Understanding Mustang Exhaust Systems

There is no doubt that buying parts for your Mustang's exhaust can be confusing. There are so many brands to choose from, and knowing which parts will work together is crucial to having an exhaust system that is both efficient and great sounding. To make it easier, we’re going to break down the entire system into three main sections: manifolds/headers, mid-pipes, and cat-backs.

It's important to note that 2015+ Mustangs have a slightly different exhaust configuration than your standard Mustang. Looking under an S550, you'll see a suitcase looking thing where your mid-pipe union usually is. This "suitcase" is a resonator, designed to quiet down the exhaust. They come from the factory with an H-style mid-pipe, which gives the system a deep style tone. However, most owners prefer to change their exhausts to their own liking, primarily with an axle back exhaust and a mid-pipe. The whole system weighs in around 70 lbs.

A Mustang's exhaust manifold is connected to the exhaust ports of the engine. They funnel the exhaust gases from the cylinders into a single exhaust passage (the mid-pipe). You will hear manifolds referred to as headers. While they perform the same function, they are not exactly the same. The exhaust manifolds are the factory headers. Usually, they have several holes that merge into a common chamber.

The aftermarket manifolds, or headers, generally have tubes that curve to join the exhaust ports to the pipe. Shorty headers are designed to bolt into the factory manifold location. Long tube headers are usually made for racing applications. Equal length headers can be either shorty or long tube, and the equal length tubes allow for slightly better exhaust flow. It is the curves that make headers a popular modification. This allows the gases to gently slide into the pipe, rather than slamming through the ports.

Those of you who live in emissions restrictive states will be forced to keep the stock manifolds since long tube headers often times will not pass emissions testing. Unfortunately for EcoBoost owners, the EcoBoost exhaust manifold is cast into the cylinder head and can’t be replaced. Since the EcoBoost is a turbo motor, it has a special exhaust manifold that re-circulates the exhaust gasses to the hot side of the turbo before going out the tailpipes. Because of the constricted space to do this, the OEM piece is nearly efficient as one can get, and thus no aftermarket designs have yet surfaced

Shorty Headers vs the Stock Manifold: Shorties are equivalent in size to stock exhaust manifolds. They work with stock mid-pipes as well as standard length aftermarket mid-pipes. Shorty headers are ideal for turbocharged Mustangs and do provide more horsepower and torque than the stock manifolds, but not quite as much as long tubes. Shorty headers are also good for street builds by increasing horsepower without sacrificing low end torque.

Long Tubes vs the Stock Manifold: Long tube headers do not work with stock mid-pipes because they are too long to bolt up to the factory mid-pipe. Long tube headers require a "shorty" mid-pipe to maintain a consistent exhaust length. Long tube headers and full-length headers are the same thing. Long tubes generally provide more horsepower and torque than shorty headers, but cannot be used with turbocharged motors.

All Mustang exhausts have a mid-pipe. A mid-pipe is where gases go when they leave the manifold. GT mid-pipes are different than V6 mid-pipes.

• GT Mustangs: Come stock with a pipe that has an H-formation (H-Pipe)
• V6 Mustangs: Come stock with a pipe that has a Y-formation (Y-pipe)
• Some aftermarket mid-pipes come in an X-formation and are called X-pipes
• 2015+ Mustang mid-pipes feature a resonator (sometimes called a suitcase) adding weight (total system weight is about 7 lbs)

All stock mid-pipes come with catalytic converters, or "cats". Cats remove the contaminants from the exhaust, making them emissions friendly. Aftermarket mid-pipes that are meant to be used off-road or for racing don't have catalytic converters, and are called "off-road H- or X-pipes". Off-road mid-pipes aren't meant for street use and, depending on your state's emissions laws, may not pass inspection. By removing the restrictive factory catalytic converters from the exhaust, your Mustang is able to produce more horsepower and torque, making such a mid-pipe perfect for race applications such as track and drag racing. In general, most aftermarket catted mid-pipes feature high flow catalytic converters which provide a small bump in horsepower and torque over the restrictive stock factory cats, but they keep your Mustang emissions legal.

