Does Muffler Affect Emission Test? (Aftermarket & Deleting)

By December 25, 2022Uncategorized

A muffler has nothing to do with the emission. If you change the muffler, you will pass the emission test if the replacement is done correctly. 

The muffler is the part of the exhaust system that deals with sound. There is a lot of misconception that changing the muffler will affect emissions. Personally, I have changed my muffler to a dual muffler. It did not affect my vehicle’s emissions, and I passed the emission test. 

This article will discuss what part of your vehicle the emission test inspection will take place. We will also look at the effect of the types of mufflers on emissions and how legal they are. The article will touch on muffler deletion, its effects on emission, and what effect changing the muffler has on emission. 

Also Read:

What’s Inspected During Emissions Testing?

During emission testing, two significant aspects are being inspected – they are the exhaust system and engine computer (ECM). 

The two aspects are responsible for the type of emission your vehicle produces. If any of these is faulty, it could affect the emission, and that way, you could fail an emission test. 

Below are what parts of the vehicle are inspected during an emission test. Let’s talk about each in more detail.

1. Engine computer 

The first inspection of the emission test is an OBD emission test done on the engine’s computer system, the Engine Control Module (ECM). They start by connecting your vehicle to a computer to perform that OBD test. 

The test is done to measure how efficient the ECM is. The ECM controls a large part of the vehicle and the engine. It also has a significant influence on the type of emission that the exhaust system will release. It monitors essential parts of the exhaust system, like the catalytic converter. 

Also, the ECM monitors and controls the transmission system, the engine’s general functioning, and the fuel system. The inspection of the ECM makes sure that the ECM is working as it should. 

It checks that the ECM meets up with the standard for the vehicle. It performs the responsibility of monitoring exhaust emissions and evaporative emissions. 

The test does more than check for emissions; it gives a good understanding of the vehicle’s general condition and if it is fit for driving. 

I cover more about the car’s computer in this article: Is Tuning Worth It: Costs, Risks & Power (Detailed Guide)

2. Gas analysis

This inspection measures the extent of specific substances in the exhaust gasses. The inspection is done through the tailpipe of the exhaust system. This gives more specific information about the vehicle’s emission than the OBD test.

The inspection will measure some specific gasses, which include the following. 

  1. Oxygen 
  2. Nitrogen Oxide 
  3. Carbon dioxide 
  4. Carbon monoxide 
  5. Hydrocarbon 

Usually, the test borders on analyzing just four of the gas substances mentioned above; in some states, nitrogen oxide testing is included; however, if you drive a diesel vehicle, the exhaust test analysis will be for soot. 

Many people get their gas analyzer, which can help them know what to get when going for an emission test, but it will not result in an emission sticker that shows that you pass the test.

Will Changing Muffler Fail Emission Test?

Your vehicle will pass the emission test if you change the muffler, as long as the replacement is done correctly and all errors detected by the ECM are solved.

Mufflers have the sole purpose of reducing the noise from exhaust gasses rushing through the pipes. The muffler has nothing to do with emission; unless it leaks, it might not pass emission. 

However, if changing the muffler affects the catalytic converter, and causes leaks or any other type of problem to the part of the exhausts, then you will not pass the emission test. 

The catalytic converter is part of the exhaust system that ensures that the gasses that come out of the exhaust pipe are pure from the most harmful substances that could be detrimental to living things. If faulty, it will allow your vehicle to fail emissions. 

Furthermore, it is doubtful that changing the muffler affects the catalytic converter. The distance between the catalytic converter and the muffler is quite much. Unless the person replacing the muffler is an amateur and does a poor job. 

Types Of Aftermarket Mufflers & How They Impact Emission Testing

There are different mufflers; some are stock mufflers, while others are high-end ones. Regardless of the type of muffler you use, it should not affect the vehicle’s emissions. If you want to know more about each type of muffler below, then check out this article: 5 Muffler Types Compared For Sound, Power & Mileage (Detailed)

1. Chambered muffler

Image of the internals of a muffler

Chambered muffler

A chambered muffler is one of the most commonly used muffler types. The muffler functions with a plate that allows the sound waves to bounce, resulting in them canceling each other.
A chambered muffler does not affect the emission of a vehicle. However, it will influence your vehicle’s sound, making it loud but not too loud. 

2. Turbo Muffler

Turbo mufflers

Turbo muffler

Turbo muffler is another type of exhaust muffler that uses an S-shaped tube. The pipe is equipped with fiberglass packing, absorbing sound waves as the gasses pass through the tube. 

A good thing about a turbo muffler is that it does not affect emissions at all and provides less gas restriction.

3. Straight Through Muffler

Glasspack mufflers

Straight through muffler

The straight-through muffler is a type of muffler that provides a louder sound when compared to other types of the muffler. When you think of a muffler that provides better horsepower and sound, this is the one for you. It can add up to 5 to 15% horsepower to your vehicle. 

A significant disadvantage of this type of muffler is that it is not legal in most parts of the USA because of the sound. It can be too loud and draws too much attention. Straight through the muffler will not affect the gas emission. 

4. Resonator

The resonator is used together with a muffler, and it is used to eliminate drones and humming noise. It does not serve as a replacement for a muffler; instead, it works with a muffler. 

If used without a muffler, it will cause the vehicle to become too loud. Once this happens, the modification will become illegal because it goes against the maximum noise a vehicle can produce. 

The resonator does not affect gas emissions in any way, and as long as it is used with a muffler, it is legal to use anywhere. 

5. Exhaust Baffle

The exhaust baffle is used to reduce the exhaust sound. It is installed in the muffler or exit tip. Its only function is to provide more silent sound. An exhaust baffle also will not impact emission.

Will Muffler Delete Fail Emission Test? 

A muffler delete will not affect the emission and will pass the emission test. However, muffler deletion is not legal in many states as it is required that every vehicle have a muffler. Also, a muffler delete can be too loud and will draw the attention of the authorities. 

Muffler delete removes the muffler in your vehicle and replaces it with a straight exhaust pipe. It is mainly done to improve exhaust gas flow and make the vehicle louder. 

The sound of a muffler delete is intimidating and attracts much attention. It is the reason why it is illegal in all the states in the US. 

As much as the muffler is not legal in most states, it will pass the emission test; removing your vehicle’s muffler does not have anything to do with your vehicle’s emission. 

I cover muffler delete extensively in these articles:


When installing an aftermarket exhaust product, it is essential to consider the effect on emission and if it will pass an emission test. Many people do not consider this; before installing the part. Fortunately, muffler aftermarket products will pass emissions because the muffler does not affect the vehicle’s emission in any way. However, the type of muffler you get will affect your vehicle’s sound. 

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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