What’s the Best Exhaust for Your Mustang?

One of the most common questions on the forums is: “What is the best/loudest/most powerful exhaust for mustangs?” Most people who buy late-model Mustangs usually go for one of three initial upgrades: cold air intake, ECU tune, or cat back exhaust. Here’s what I’ve learned after a bit of research.

What’s the Best Exhaust for Your Mustang? The best exhaust for your Mustang is the one that provides the best volume, tone, performance, weight, and looks within your budget. Finding the best combination of these factors is one of the most enjoyable experiences of modifying a Mustang.

Read on to learn about the different components of the Mustang exhaust system so you can find the best sounding and performing exhaust system for your needs.

 

Which Exhaust Kit Makes the Most Power?

Changing your mufflers or “cat-back” set up doesn’t make a meaningful difference in power output. You need to go a little farther in your customizations before you see a real improvement in horsepower. Let me explain why.

Modern exhaust systems don’t provide a lot of restriction to the flow of exhaust from the engine. Since your engine is essentially an air pump and needs to push the exhaust gases out before it can suck in more fresh air, making it easier for your engine will technically free up horsepower. However given the size of our exhaust systems, it is very difficult for the engine to do so already.

It is technically possible to scavenge some extra power by providing a smoother exhaust system that reduces turbulence of exhaust gases on their way out of the tailpipe, but it simply won’t be meaningful. There are some sites on the Internet claiming that changing the over axle pipes and mufflers will produce 15 or 20 more horsepower, but this is nonsense. I believe the number is closer to five, but a change of that amount is almost impossible to measure.

Believe it or not, I’ve actually heard of some cheap axle-back systems that will cost you a few hp!

It is certainly possible to modify your exhaust system in two ways that would increase performance.

First, install an exhaust system that does not include catalytic converters. The cats in our cars certainly do prevent exhaust from exiting freely. Many people choose to remove these. If your state does not smog or otherwise test the emissions of your car, you can gain 20 or 30 extra horsepower.

Second, anything you do to remove weight from your car including removing exhaust components will help your car to get down the road faster. Lots of drag cars have simple exhaust systems that do not include mufflers for this exact purpose. Your ears may bleed, but your car will go faster! If this is in the budget, try looking for an exhaust system with light-weight materials like stainless steel. They’ll be around 30 pounds less than the factory system.

Don’t worry about finding power from changing your exhaust pipes (except your catalytic converter). You’re not going to find much power. Just focus on looks and sound, because they don’t call the accelerator the “loud pedal” for nothing.

 

What’s the Loudest Mustang Exhaust?

Now we’re talking! Enhancing the volume of your Mustang is never a bad thing. The stock exhaust system is disappointing, to say the least in the volume department. Almost any one of the kids that you choose will be an enhancement in this area either in terms of sheer volume or tone.

For the record, as I mentioned above, the very loudest exhaust system you can get is a set of straight pipes. That is, pipes straight back from the engine. Straight pipes are not muffled in any way and are almost certainly going to be too loud for you, your passengers, your neighbors and any living thing with ears.

Keep in mind, cops love an excuse to pull over loud mustangs, even if they aren’t speeding. Don’t give them a reason to write you a noise violation. You won’t be happy

A better option would be some very low restriction mufflers. A popular option for these includes the Roush axle-back kit. They have a significantly meatier tone than the stock units, are lighter, and the volume is more than sufficient to turn heads.

A word of caution with these: they were designed with such low restriction that removal of the cats is not recommended. A friend of mine has these with removed catalytic converters and his wife now says that he has ruined his car and refuses to ride in it (cough, Connor Burdge, cough). You’ve been warned.

Word on the street also has the Borla ATAK mufflers as being a bit on the noisy side, as well. I’ve seen more than a few posts on the groups of people wanting to trade theirs due to the excess noise.

 

Avoiding Exhaust System Drone

While wide open throttle volume is certainly a selling point for an exhaust system, keep in mind that if you are driving your car on the street, most of the driving will be done at partial throttle. Perhaps you are driving on the way to work, or planning to make a phone call in the car. You always want to be mindful of buying an exhaust system that produces drone.