• Off-road mid-pipes do not include catalytic converters
• Without catalytic converters, your Mustang will produce more horsepower and torque
• Malfunction Indicator Light Eliminator—MILs—can be purchased to turn off a faulty O2 sensor check engine light

With about two hours’ worth of work, you can replace the restrictive factory mid-pipe, with a free flowing off-road mid-pipe. Along with increased exhaust flow, you’ll get a more aggressive and louder sounding car. One thing to be aware of though, is removing the cats will also result in a stronger exhaust smell and the smell of unburned fuel which is removed by the cats. It is also illegal in all 50 states, so you run the risk of getting a fine if a law enforcement officer chooses to check for them.

Almost every mid-pipe AmericanMuscle carries are standard length. They will work with stock exhaust setups as well as aftermarket headers and cat-backs. We also carry several shorty mid-pipes, which are used most often in racing applications. These pipes will only work with aftermarket long tube headers. When buying aftermarket long tube headers and short mid-pipes, it is recommended that you stay with the same brand for both parts. In short, mid-pipes can do the following:

• Changing the pitch of the exhaust note
• Giving the car more horsepower and torque
• Removing or replacing the stock catalytic converters with aftermarket setups
• Easy fitment in combination with long tube or short tube header

What's a cat-back? The cat-back is the system that bolts on behind the catalytic converters. The assembly contains the mufflers and the tailpipes. This is the final destination of the nasty gases from your engine.

With the EcoBoost, the downpipe connects to a resonator which then splits the exhaust into a dual setup, each side having its own muffler before finally venting into the atmosphere. Aftermarket systems ditch the resonator, replacing it with a Y-assembly and replace the stock mufflers with higher flowing, louder units. Certain cat-back systems may use straight through mufflers, which typically flow the best. While these mufflers undoubtedly sound amazing, straight through style mufflers may be illegal in some states (so be careful!).

What's an axle-back? You may have seen the term “axle-back” mentioned in your research about exhaust systems. Axle-back systems are still the last piece of the exhaust system. They differ from a cat-back because they bolt up behind the mufflers. An axle-back exhaust is essentially the muffler, and begins at the rear axle and runs out the back of your Mustang. Axle-backs are the last part of your exhaust system and have a large effect on how your Mustang sounds. Axle-back exhausts deliver very small if any power gains (less than 10 HP) and are primarily a sound upgrade for your Mustang.

Did you say axle-back? – What’s nice about the 2005 Mustangs is it allows you to just replace your pipes from the axle, back. Though you can never go wrong with a new aftermarket cat-back.

Cat-Back Exhaust Summary

• Add small amounts of power (5-15 HP on average)
• Go from the catalytic converter all the way back
• Are louder than axle-backs, but not as loud as long tube headers
• Offer deep, full exhaust notes without requiring a tune

Axle-Back Exhaust Summary

• Typically don't add much power (less than 5 HP on average)
• Go from the rear axle to the back of the car
• Big improvement over stock, but not as loud as doing a cat-back or headers
• Different systems offer different exhaust notes, from more low-key rumble to waking your neighbors loud

Mustang axle-back systems get their sound based off of:

•    The overall design/shape
•    If there is a resonator or if it is removed
•    The internal construction/chambering or if anything is baffling/impeding the flow
•    The materials used to insulate it

The largest determining factor of what an axle-back will sound like is based on its style or type.

There are several types of Mustang mufflers/axle-backs that include:

•    Muffler deletes
•    Chambered
•    Varitune/valve controlled    
•    Straight-through
•    Race oriented/style

Each style of axle-back looks, functions, and sounds different from the other as their design will give you your exhaust note.

Muffler delete axle-back systems remove the muffler from the equation, leaving you with free flowing straight through piping. Muffler delete axle-backs have a very aggressive and somewhat raspy exhaust note that will allow your exhaust to go unchecked and uninhibited. A Muffler delete Mustang axle-back is for enthusiasts who want to have one of the loudest Mustangs around, one that can heard long before it is seen.

Chambered axle-backs have either an open chamber design or a multiple chamber design. In general, chambered axle-back exhausts tend to be more gurgly, yet deep in tone with an aggressive finish. Open chambered axle-backs tend to have more exhaust pops/crackling then multiple chambered axle-backs. Chambered axle-backs are great for daily drivers that are looking for a deeper and fuller exhaust note that sounds great at wide open throttle and not too loud at cruising speeds.

