To Make Your Car Louder For Cheap

Tune Required: Exhaust Vs Muffler

Aftermarket exhaust requires a tune to prevent a lean engine and give you the most horsepower. On the other hand, a muffler does not require any tuning to work. 

Tuning is required for aftermarket exhaust to fix the lean air/fuel mixture. Keep in mind that an aftermarket exhaust ultimately provides more air in the combustion chamber. 

However, more air with the same amount of injected fuel will make your engine run lean. 

With tuning, you can configure your car to inject more fuel and obtain the right air/fuel ratio. Only then will you gain the maximum HP. 

On the other hand, a muffler does not require any tuning to work. An aftermarket muffler does not create any change that’s significant enough to tweak the air/fuel ratio. 

Related Article: How Much HP Can You Gain From Dyno Tune?


Are They Legal: Exhaust Vs Muffler

Depending on the type you get, both aftermarket exhausts and mufflers can be installed legally. Just make sure it’s not too loud and can pass the smog inspection. 

Aftermarket mods like exhaust or muffler are not legal if it’s too loud or doesn’t pass the smog inspection. 

The actual law differs from each state or location. It’s best to check with your local law before getting one – they should have the actual decibels that you need to follow. 

It’s also a good idea to ask the shop that sells you the aftermarket mod – they should know better. 

Generally for sound, getting an aftermarket mod that changes the exhaust note and makes it slightly louder is good enough. Your car becomes more aggressive and no troubles with the law.

Remember, a muffler or exhaust that’s too loud is only fun for a week. After that it’s annoying and deafening. Trust me, I have been there. Make sure to test out the sound while inside and outside the car. 

As for smog inspection, if the exhaust equips complete catalytic converters (CAT), then you should be good. You should also check if the CAT is less restrictive – and if yes, how less restrictive are they?

Check with the shop that sells you the exhaust – they should know better. 


Void Warranty: Exhaust Vs Muffler

Both exhaust and muffler partially void the warranty of your car. Specifically, by installing exhaust or muffler, you most likely void the warranty of your exhaust, CAT and muffler.

Due to the Magnusson Moss Warranty act, dealers cannot void your warranty with misleading warranty clauses.

To actually void your warranty, dealers must prove how your aftermarket mod is a direct cause to the problem. And even if they can do that, dealers can only void warranty for certain parts (not the whole car).

As a rule of thumb, if you install an aftermarket muffler or muffler, you will void the warranty of the relevant parts like exhaust systems, mufflers and CATs. 

This sometimes depends on your relationship with the dealer as well. Some dealers may give you a pass and not void the warranty when you need it.

Gas Mileage: Exhaust Vs Muffler

Both aftermarket exhaust and muffler do not improve gas mileage. These mods are designed with horsepower and sound in mind. 

You generally don’t improve gas mileage by installing performance mods. Exhausts and mufflers are no exception. 

Some enthusiasts argue that aftermarket exhaust can improve gas mileage because they provide more air in the combustion chamber – allowing injected fuel to be fully utilized. 

This is not true, especially when we consider that tuning for exhaust means injecting more fuel in the combustion chamber to make use of the extra air. 

More air and the same amount of fuel does not improve gas mileage. That simply makes your car run lean and overheat. 

If you care about gas mileage, there are many other things you can do:

  1. Check tire pressure
  2. Remove unnecessary baggage in car 
  3. Tune your car for gas mileage 
  4. Avoid revving up too often


Cost & Installation: Exhaust Vs Muffler

Aftermarket exhaust is significantly more expensive than a muffler. This is because aftermarket exhaust is larger and contains much more components.

The actual cost depends on your car model and year. For example, a Flowmaster cat-back exhaust for a Subaru BRZ costs about $600, whereas the muffler costs about $100 (excluding installation and tuning fee).

You need to make sure you are checking out mods that suit your car model and year. This is important. Getting mods that won’t fit your car is frustrating. 

If you are thinking of getting a muffler or exhaust, there are many things you need to consider. For example, the brand, the piping diameter, material and much more. 

I created these articles to help you identify the things you need to watch out for when getting mufflers / exhausts. In there, I also recommend exactly which brand is my go to.

  1. Best Aftermarket Exhaust: Which To Get & What To Look For?
  2. Best Performance Muffler: Which To Get  & What To Look For?

As for installation, it’s quite common to first get the mod you want and then bring it over to a mechanic shop for installation. 

If you are handy, you can always find YouTube videos that show you how to install these exhausts or mufflers. 

Generally, installing a muffler or exhaust should be just a matter of screwing and unscrewing bolts – if you got the right one that fits your car. Otherwise, you may need to look into custom welding and knocking jobs. 


Should You Install Exhaust Or Muffler?

Install an aftermarket exhaust if you have the budget and are looking for horsepower and sound. Install a muffler if you only want the sound. 

If you are an enthusiast, you should definitely install these mods. I guarantee, sooner or later you are going to do it anyway. It’s just a matter of which one first.

For exhaust, you need to buy the exhaust, install it and tune it. The costs for all of these can stack up real quick.

Which is why personally, I recommend installing a muffler first as your first mod, then work your way up to the cold air intake, air filters, exhausts and headers. Combine it with a tune and your car should fly. 

Ifandi L.

Ifandi L.

Passionate about everything mechanical. Ifandi has been involved with motorcycles and cars since the old days - in his family's auto parts shop. Want to keep in touch? Scream "STRAIGHT PIPEEEEE" at the top of your lungs and Ifandi will show up.

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