Drone is hard to explain. Cheap exhaust systems usually do this and you may have heard it for yourself without knowing how to describe it. It happens when the car is moving at a steady pace with an even accelerator and the noise is overwhelming. It usually happens on the highway. Kind of like a bad Honda Civic with a fart can muffler.

Drone is like a crazy girlfriend. Having a bit of drone may be okay for the first month or two, maybe even enjoyable for a bit, but you’ll get tired of it quickly. You can never get away from it. It’ll follow you everywhere.

You want to avoid this at all cost. If you find a set of mufflers that you like, give it a quick google and see if you can find someone doing pulls with it. Chances are, they will comment about any sort of drone because it’s just too hard to ignore.

 

Do You Need to Upgrade the Whole System?

Some of the larger aftermarket parts manufacturers, especially those that specialize in exhaust parts, will be happy to sell you a complete kit including headers, X pipe, over axle pipes and mufflers. Some of these kits are absolutely beautiful works of art, especially when it comes to the polished stainless steel versions, like the kit that we installed for a customer on his 03 Mustang Cobra (above).

If you want to reclaim the most power possible from the exhaust system, changing out the factory headers to long tubes will get you a few extra horses. Changing the stock H pipe to a large diameter X pipe will also get you a few. Removing the catalytic converters will get you a few more. All in all, you could see some significant, measurable performance gains if you add them all up.

However, this gets tricky when you factor in the total cost of doing everything. “Combo” kits of headers and matching X pipe will run you between $1500 to $1800 for a high-quality kit. When it comes to horsepower per dollar, if you’re able to reclaim say 30 wheel hp, you’re looking at $50/hp. That’s not terrible, but compared to a power adder kit of $35/hp, it can get a bit pricey.

 

Can You Mix and Match Parts Exhaust Parts Easily?

There are some aftermarket companies that provide exhaust systems with unique connection points. For example, Borla pieces do not connect to factory pieces, unless explicitly mentioned or custom fit. Borla sells their pipes as complete kits. That means that while you can buy the parts separately, you can’t mix and match. Borla headers will only work with Borla X pipes that only work with Borla over axle pipes that only connect to Borla mufflers.

This can lead to issues if you’re using different components or take off parts, but it doesn’t apply to all manufacturers. Kooks, for example, provides an X-pipe that steps down from a 3″ diameter to a 2.75″ diameter to connect to the factory over-axle pipes.

That might make a difference with someone who is on a limited budget. They could purchase headers and an X pipe down the road after upgrading their mufflers from the stock units, potentially saving hundreds of dollars and roaring down the street in the meantime.

 

Mustang Over Axle Pipes

The pipes that run from your H pipe, “over the axle” and connect to your mufflers are so named. Honestly, there’s not a lot going on here, but since they are part of the system as a whole, it’s worth talking about them. They’re usually swapped out because fancier exhaust systems provide replacements that are “mandrel bent” to avoid any rippling in the pipe itself.

Again, I’m not completely sold on how much power can be scavenged from this type of construction, but you can’t argue that it does provide a smoother bend for the exhaust gasses. There are many Mustangs on the road that still use their stock over axle pipes without any issues.

Most of the benefit from replacing these comes from the weight savings I mentioned above. A nice pair of these in a lighter weight steel will save a handful of pounds in total.

 

Consider Deleting Your Resonators

Resonators are chambers in your exhaust system that dampen the sound coming out. This is essentially how manufacturers get rid of drone. You see, depending on how hard your engine is working, that exhaust gas is trying to come out as fast as it possibly can and can sometimes make a specific resonance based on the vibration of the exhaust system itself. This gets a bit technical but just know that it’s a muffler for a specific type of sound.

Our cars come with two smaller resonators on each pipe after the H pipe. This is a bit different than older-style resonators that were integrated into the H pipe, itself.

The reason I mention these is that most people cut them off to get a throatier sound and increase volume. In their place, they have a muffler shop weld in another piece and away they go. I’ve seen lots of people remove them and very few complain about not having them or are trying to put them back on.