Valve controlled exhaust systems use a switch or remote control to open up an electronic butterfly valve in the axle-back to change it from a chambered setup to a straight-through setup. These are ideal for people who are holding off on exhaust upgrades because they are trying to avoid offending the neighborhood. You get the best of both worlds by being able to cruise at a reasonable volume when you want to or sound like a racecar with the press of a button.

Straight-through Mustang axle-backs are similar to the shape of chambered axle-backs, but internally there is nothing in there to baffle the sound. Straight-through axle-backs are fairly loud and aggressive and definitely for the Mustang enthusiast who wants to be noticed anytime the step on the throttle.

By far, your loudest option for a Mustang axle-back system is one that uses a race style orientation. Race style exhausts are similar to muffler deletes and straight-through exhausts, but they tend to have a much raspier and loud exhaust note that crackles every time you let off the throttle.

The best material for a Mustang axle-back to be constructed from is 304 stainless steel as it is incredibly resistant to corrosion and is much stronger than 409 stainless steel. 409 grade stainless steel is perfectly suitable for any axle-back system, just be aware that it is more likely to rust and is constructed from a softer steel.

An incredibly popular axle-back style that was introduced by the 2013 Shelby GT500 is the quad tipped axle-back. Quad tipped Mustang exhaust systems can be found on every type of axle-back style and generally don’t provide much of a sound difference. In order to put one on your non-Shelby Mustang, you will need to replace or DIY customize the rear valance to make space for the extra exhaust tip.

A very common question when modding your Mustang is whether or not the mod will require a new tune. Upgrading your axle-back will not require you to reflash your Mustang’s computer. You can just bolt those new beauties on and enjoy your new exhaust sound and performance.

Sometime in 2007, Ford changed the style of exhaust hangers used to install the stock exhaust on the 2007 S197 Mustang. They switched from a "rubber and steel" hanger design to an "all rubber" hanger, which will not work correctly with the aftermarket exhaust systems on the produced today. You will want to visually check your exhaust prior to ordering any new exhaust to determine whether or not you will need this optional rubber and steel hanger kit. The SR Performance 304 Stainless Steel Exhaust Hanger Kit will provide more strength, stability and a cleaner installed appearance for any Mustang that uses them.

Since you are increasing the flow out the rear of your Mustang, it’s a great idea to also increase the airflow that’s coming into your engine. Supporting mods like:

• cold air intake
• throttle body
• high flow filters
• Bama Custom Tunes

To maximize the sound and performance gains associated with your new exhaust, be sure to check out our full line of Cold Air Intake, Throttle Body and Tune packages available. 

You've probably come across a ton of information in your research of exhaust, so we'll try to simplify it for you now. These are the basic rules to keep in mind when buying exhaust parts:

• If you're buying shorty headers or have the factory manifold, you will need to buy a standard length mid-pipe
• If you're buying long tube headers, you will need to buy a shorty mid-pipe
• Cat-back and axle-back setups will work with either header/mid-pipe combination

The majority of the Mustang parts we sell can be used together. This means that you can use BBK parts with Magnaflow parts, and not have any problems with fitment. There is an exception to that rule, though.

Long tube headers can only be used with the same brand shorty mid-pipe. (E.g. SLP long tube headers can only be used with an SLP shorty mid-pipe.)

Other than the exception above, you can mix-and-match parts on your Mustang. When it comes down to it, however, it’s better to be safe than sorry. Stick with the same brand for all of your exhaust parts. If you buy BBK headers, then get a BBK midpipe and cat-back. By doing this, you can be 100% certain that all of your parts will fit together perfectly.

When piecing together a new exhaust setup, it is important to pay attention to the diameter of the piping as it will play an integral role in your Mustang's performance. When you are flowing more air into your Mustang's engine (whether it is an upgraded intake manifold or a supercharger/turbocharger setup) you will want to increase the exhaust piping size to help scavenge those exhaust gases more efficiently, making more power in the process.

