How to Modify Your V6 Mustang's Exhaust - Dual Conversion & More!

Are you going for a more enjoyable sound alone, or for sound and a jump in performance? This is a preliminary choice you must make before diving into modding pieces of your Mustang's exhaust. Each part of this system can usually be replaced individually, and each part of the exhaust system also holds unique sound and performance characteristics. You can also replace everything in favor of a dual exit conversion.

• Mufflers are engineered around sound; choose a design you like
• A muffler alone can also alter your Mustang’s sound without redoing the entire exhaust
• Different style mid-pipes have their own performance gains
• H-pipes provide a classic muscle car sound while x-pipes are throatier
• Street Mustang or track star? Real catalytic converters or straight throughs?
• Headers provide the biggest horsepower gains out of any exhaust component
• Shorty headers can be tuned length to maximize flow
• Short headers give you less of a power boost over long tubes, but can accommodate a turbo upgrade and are easier to install
• Long tubes give a great boost in horsepower, torque, and sound
• Dual exhaust conversion gives you even more flow and more options for sound overall
• Cat-backs further personalize your Mustang’s sound

Let's consider just how restrictive the V6 system is. Gases leave the engine through the two exhaust manifolds, but get slowed down after the catalytic converters. The gases are then forced through a single pipe to pass through the muffler and out of the tailpipe. Looking at it like this makes it easy to see why the V6 setup restricts air flow and limits power.

Headers attach to the exhaust ports on the cylinder heads and connect to the mid pipe section of the exhaust.  If you are a bit more concerned with horsepower gains then understand the greatest gains will come from the headers. The x-pipe and mufflers are only good for 5-10 HP at most. A full exhaust system on a naturally aspirated Mustang will yield around 15-20 rear wheel HP while on a forced induction application those number would be around 20 to 30 rear wheel HP.

Shorty headers are what your Mustang came with when it left the factory, and an aftermarket set is typically easier to install than long tube headers. However, a set of 1-5/8” long tubes will get you the most power for your money. Keep in mind, long tube headers cannot be used on a turbocharged Mustang. Both shorty and long tube V6 Mustang headers are available with ceramic coating that helps reduce temperatures under the hood, keeping your engine bay cooler by retaining less heat and thus allowing your motor to produce more power. Long tubes also require relocation of the O2 sensors and possibly a re-tune of the computer to compensate for the change.

Long tubes will also give you more consistent performance throughout the power curve, whereas shorty headers do the most for you in the mid-range rpms. For anything less than a heavily modified V6, there won’t be much difference in power so keep your selection based on the long-term goals for the car (don’t forget, if you plan to go turbo you can only reuse shorty headers!) and the finish material the headers are coated with.

Your V6 Mustang’s mid-pipe connects the headers to the cat-back portion of the exhaust. This single tubed exhaust then extends over the rear axle and out the back of the car. The factory y-pipe is designed for a single exhaust setup. The pipe only utilizes a single exit point. An example of this can be seen on the 05-09 V6. A GT X or H-pipe utilizes two different exit points. This allows for dual exhaust. 

The style of mid-pipe you need for your Mustang will depend on which headers you choose. If you are using the factory headers or maintain the shorty header design, then you need a y-pipe unless you choose to go with a dual exhaust conversion. The dual exhaust conversion mid-pipe uses your factory catalytic converters and allows you to bolt up any GT style exhaust. Aside from the GT mid-pipe, you'll also need the additional muffler, and the second set of hangers (2) for the added piping assuming, of course, you don't decide to go with a GT cat-back.

If you want to keep your factory Y-pipe, there are kits for that (check out the video below). Keep in mind you won't have the same sound as a V6 with the GT style mid-pipe.

If you are one of those people who are not looking for maximum performance, but would rather your Mustang give a mean snarl when you stab the pedal, you might want to save a few bucks and replace the single exhaust setup with another, better sounding and performing y-pipe. That way you save a few bucks on the parts and install cost but still achieve a throatier, more muscular sound. Keep in mind when ordering mid-pipes “off-road” refers to the elimination of catalytic converters and should only be used at the track.

The cat-back portion of your V6 Mustang’s exhaust connects to the end of the mid-pipe and exits out the rear of the car. This is the piece that contains the mufflers. Choosing the appropriate cat-back will depend on which mid-pipe you are running. If you are using the standard or aftermarket y-pipe, then you will still need a single exhaust cat-back system or a dual exhaust that splits after the mid-pipe. If you choose to go with an x-pipe, h-pipe, or dual exhaust conversion kit then you can choose from the GT selection of cat-backs.

There are mainly two different styles of mufflers--chambered mufflers and straight-through mufflers. Chambered mufflers force the exhaust gases to go through a series of chambers inside of the mufflers before exiting the rear of the car. Typically, the more chambers in the muffler, the quieter the exhaust note will be. Straight-through Mustang mufflers route the exhaust gases straight through the center of the muffler causing the exhaust note to be much louder. So decide which sound you want for your Mustang and go from there.

Then you have a choice of catalytic converters or straight-through pipes. Many people choose the cats for street driven Mustangs. This way, you can still pass emissions tests and also be street legal.

Many look to remove the cats to improve exhaust flow, but it also results in a byproduct of improved sound quality. The exhaust note will be muffled inadvertently when catalytic converters are present due to their nature. Removal of the cats will result in a change but not as much as you would think. The sound level will improve slightly so if you’re looking to make big changes you may want to look elsewhere. Larger pipes and proper mufflers are the real way to improve sound quality.

Most manufactures make the individual components bolt directly to the factory system. All of the exhaust components are fairly easy to install. While it would be good to have a lift, some people have put them on in their garage.

There are certain ways to allow GT exhaust to be utilized on a V6 Mustang. The primary difference is pipe diameter and the dual exhaust on a GT vs the single exhaust on a V6. There are a couple of options V6 owners can look at here. Both options require either cutting or slight modification of the rear bumper and a set of exhaust hangers for the added side of the exhaust.

1) Get a mid-pipe (X or H) and utilize a GT cat-back.
2) A mid-pipe, GT over axle pipes, and GT axle-backs. These changes will allow for proper fitment of a GT exhaust onto a V6 Mustang.

Using a dual exhaust adapter kit requires cutting your y-pipe right after the catalytic converters and welding the adapter into place. The adapter acts as a splitter, allowing you to bolt any GT cat-back for your year Mustang right up to it, giving you the look of a true dual exhaust.

The downside to this is using this kit does not actually give you a true dual exhaust. It gives you the look and sound of a GT exhaust, but you will only see minor performance gains. The 1994-1998 conversion kit is slightly different than the 1999-2004 kit, so be sure to select the kit that’s built for your car.

One option to converting to dual exhaust is to use a V6 specific mid-pipe. Designed to eliminate the single pipe design of the factory y-pipe, these bolt right up to the factory manifolds and give you a true dual exhaust. With this option, you can use any GT cat-back for your year Mustang. There is a sound difference between the two with the h-pipe having a more classic Mustang sound.

Because this conversion gives you a true dual exhaust, you will have noticeable performance gains. Your Mustang will be able to support more horsepower, though how much of a horsepower gain you will see depends on whether you keep your cats or go for an off-road set-up. Between buying adapter kits or a mid-pipe, the mid-pipe is the easiest option. There is no precision cutting or welding, and it can be done by anyone with basic tools and knowledge.

If you are of the DIY mindset, then your cost of installation is going to be the price of the kit plus 2-4 hours of your afternoon (pending you have all of the tools you need). However, if you’re looking to leave it to a professional, you’re looking at the price of the kit and an install cost that can range from as low as $150-$450 depending upon the shop. Shop costs and labor rates vary from shop to shop, so it may be a good idea to call the shop you are thinking of using and seeing what they charge.

Another potential mod is quad exhaust like the GT500. Like most exhaust work, the task can appear simple. However, it can be come a more daunting task than it appears. Not only does a quad conversion require cutting the stock exhaust in most cases, it can also require modification of the bumper to fit the multiple tailpipes themselves. At a mininum, you would need a GT500 rear valance, quad axleback exhausts, and a new midpipe to resize the exhaust diameter of the axlebacks (if neccessary).

There are two options that one can choose from. First, cut the current valence in order to accommodate the second pipe. This is pretty straight forward and most kits come with a template. However, one has to be careful in order not to cut in an improper way. Second, purchase a GT rear bumper and install that onto the rear end. That would give the second cut out that matches on both sides and allows for the proper fitment of the second pipe as well.

While a tune certainly helps the drivability, it is not necessary unless your dual exhaust is manipulating your catalytic converters or converting to long tube headers. If for the catalytic converters, a simple handheld tuner can turn off the rear O2 sensors to turn off the check engine light.

If you have a stock V6, there are a few things we recommend to keep you from losing low-end torque and having a sluggish car. First, get a mid-pipe with catalytic converters. True, you won't see as much of a horsepower gain but, using a mid-pipe with cats creates enough backpressure to keep your low-end torque drivable. Second, use a chambered muffler (such as Magnaflow, Steeda, Pypes), instead of a straight-through muffler.

Note: If you really want to use an off-road mid-pipe on a stock car switch to steeper gears (4.10s or higher). This will get you into your power band faster, and the low-end torque difference will be less noticeable. Although if your V6 has forced induction or nitrous, it’s okay to use a straight through muffler and an off-road mid-pipe.

If you are primarily interested in a louder sound then your journey is just starting. A good place to start is by searching different exhaust combos and listening to exhaust sound clips provided on each page. You can also try to find other Mustangs at car shows and Mustang club meets. This can take a bit of time to research properly. Some systems are very loud and some are milder, yet may have a noticeable highway drone.

Many V6 Mustang enthusiasts are concerned with creating said drone. If this drone is a concern, make sure to avoid mid-pipes and cat-backs with straight-through mufflers or resonators. Resonators will “resonate” the noise and can cause more of a drone. Another source of exhaust drone or popping can be caused by piping that is too large in diameter. Ideally, most V6 Mustangs should utilize between 2-2.5 inch mandrel bent piping. Larger piping (2.5 inch) can accommodate more horsepower but too large a diameter can actually hurt performance and power numbers. Again, it’s all about your current and future plans for the car.