Upgrading Your Mustang's Exhaust

Posted 8/31/2018 by Tyler Rodriquez

One of the first mods anyone does to their Mustang is add a new exhaust. Let LMR walk you through exactly how to go about upgrading your exhaust system.

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If you’re thinking about changing your Mustang’s exhaust system, here’s an important fact to know — there are three main components to the exhaust system and all Mustangs, regardless of when they were built or the generation, are set up the same.

We understand that buying parts for a new Mustang exhaust system is confusing. You have many brands from which you can choose, and you need to understand which of these parts will work together so that your exhaust system sounds great but is still efficient.

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The Basics

First, let’s look at a basic aftermarket exhaust system.

When your car comes off the factory floor, the exhaust system on the vehicle is designed with one main goal in mind — to muffle as much sound as possible. So it restricts the engine’ s flow of exhaust gases which creates back pressure. Almost every engine requires a bit of back pressure to work properly. But there is one drawback to back pressure — it takes away power from the engine. That’s because the engine has to use some of its power to send exhaust gases out of the tailpipe instead of that power being used for the vehicle.

You can recover some of that power if you replace the factory exhaust system with component parts that are less restrictive yet still meet all legal vehicle requirements.

So what are the parts of an exhaust system?

1. Headers or Exhaust Manifolds

First, you have the headers or exhaust manifolds. These are the first components of an exhaust system that deal with the gases that come from your engine. These headers or manifolds are attached to the cylinder heads and take away exhaust gases from the engine’ s combustion chambers.

Aftermarket manifolds are mandrel-bent. This reduces exhaust restrictions so that the exhaust gas can move more freely from the engine. This limits back pressure and its ability to rob power from the engine and creates enough exhaust flow velocity to generate energy impulses that take spent gases away to the engine.

2. Downpipe

Downpipes, or head pipes, link the headers to the mufflers. The catalytic converter often interrupts the downpipe, depending upon how it is built.

3. Catalytic Converter

If your car was manufactured after 1975, it probably came outfitted with a catalytic converter, sometimes called a "cat." The job of the catalytic converter is to reduce the emissions released by your vehicle into the air.

If you travel on public roads, you’ll need a catalytic converter. Federal and state regulations require one.

The exhaust gases from the engine flow through ceramic honeycombs, which are coated with precious metals. When the gases contact the coating, it initiates a chemical reaction. This converts emissions to carbon dioxide, oxygen, nitrogen and water.

4. Muffler

Almost everybody knows what a car muffler does. It reduces noise. But how it reduces noise depends upon the type of muffler being used. It normally relies on some combination of chambers baffles, perforated tubes and possibly material that acts to deaden sound. An aftermarket muffler can give you what you’re looking for in a performance exhaust tone but reduces the back pressure that steals power.

5. Crossover Pipes

Designed for a dual exhaust system, crossover pipes balance exhaust flow. Normally they are installed near the headers and act to reduce and even exhaust flow from both banks of engine cylinders. They give exhaust pulses a way to travel between the sides of the dual exhaust system. By preventing exhaust buildup on either side of the system, it reduces back pressure. The most common types of these pipes are X-pipes in H-pipes, so named because they look like the letters X or H.

6. Tailpipe

The last component. It goes from the muffler to the back or side of your car. Aftermarket manufacturers like to give tailpipes a little bit of flash so often include a chrome exhaust tip or one that is polished. You can also buy exhaust tips in your choice of finishes or shapes.

Upgrading Your Mustang

So as you can see, the main purpose in putting an aftermarket exhaust system on your Mustang is to give you more power for your drive.

What Are the Components of a Mustang's Exhaust System?

Now that we have a good view of how exhaust systems work for all cars, let’s look at the components for a Mustang exhaust.

1. Exhaust Manifolds Versus Headers

A Mustang engine's exhaust ports connect to the exhaust manifold. The exhaust gases are funneled towards the mid-pipe. Manifolds are sometimes called headers. Although they carry out a similar function, these two are not the same. Exhaust manifolds are headers originally put on by the factory. All the holes from the manifolds connect to the same chamber.