However, it is important to only go as big as you need. If you go with the largest header size you can on an NA car, you may lose some power and back pressure as there is not as much of a need for the larger pipe size. Too large of an exhaust diameter can lower the amount of power an engine can make (in certain situations) because of low exhaust velocity. In basic terms, a water hose will move the same amount of water through a smaller hose diameter at a faster rate. On the other side, if the flow is the same but the pipe is larger, it will not have to flow as fast to move the same amount of water. The same analogy can be utilized towards exhaust. If the engine is not moving enough exhaust, increasing the diameter of the pipe can slow the velocity of the exhaust.

It is also crucial to pay attention to piping size when assembling a full exhaust setup as you may need an adapter to make some exhausts work together if they are different sized exhausts (i.e. a 3" mid-pipe connecting to a 2.5" over axle pipe).

Stock Mustang exhaust piping sizes are as follows:

• 1979-2004 (Foxbody, New Edge, & SN95): 2.25"
• 2005-2010 (S197) V6s: 2.25"
• 2005-2010 (S197): 2.5" with 3" tips
• 2011-2014 (S197) V6s: 2.5"
• 2011-2014 (S197) GTs: 2.5" or 3" with 3.5" tips
• 2015-2018 (S550): 2.25"

An IRS equipped vehicle will have the exhaust routed under the axles due to vertical travel of the rear end. Space is also a factor because an IRS rear-end is much more complex and bigger than a traditional live axle (straight axle) setup. IRS Mustangs include the 1999-2004 Cobra and the 2015-2018 Mustangs.

• 1979-1985 5.0L & 1979-2004 V6s feature a single exit Y-pipe design with the muffler attaching before the rear axle
• 1987-2004 GTs feature a dual exit H-pipe design with the mufflers attaching before the rear axle
• 2005-2010 V6s feature a single exit Y-pipe design with a muffler attached after the rear axle
• 2005-2014 GTs feature a dual exit H-pipe design leading into an axle-back set

Most states will require catalytic converters, so you should always check your state's regulations before purchasing a new exhaust kit for your Mustang. Just because an exhaust kit is listed as “street legal” it doesn't necessarily mean that it is emissions legal for your state.

Maybe you're not worried about keeping your Mustang street legal. Instead, you're looking to rattle your neighbors' windows with the loudest exhaust setup you can find. Making your Mustang louder is going to err on the side of not so legal more often than not. The loudest configuration would be a set of long tube headers, an off-road mid-pipe, and straight through mufflers.

MIL (Malfunction Indication Light) eliminators are used when an off-road mid-pipe (no catalytic converters) is installed. Your car’s computer is programmed to work with cats on the car. When you remove them, the check engine light will come on because of the readings that the car’s computer is receiving from the rear oxygen sensors. The MIL’s essentially trick the car’s computer into thinking that the cats are on the car and that the oxygen sensors are performing properly. MIL eliminators will not bypass a malfunctioning oxygen sensor. They will only shut off the "check engine" light when installed on properly functioning O2 sensors.

To prevent the light from coming on, 1996-2004 Mustangs will either require a set of MIL Eliminators or a tune with the rear O2 sensors shut off. MIL, which is short for Malfunction Indicator Light Eliminator, plugs in between the rear O2 sensor and the harness to block the codes generated by the rear O2 sensors. The MIL Eliminators will allow you to pass an OBD II inspection, but if you have visual or a sniffer, you will fail. If you have the rear O2s turned off in the tune, you will also fail as they will not read ready. If you have a 2005 or newer Mustang, you must have a tune to shut off the rear O2 sensors.

If you own a 2007 Mustang, we recommend you upgrade the exhaust hangers that are currently on your car. In the 2007 model year, Ford changed the design of their exhaust hangers to a lower quality hanger, and with the new design, we have run into issues with proper exhaust alignment. The new hangers are not a requirement, but we HIGHLY recommend them.

But where are they located? Mustang exhaust hanger locations are the same within a generation. So all Foxbody hangers will be in the same place, s197 hangers will be in the same place, but there is one exception. Single outlet exhausts. If you're converting a V6 to a V8 style exhaust, you'll need an additional hanger and you'll need to modify the rear bumper. Depending on the situation, a different mid-pipe might need to be utilized as well.

It depends on the exhaust part you are installing. Cat-back and axle-back kits never require tuning. If you are making changes to your headers or mid-pipe, it is more than likely that you will need a tune to not only calibrate the vehicle for the new parts, but to also maximize the performance you get from them. This is not the case for every application, but it is more common than not.

While stock exhaust works for supercharged applications, there are better aftermarket setups. In the best situation, long tube headers, an offroad mid pipe, and a cat-back would be the best setup for a supercharger. However, this can be heavily impacted by emissions and inspections.

Short tube headers are not the best, but prove to be a good supplement over stock exhaust manifolds. Another supplement is a quality set of high flow cats. Replacing these instead of the stock catalytic converters can increase airflow while still being emissions friendly.

Emissions testing is unique to each state. While some states do not participate, others go above and beyond to make sure that federal requirements are met. Most states that test do one of 3 tests:

Visual test - The visual test is simply what it says, it is a visual inspection to make sure that catalytic converters are being utilized. This is primarily accomplished by having mirrors that can be used to see underneath the vehicle.

Computer test - This test hs completed by plugging a computer to the OBDII port of the vehicle and reading the output that sensors are giving. Some states allow one set of sensors to read N/A or not ready, with the exception being rear O2 sensors. As a result, O2 sensors must be on and reading correctly in order to pass.

Sniffer test - A sniffer test uses a device that is placed near the tailpipes of the vehicle. It measures the quality of the exhaust being discharged and determines whether catalytic converters are in proper working order.

With those tests, it is generally pretty difficult to pass with rear O2 sensors on. Some states allow for rear O2 sensors to read N/A or not ready, while computer tests can be tricked by using MIL eliminators (on 1996-2004 models).

C.A.R.B. stands for California Air Resources Board and has a say in what you can and can't put on your Mustang if you live in one of the states that follow their regulations. Unfortunately, C.A.R.B. compliant states limit how you can modify your Mustang's exhaust, but below we've compiled of list of parts that are C.A.R.B. approved.

2015 (S550) Model Year - Because of where the catalytic converter is positioned, The 2015 GT cannot change headers and be C.A.R.B. legal. The EcoBoost cannot change the downpipe. Cust and clamp or resonator delete setups are the best bet for 2015 GTs and EcoBoosts that need to be C.A.R.B. compliant.  

Compliant Headers

• EcoBoost - None
• GT - None
• V6 - BBK Ceramic Tuned Length Shorty Headers

Compliant Midpipes

• EcoBoost - Flowmaster Scavenger Series Cut and Clamp Resonator Delete Y-Pipe
• GT - Heartthrob Cut and Clamp Resonator Delete H-Pipe

2010 - 2014 (S197) Model Years - Shorty headers and manifolds only. Long tube headers will not be C.A.R.B. legal. "High flow" or "off-road" cats or mid-pipes are not likely to be C.A.R.B. legal.

Compliant Headers

• GT - BBK Ceramic Tuned Length Shorty Headers & JBA Shorty Headers
• V6 - BBK Tuned Length Shorty Headers

Compliant Exhausts

• Catbacks and Axelbacks

Special Note: 2010 Mustangs

Compliant Headers

• GT - BBK Chrome Tuned Length Shorty Headers
• V6 - BBK Tuned Length Shorty Headers & JBA Shorty Headers

2005 - 2009 (S197) Model Years - Same as 2010-2014. Compliant parts are the same brand and style as the 2010.

1999 - 2004 Model Years - Same as 2010-2014. Compliant parts are as follows:

Compliant Headers

• GT - BBK Ceramic Tuned Length Shorty Headers & JBA Shorty Headers
• V6 - BBK Chrome Shorty Headers & JBA Shorty Headers

Compliant Exhausts

• Catbacks and Axelbacks

Remember to look for the C.A.R.B. EO number when considering exhaust options! If the part has a C.A.R.B. EO, it's C.A.R.B. approved.

H and X-pipes for the 1999-2004 Mustang will fit all the 4.6 motors including the Mach 1 and the Cobras. They will fit, however, for the Mach 1 the O2 sensors are in a different location than the Mustang GT location. Below is a picture a fellow enthusiast drew up with all the different color arrows of a Mach 1 Mustang labeling the location of the oxygen sensors, and the other is the picture of the regular GT H-pipe. As you can see the Mach 1 O2 sensors are located farther away than the GT locations, so the Mach 1 will need O2 extensions. 

