You may probably have encountered one of those pimped out cars slowly coast by in front of you, only to suddenly roar with a heart thumping growl as it takes on the length of road ahead, leaving you with a trail of dust and a pounding heartbeat. Perhaps you may have witnessed a car started and revved up with a mighty and low-pitched roar that sounds so aggressive and angry in contrast to the smug smirk of the driver.
Noise to others while music to some, this sound is generated by that small tank-like car part that you can see under the belly of your car, and that part is called a muffler.
Patented during the late 1800's by Milton and Marshall Reeves, mufflers (or silencers in some European countries) have been an essential part of any car exhaust system, mainly to dampen the sounds generated by car engines. One way of knowing how car engines sound like without them is to compare it with race cars, that typically have no mufflers in their exhaust systems. These mufflers are designed nowadays with certain specifications to follow sound pollution ordinances, especially in urban areas.
Car mufflers are simple, yet fully functional devices which are most often located at the rear of your vehicle. It is hard to miss it as the tailpipe where the exhaust comes out is the landmark for the muffler. Just a few inches further is where you would see the muffler - an oversized shaped flask in most cases but may take other custom form to suit the car shape design. Some car configurations may already expose a little bit of the muffler at the back of the car, just being behind the tailpipe. Others, such as sport cars may have their muffler system hosted further within. Heavy duty trucks and pickups may have their mufflers totally exposed but still placed in a discrete area.
Usually the muffler is synonymously associated with the exhaust pipes because they are just adjacent to each other and directly connected. Stock mufflers that come with cars have the tailpipe and muffler as one continuous item. Aftermarket models, especially those bought with certain ratings and custom designs in mind, are sold either as a whole set with a tail pipe or as a single separate item, leaving the car owner with the freedom to choose a custom tail pipe as well.
Part of A whole System
Mufflers are just one of the parts(yet extremely important) in a much bigger and complex exhaust system. Serving its own purpose of generally sound dampening of engine combustion noise, other parts have their own specific design and functions.
As a whole, the exhaust system serves three main things: to dampen combustion noise, to convert toxic fumes from engine combustion into manageable output, and to vent out these fumes out effectively.
Starting with the most immediate part of the exhaust system, the exhaust manifold and header is the part responsible for collecting all the exhaust from the combustion as well as the sound being generated. You may see it as you open the trunk and look at the engine - as a collective form of pipes that run from the valves and into a single pipe. The header is referred to the pipe that emanates from each cylinder of the engine while the manifold is the area where each header converges.
The mid-pipe is the area that follows the manifold. This is usually the longest part in automotive exhaust systems as they include the catalytic converter, and main exhaust piping. Catalytic converters are special devices that collect the toxic fumes from engine combustion such as the carbon monoxide (CO), nitrous oxides (NOx), and unburned hydrocarbons, and turn them into carbon dioxide (CO2), nitrogen (N2), and water (H2O). This device is responsible for keeping the toxic fumes from finding their way into the passenger cabin and posing a health threat.
The end portion of the exhaust system is the end-pipe that is composed of the muffler and the tailpipe. Basically, the task of this area is to convert the explosive noise created into a relatively soothing whir and dissipate it via the tailpipe.
The Science Behind Mufflers
Throughout the whole engine to exhaust systems, mechanical and chemical concepts govern them. However, the muffler takes on a completely different approach in handling car mechanics - it takes up physics and sound dynamics.
You may wonder why mufflers are usually shaped in that flask like form. It actually serves two main purposes:
First, the flask shape (or in other cases customized to fit the shape of the car's chassis) acts as a chamber to collect the accumulated sounds, thereby providing a lower pitch than the traveling sound within the mid-pipe. Second, the series of pipes inside the muffler is designed in such a way that the traveling sound is redirected back within the chamber, and positioned so that the back waves would be the same as the incoming ones. The resulting conflict of these sound waves cancels each other significantly, leaving a much lower and manageable sound to the drivers ear.
Opening up any stock muffler, you would be able to see multi-layered sheets of either aluminum or stainless steel as the main body, with the three internal pipes having holes in the middle area. These holes serve as mini exhausts for the pressure from the mid-pipe to escape and create a 'barrier' for the main sound wave. The mid-pipe goes into the center of the muffler and arches to one side within. On the other side, a separate and independent pipe vents out into the tail pipe. This creates a semi balanced sound wave system within the muffler.
Even if the sound of non-muffler exhaust systems such as those found in race cars seem exciting and fun, having the same non-muffler configuration in your day-to-day vehicle in magnitudes of the tens or hundreds of thousands in urban areas would be catastrophic to the noise it would generate and your neighbourhood will certainly hate you for that.
However, there is also one major drawback with the use of mufflers which is its affect on overall speed of your car. Basically, mufflers lessen the horsepower output of the engine. One indispensable concept in car exhaust systems is that the same pipe is traveled by the resulting combustion force, as well as the sound wave, which also is part of the force generated. Having to 'dampen' one in this manner, also dampens the resultant force of the other, thereby creating less power for the car. This is the very reason why race cars have more horsepower but are also generally noisier. Nevertheless, commercial automobiles don't really need that extra horsepower as they usually have enough torque already.
Like any other car component, mufflers also tend to wear out over time. Factors that lead to its wear and tear are from the harsh environment both inside and outside, poor maintenance, bumps and dents, and unsecured placements.
Even if it is made of metal, the most common reason for muffler replacement is rust. Even stainless steel eventually succumbs to the reality of rust formation. Given the fact that carbon deposits thicken inside, plus the presence of condensation from cold start-ups, and with the constant passage of oxygen based compounds, rust is prone to form within.
As with the outside, the environment such as the atmosphere, water splashes, and other corrosive elements it is exposed to also pose a great risk in rust formation. Driving around flooded areas in this manner calls for an immediate checkup as possible external elements may find its way into the muffler, thereby hastening the damage process.
Even seemingly harmless bumps under the chassis due to road bumps, stones or potholes may also prove damaging in the long run. This may lead to inefficient exhaust, loose fixtures, and eventual worsened physical damage to the muffler.
One way to determine if you may have trouble with your muffler is by getting the feel of its sound when you rev up your engine. While still in neutral gear and with the engine running, try to rev it up slowly and see how the sound of the care engine differs from the usual. If you hear rattling somewhere behind and underneath your car, it may be a loose fixture of your exhaust pipe or muffler. If the whirring sound becomes louder or throatier beyond the usual, it may indicate a damaged, defective, or clogged muffler. In any case, it is a good idea to have it checked with your local auto shop for experienced automotive advice.
Expect to dole out about a $100 to $200 for an after market muffler unit including labour. For custom and specialized mufflers, you may expect to burn around another couple of hundred bucks, but with the satisfaction of that throaty VROOM! That would surely catch any wandering ears nearby.
You do not have to worry if your muffler starts to fail after around 4 to 5 years, especially with the aluminum type ones. They usally keep going even with a small malfunction; you only get to hear loud, unwelcome sounds, and disapproving stares from passersby. Changing mufflers is relatively quick when serviced in, and would not necessarily cost a leg and an arm for generic types.
How to replace muffler yourself
Watch this educational video on how to replace muffler yourself and save on repair and replacement costs: