Some people who equip aftermarket exhausts notice their exhausts getting louder over some time. Does it really happen? Or is it just in their head?
Long story short, aftermarket exhausts that equip mufflers with fiberglass packing will get louder over time – this is known as “muffler break-in”. Fiberglass packings are used to absorb sound waves in the exhaust pipe. With time, these glasspacks can wear out and get broken – reducing the muffling and making the exhaust sound louder.
This only happens to mufflers that use glasspacks to absorb sound. Common mufflers like chambered mufflers will not experience break-in.
Now that’s out of the way, let’s go into more details about mufflers, muffler-break ins and what other factors can cause exhaust to sound louder over time.
Recap: What’s The Function Of Muffler?
Let’s recap this topic for the beginner enthusiasts. If this is not you, just skip to the next section 🙂
Mufflers are equipped in car exhausts to silence engine sound. You see, car engines generate power by creating combustion in the combustion chamber. Combustions are controlled explosions that generate exhaust gases and huge sound waves.
These exhaust gases and sound waves then travel through the exhaust pipe and exit the car. Without any muffler, the combustion noise would be extremely loud – making the car undesirable to the mass market. And not to mention, states like California have strict regulations to ensure your engine noise is below a certain level. If you are interested, Here’s a list of laws regarding exhaust noise in different states.
Different Types Of Mufflers
Now that we know what a muffler is, let’s discuss different types of mufflers. This is important because only some types of mufflers will get louder over time – AKA “muffler break-in”.
1. Chambered Mufflers
Chambered mufflers are the most common types of mufflers. Stock mufflers and a lot of aftermarket mufflers are chambered mufflers.
If you cut open a chambered muffler, you will see that it’s sectioned into chambers – each separated by a metal plating. Chambered mufflers use these metal platings to bounce sound waves and reverse them into each other – causing them to cancel out.
Look at the diagram below to see what I mean. Follow the numbered markings.
Chambered mufflers will not cause exhaust sound to be louder over time. It’s because the metals used in chambered mufflers are durable and will not wear out even after long usage. This is why you often see aftermarket chambered mufflers to have a long warranty period.
2. Straight-through Mufflers (Has Break-In)
Straight-through mufflers are straight hollow tubes with a layer of fiberglass packing on the walls to absorb sound waves as they pass through. It’s also known as a glasspack muffler.
Straight-through mufflers are more performance-oriented in nature. The idea is to allow exhaust gases to flow through as easy as possible. Thus, reducing the pressure in the exhaust pipe (backpressure).
Less pressure in the exhaust pipe means that exhaust gases can leave the combustion chamber quickly and allow more oxygen to enter for the next combustion cycles – resulting in bigger combustion and more power.
Straight-through aim to improve your car performance and will also make your exhaust sound super loud. The only downside is that the fiberglass packing could wear out as you drive the car. AKA muffler break-in.
Broken fiberglass packings will reduce muffling and cause your exhaust to sound even louder. You cannot prevent this break-in. Either embrace the sound change or switch to chambered mufflers.
3. Turbo Mufflers (Has Break-In)
Turbo mufflers also use fiberglass packing on the walls to absorb sound waves. However, turbo mufflers are much quieter than straight-through and will not provide any performance benefit. Turbo mufflers have nothing to do with turbochargers and can be installed on cars without turbochargers.
If you cut open a turbo muffler, you will see that it has an S-shaped pathing. This shape allows sound waves to pass through as much fiberglass as possible and maximize the sound waves absorption.
Turbo mufflers will keep your exhaust sound relatively quiet at the cost of “performance”. A lot of people argue that turbo mufflers are very restrictive and will decrease performance due to the backpressure created. I would say the impact is very small and you should not worry about it.
Same as the straight-through, turbo mufflers will also experience a break-in. As time passes, the glass packs will wear out and reduce its muffling.
Reasons Why Exhausts Get Louder
1. Muffler Break-In
This is the most common reason for mufflers getting louder. Some types of mufflers like straight-through mufflers or turbo mufflers equip a layer of fiberglass packing around their inner walls to absorb sound waves as they pass through.
With time, these fiberglass packs get worn out and can be broken. As a result, the muffling effect is reduced – causing your exhaust sound to be louder. This is very common and not something you should worry about.
Actually, this is inevitable for mufflers that use glass packs. If you don’t want to experience this “break-in”, then look into chambered mufflers instead. I recommend looking into the Flowmaster Super 40 chambered muffler. I cover why in this article.
2. Car Warm Up
If you notice that your car idle is louder during a cold start, then that’s perfectly normal. During a cold start, a car needs to warm up its components into ideal working temperature and get engine oil to run through the engine.
This means more airflow required = higher idling = more exhaust gases = more noise. Don’t worry about this – after your car is warmed, the idling will go back down. Probably after 15 minutes or so.
3. Colder Temperature
You might also notice that your exhaust sounds louder when driving under cold weather like during winter. Why is that?
If you don’t already know, your car’s computer maintains a balanced ratio of air (oxygen) to fuel. The quantity of fuel injected depends on the air flowing into the engine. More air (oxygen) = more fuel to be injected, resulting in higher performance.
During cold weather, the air in the surrounding is colder. Colder air is more dense and it contains more oxygen. This means the same amount of airflow contains more oxygen than before. Your car’s computer notices the increase in oxygen and will inject more fuel. This causes bigger combustions which result in more noise and more performance.
If you are confused, take a look at this article – Do cold Air Intakes Add Horsepower?. I cover the topic of colder air and increased performance in more detail.
How Much Louder Will Exhausts Get After Break-In?
Again, this depends on how much of the glass packs are worn out. The more worn out it is, the louder the exhaust becomes. The initial break-in sound will be minimal – you will probably hear a slightly deeper growl and more aggressive sound.
After a long period like a year – is where you will hear a significant change in sound. Here’s a YouTube video that compares the exhaust noise before and after the muffler break-in. (One year apart).
How Long Before Muffler Break-In?
This depends on how much you drive and how you drive. If you drive often and you are the aggressive driver that likes to rev up, then probably a week or two. If you drive regularly and do not rev up, then probably a month.
You need to hear the sound when you rev up. Simply listening to the break-in sound when idling won’t give you much.
Other Ways To Make Exhausts Louder
If you are looking for a consistent sound, then I recommend you get chambered mufflers or other mods like cold air intake or resonator exhaust tips. Heck, you could even drill some holes on your exhaust if you are really on a budget.
Here’s an article I wrote about the 5 ways to make your car louder for cheap.