The tubes of an aftermarket manifold are designed to connect the exhaust ports to the pipe. If you use “shorty headers,” they attach to the factory manifold. “Long tube headers” are designed for use in racing. You also have equal length headers, which are either a shorty or a long tube, and they improve exhaust flow. What makes this modification so popular are the curves. The curves allow the exhaust gases to easily enter the pipe instead of slamming them through, which reduces power.

2. Headers — Full-Length, Long Tubes and Shorties

Stock manifolds and shorties are the same sizes. They will work with either aftermarket mid-pipes or stock mid-pipes. Shorties are excellent for Mustangs that are turbo-charged. They provide greater torque and more horsepower in a stock manifold but do not give you the equivalent power of a long tube.

Long tube headers and stock mid-pipes don’t work in place together. Long tube headers are too long to connect to the stock mid-pipe. If you’re going to use a long tube header, you will need a shorty mid-pipe to create the proper exhaust length. The expression "full-length header" is another name for a long tube header. Long tubes provide more torque and improved horsepower, but they will not work with motors that are turbo-charged.

3. Mid-Pipes

Every Mustang exhaust has a mid-pipe. It’s where the gases go after leaving the manifold. V6 mid-pipes differ from GT mid-pipes.

  • GT Mustangs have a stock H-pipe.
  • V6 Mustangs have a stock Y-pipe.
  • You can also purchase aftermarket X-pipes.

4. Catalytic Converter

Every stock mid-pipe comes with a cat – a catalytic converter. As mentioned above cats, make exhaust emissions friendlier for the environment. If you use your vehicle for racing or off-roading, you won’t need a catalytic converter, and the aftermarket mid-pipes you can purchase are called “off-road H- or X-pipes.” Remember mid-pipes designed to be used off-road are not okay for street use, and probably won’t pass your state’ s emissions inspection.

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What’s the Difference Between an Axle-Back and a Cat-Back Exhaust System?

A cat-back is placed behind a catalytic converter. It contains the muffler and the tailpipe.

An axle-back is also the final component of an exhaust system. But instead of bolting on behind the catalytic converter like a cat-back, an axle-back bolts behind the muffler.

1. Overview of Cat-Back Exhaust

  • Runs from the catalytic converter to the rear of the car
  • Is quieter than a long tube header, but definitely louder than an axle-back
  • Gives you a full, deep exhaust note without a tune

2. Overview of Axle-Back Exhaust

  • Travels from the rear axle to the rear of the car
  • Offers a sizable improvement over a stock exhaust system but is still softer than headers or cat-backs
  • Provides you with a variety of sounds based on the system — some will wake your neighbors, and others have a low-key rumble

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Can Mustang Components Be Used Together?

With so many different Mustang components out there, you might be wondering which parts can be used together. Here's what you need to know:

  • If you’re using shorty headers or using the manifold from the factory, you need a pipe of standard length.
  • Long tube headers will only work with a shorty mid-pipe made by the same company.
  • If you want a cat-back or axle-back set up, they will work with many headers and mid-pipes.
  • While it is possible to pick components from different manufacturers for your Mustang's exhaust system, the best idea is probably to use the same manufacturer for the different parts. It's the one way to be sure that components fit each other.

When you’re building an exhaust system that is new for your vehicle, keep an eye on the piping sizes. Size plays a very important role in how your Mustang performs. If you’ve upgraded an intake manifold or installed a new supercharger or turbocharger kit, you have increased the air flow into the engine. In that case, you’ll need to expand the size of the exhaust piping to better deal with exhaust gases, thus creating more power.

But a word of caution — don't make it any bigger than you need to make it. If you use a large header size, it will cost you back pressure and thus power as well since you won't actually need a bigger size. A too large exhaust diameter will decrease engine power because the exhaust velocity is lower.

Think of it like this — if your kitchen sink has a small pipe, it will send water through at an increased speed. But if your kitchen sink pipe is too big, the flow will move more slowly to run a similar volume of water. So if you make the pipe bigger but the engine is still pushing the right amount of exhaust, you slow the exhaust velocity.

Why Is Stock Exhaust Routed Underneath a Mustang's Body?

A vehicle equipped with IRS (Independent Rear Suspension) features the exhaust placed beneath the axles. This is because of the way the rear of the car deals with vertical travel. The back of a car with IRS is larger and has a more complex structure than a normal straight axle set-up, so space becomes a factor. The 1999-2004 Cobra and the 2015-to 2018 Mustangs are IRS vehicles. These are the layouts for other Mustangs:

  • 1985-1997 5.0 liter and 1979-2004 V6s have a Y-pipe with one exit, and the muffler is attached in front of the rear axle.
  • 1987-2004 GTs have an H-pipe with dual exits, and the mufflers are again attached in front of the rear axle.
  • 2005-2010 V6s use Y-pipe with one exit with the muffler behind the rear axle.
  • 2005-2014 GTs have an H-pipe with two exhausts that connect to an axle-back.

Street Legal Information

Before you purchase an exhaust system for your car, check your state regulations on catalytic converters. There can be differences from state to state. Just because an exhaust system kit says it can be used on the street in your state doesn’t mean that it actually will be legal in your state. Do your research.

If remaining street legal is not your primary concern and you want to wake up the neighborhood with the noisest exhaust system available, the configuration you’re looking for consists of using long tube headers, a mid-pipe that's "off-road" and a muffler that's straight-through.

When you want to use your Mustang in an off-road situation, and you add upgrades that will help you find the power you want, you’re going to confuse the car’s computer. That’s because the computer is designed to work with the catalytic converter. Once you take off the cat, the check engine light fires up. You will need a Malfunction Indication Light (MIL) eliminator.

A MIL basically tricks the computer in your car by making it believe you still have a catalytic converter and that its sensors for oxygen work as they should. A MIL won’t bypass an oxygen sensor that isn’t working. It only turns off the check engine light when you have oxygen sensors that are working properly.

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What About an Emissions Test With No Catalytic Converter?

Each state has its own emissions testing program. Some states don’t do any testing while others are very rigorous to maintain federal requirements. The states that do test perform one of the three following tests:

  • Visual Test: A visual inspection to check the catalytic converters. Inspectors will have mirrors that they will use to inspect under the vehicle.
  • Computer Test: A computer is plugged into the OBD-II port and reads the output from the sensors. The O2 sensors need to be operating and working correctly to pass the inspection. Computer tests can be fooled by using MIL eliminators on models between the years of 1996 and 2004.
  • Sniffer Test: A small device is placed near the vehicle's tailpipe. You will occasionally see these devices placed on the roadside in your area as a way for the state to check and see how many people are driving cars with the correct emissions standards. The device measures the exhaust that is being discharged to determine if the catalytic converters are working properly.

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Do I Need a Tune?

That depends. Some exhaust systems, like an axle-back or a cat-back, never require a tune. However, if you’re changing your mid-pipe or exhaust manifold/header, you will probably require a tune to calibrate your vehicle for these new parts and to make sure you are getting the maximum performance from them.

Upgrading Your Mustang

What Exhaust Systems Can I Get From LMR?

LMR can provide you with all the best components that you will need if you want to upgrade your exhaust system for either a more robust exhaust system noise or an improved performance. You’ll find the exhaust systems broken down by year, model and brand, which will make it very easy for you to find what you are looking for, regardless of whether you are mixing and matching components or using all the same brand.

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LMR Can Help You Find the Perfect Exhaust System Upgrade for Your Mustang

Since our founding in 1999, our goal has been to supply Mustang owners with the right parts at the right time. Everyone who works at LMR loves working on Mustangs, and we understand the passion you feel for this incredible car. The knowledge and experience we have built over the years working on late-model and more modern Mustangs mean that when you come to LMR, you will receive service that is second-to-none in our industry.

We know that the best way to continue growing our business is to treat people with courtesy and respect and do our very best to share the knowledge and experience we have gathered over the years so that our customers are happy with the parts and products they buy.

Although we are mainly known for restoration products, you can find first-rate Mustang performance and styling products as well. When you want to upgrade your car’s exhaust system to improve performance, and maybe make a bit more of that incredible Mustang sound, you will find everything you need at LMR.

You can call us at 1-866-507-3786 or leave us your details on our contact page, and one of our talented and experienced staff members will get back in touch as soon as possible.