Upgrading the intake allows your engine to suck in more air. The intake can be just the filter and the air tube (also known as the cold air intake), or it can also be the manifold itself. Either way, the stock intake cycle, from filter to manifold and including the throttle body, is choking up your engine. 

Replacing the intake system from the filter to the manifold will allow your engine to take in a considerably larger amount of air, which in turn will help your Mustang to make more power.

In the simplest of terms, power is made by mixing air and fuel, so once you have upgraded how much air your engine can take in and expel, you’ll want to upgrade how much fuel your engine can suck in. Going to a higher rate fuel injector will give your Mustang much more power when combined with the other previously mentioned modifications. 

When you don’t upgrade the fuel injectors, but you do upgrade the exhaust/intake cycle, your engine will starve for fuel in the high-mid range up to redline. There is no use in upgrading your engine to take in all of that extra air without being able to throw some extra fuel into the mix as well.

Going off of the previous section, your cylinder heads dictate how much fuel and air your Mustang can mix together to make power. By not upgrading them, you are limiting how much power you can make and where in the power range you can make it. Cylinder heads are typically costly in part cost and in labor to get done, which is why they are not a super common modification. However, they are one that can make a big difference.

Camshafts dictate the amount of air that enter and exit and engine, and when air can exit in terms of the overall timing. Are you starting to see a theme here? Swapping out the stock camshaft for an aftermarket one will allow you to improve the ignition/combustion cycle of the engine, feeding more air into the engine and allowing it to get out easier. 

Outside of the supporting mods that will help your engine to not only run more efficiently, but make more power, there are also a selection of other upgrades you can make that will just improve reliability or functionality.  There are quite a few exhaust accessories available for late model Mustangs that can include:

• O2 Sensors (extensions and wires)
• Over-axle pipes (the cat-back piping without the muffler/axle-back)
• Exhaust tips (add-ons for the muffler, dress up part)
• Exhaust heat wrapping (typically used on headers to keep engine bay temps down)
• Catalytic converter delete pipes (removes the cats from the system)
• High flow catalytic converters (adds cats to the exhaust system)
• MIL Eliminator (removes the check engine light after removing the cats)
• Exhaust hangers (replaces worn/rusted hangers and holds the exhaust in place)
• Gaskets (to go in between the headers and the engine, making a tight seal)
• Exhaust cutout systems (opens up the exhaust system before the mufflers, provides a loud tone)

Picking out different exhaust accessories is going to come down to your build and what it needs (and sometimes what you want).

Most people try to cool down their engine by upgrading their radiators. Makes sense. However, there are other ways to augment cooling upgrades and take advantage of the heat.

• Exhaust wrap insulates the exhaust pipes to keep heat in inside of dispersing into the engine bay
• Soaking the wrap in water and then installing it allows the water to evaporate and tighten the wrap as it dries
• Hotter exhaust gases allow for better scavenging for more clean air in the combustion chamber
• Cooler intake chargers means denser air and more potential power

Exhaust heat wrap is a flexible material cut into strips used to insulate your exhaust system and trap heat inside the pipes. The heat wrap is made from materials like fiberglass or volcanic rock processed to withstand the extreme temperatures of your Mustang’s exhaust. To get the best performance out of your exhaust wrap, you should soak the wrap in water, then tightly wrap it around your exhaust, overlapping each pass slightly. By getting the wrap wet, you will be able to stretch it more as you wrap it. As the water evaporates out of the wrap, it will contract and give you a tighter wrap. You can also paint the wrap with high temperature paint to make it look better, but this is not necessary

Wrapping your exhaust will help increase the performance of your Mustang in several ways. The first is keeping your exhaust gasses hot. Heat always seems to be the enemy for the performance enthusiast, but a hotter exhaust allows for better cylinder scavenging. This means the hotter exhaust will move from the cylinder faster, allowing more clean air to come into your engine. This probably will not produce a difference you can feel, but a better flowing exhaust is always something you want to have. The second way exhaust wrap helps your Mustang is by reducing ambient heat. The exhaust generates a massive amount of heat, which in turn will saturate the engine bay with ambient heat. This heat will make its way into your air intake, intake manifold, fuel rails, and many other parts of your engine. By insulating the exhaust, you are able to reduce the ambient heat. This reduction in ambient heat will lower your fuel temperature and air intake temperature, resulting in a slight increase in power and efficiency. The cooler you can get your incoming air/fuel mixture, the denser it will be. The denser the mixture, the more you can fit into your cylinder which results in more power.

