Understanding Mustang Exhaust Systems
Written By: Andrew Cilio

There are three main components to the exhaust system, and all Mustangs have the same set-up, regardless of generation. We'll break down each variation of the systems, so you'll have a better idea what you'll want for your Mustang.

Typical Mustang Exhaust Overview

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.

Whats The Difference? Exhaust Manifolds vs. Headers

Exhaust manifolds are 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.

Shorties, Long Tubes, and Full Length Headers

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.

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.

Mustang Mid-Pipes

All Mustang exhausts have a mid-pipe. This 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

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 province's emissions laws, may not pass inspection.

Almost every mid-pipe our sponsors carry are standard length. They will work with stock exhaust set ups as well as aftermarket headers and catbacks. They should 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.

Mustang Cat-back Exhausts

The cat-back 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.

You may have seen the term “axleback” mentioned in your research about exhaust systems. Axleback systems are still the last piece of the exhaust system. They differ from a catback because they bolt up behind the mufflers.

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

Catback Exhausts

• 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 now as loud as long tube headers
• Offer deep, full exhaust notes without requiring a tune

Axle-Back Exhausts

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 load as doing a cat-back or headers
Different systems offer different exhaust notes, from more low-key rumble to waking your neighbors loud

What Mustang Exhaust Components Work Together?

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
• Catback and axleback setups will work with either header/mid-pipe combination

So, What Exhaust Brands Will Work Together?

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 catback. By doing this, you can be 100% certain that all of your parts will fit together perfectly.

Piping Size and Performance

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.

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).

Will my Mustang's Exhaust be Street Legal?

Most provinces will require catalytic converters, so you should always check your province'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.

Do I Need MIL Eliminators?

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.

Do I Need to Purchase Exhaust Hangers?

If you own a 2007 Mustang, it is recommend that 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 installers have run into issues with proper exhaust alignment. The new hangers are not a requirement, but we HIGHLY recommend them.

Do I Need a Tune With a New Aftermarket Exhaust?

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.

* Speak with one of our sponsors for the best exhaust system for your application.