Wrapping your exhaust is not a difficult task, but it can be time consuming to do properly. If you are installing a new set of long tube or shorty headers, wrapping your exhaust would be a great way to squeeze a little more power out of your new exhaust system. If you already have a set of long tube or shorty headers installed, the time and energy spent removing your exhaust and wrapping it would probably not be worth the slight gains you would see. You should also avoid wrapping your exhaust if you live in a very damp environment, or you drive the car in the winter where road salt is used. If you live in a damp climate, the wrap can trap moisture against your exhaust which can lead to premature failure. The same holds true for road salt, or other corrosive elements used in your area.

Catalytic converters have been equipped on all new cars in the United States since the 1975 model year to comply with U.S. Environmental Protection Agency regulations on automobile exhaust emissions. Their purpose is to convert the toxic byproducts of the internal combustion engine, exhaust gases, into less toxic substances by way of a catalyzed chemical reaction for release back into the atmosphere. Catalytic converters or “cats” look like small mufflers and are normally located directly after the exhaust manifolds (a.k.a. headers).

After combustion, the main remaining products are carbon dioxide, nitrogen, water (vapor), carbon monoxide, hydrocarbon compounds, and nitrogen oxide(s). The first 3 – nitrogen, carbon dioxide and water vapor – are harmless (well, we are aware of the potential environmental effects of CO2). It is the last 3 products that pose health risks. Thus, it is the job of the catalytic converts to take carbon monoxide, hydrocarbon compounds, and nitrogen oxide in, and turn them into something else. After passing through a properly functioning catalytic converter, carbon monoxide, and hydrocarbons will be turned into carbon dioxide, and the nitrogen oxides (NO and NO2) will be ripped of their nitrogen atoms and released as nitrogen gas. So, if we were to analyze what is coming out of the tailpipes, all we should mainly see is carbon dioxide, water vapor, and nitrogen gas.

Just to clarify (and without going too deep into the chemistry of it), don’t think that any elements mysteriously disappear inside the catalytic converter. Rather, the elements are just rearranged (by interacting with specific chemicals contained in the converter) into less damaging by-products (carbon monoxide becomes carbon dioxide by attaching another oxygen atom)

All new cars come with catalytic converters. The cats are located on the mid-pipe, and depending on the year of your Mustang you could have up to 4 cats. The more cats you have, the more restricted your exhaust flow will be. Aftermarket companies offer high flow catalytic converters for people who wish to increase their exhaust flow, while keeping their exhaust note more tame, and reducing the raw fuel smell typical of an off-road system. Most aftermarket cats will pass emissions testing. In California, you will want to make sure you have a CARB approved converter.

In the older days when converters were newer to the market, they did indeed rob cars of a good chunk of horsepower. However, in more modern times, they have become more efficient and hardly rob power in smaller HP circumstances (<500). The gains are minimal from removing and not truly needed unless you’re building a full out drag or race car. Much like a cold air intake, you might notice a bump in power, but don't expect a game changer.

• Catalytic converters change harmful engine emissions into less harmful emissions before shooting them out the tailpipe
• With older muscle cars, it is common to remove or replace the stock catalytic converters to increase horsepower
• High-flow catalytic converters reduce harmful emissions while decreasing resistance and increasing lost horsepower

Factory catalytic converters have a very densely packed catalyst substrate to ensure that they are 50 state legal and that non-enthusiast drivers aren’t subjected to increased exhaust sounds and smells. The image above shows the inside of a stock cat. High flow cats dramatically increase the exhaust flow since their substrate is not as dense as the factory converter. Below is a shot inside a high flow cat.