I’ve never heard, “Wow, I really wish I still had my resonators! I’m going to have some welded back on.” Larger exhaust kits that include over axle pipes don’t have them at all. This small mod might be for you if you want to make your car a screamer.

 

X Pipes vs. H Pipes

So we have our headers coming off of the engine combining into a single pipe that then moves through your catalytic converters and into your factory H pipe. Automotive guys are simple and it is simply named after its shape.

H pipes are preferable in our cars due to the tone that they make. Many say that they make a low rumbling sound and provide a cleaner tone.

X pipes are sold by a lot of aftermarket vendors. The shape of this crossover pipe is sold as a performance item due to the fact that turbulence would be reduced as the 90° angles of an H shape are removed in favor of a simple cross. While this makes sense to me, I cannot vouch for the performance gains, as stated above.

One drawback of the X pipe is the tone that it produces as the exhaust gases rumbled through the exhaust system. The sound seems to be of a higher pitch and quite a bit more raspy than the H pipe. While there may be some minimal gains in changing to this shape, I can’t recommend it.

 

The Boss 302 Side Exhaust

Although weight isn’t going to be on your side here, there is one wildcard I wanted to mention. The S197 special edition Boss 302 came with a very unique exhaust set up. The H pipe, the pipe that equalizes exhaust pressure between the left and right banks of the engine, was unique to this car.

From the factory, it provided two exhaust outlets that exited directly in front of the rear tires. Each pipe has small restrictors from the factory with about a half-inch hole that limits the exhaust gases from escaping through these outlets. It lets out just enough to make some extra noise. Heavenly noise.

The sound kind of emanates from all around the car instead of simply out the back. A friend of mine called it more “authoritative” and is something you may want to look into if the sound of your car and tone is a high priority to your exhaust system choice.

As I mentioned, I’m not doing myself any favors in the weight department and some essentially adding extra piping to my exhaust system, but I think it’s worth it due to the incredible sound and symphony that plays when decelerating in second gear.

 

The GT500 Mufflers

Quite a few Mustang owners opted to go for the Ford performance GT500 mufflers. If you are not interested in cutting your rear bumper and adding the valance, Ford Performance sells these with only a single exhaust tip instead of the dual tip. These are my personal preference not only for outputting a reasonable volume but also for tone. I get a lot of compliments on them.

As a pro tip, I would like to mention that eBay is an excellent place to find GT500 mufflers. I purchased some like-new mufflers from a gentleman who put a performance kit on his Shelby and attached them myself. They literally clamp on exactly where your existing mufflers did and all the mounting points match up perfectly.

 

A Word on Exhaust Tips and Valances

The S197 Mustang has had a few rear valance changes over the years. Most cars came with and continue to use their factory dual exhaust valance. This provides outlets for two exhaust pipes, one for each side.

Some years of GT500 Mustangs came from the factory with dual tipped mufflers and a rear valance that accommodated the extra room needed for two tailpipes on each side. Ford Racing provides a part to purchase this valance. You can get it from any Ford Dealer or Tasca, if you prefer.

Regarding your rear bumper may seem scary, but it’s a simple job. If I can do it in my driveway in one day, you can, too. Believe it or not, the valance actually snaps in once you cut part of the bumper away, just like it did at the factory for GT500s. Everything is already pre-marked, too. An hour or two tops.

Finally, Roush also sells a rear valance to go along with their custom exhaust tips. The exhaust kit that they sell that include square tips fit perfectly inside of the bumper for a completely custom look. The first time that I saw these, I fell in love, but ultimately went a different direction.

 

Conclusion

There is no such thing as the best exhaust system for Mustangs. There, I said it!

There is only the best exhaust system for your Mustang.

The best advice I can give is to hop on YouTube and listen to some Mustangs with headphones. Receipt of the Mustang in a parking lot chat him up and ask him what exhaust he has asked him to rev it a few times. I’m sure he would be more than happy to oblige.

 

Related Questions

Can you change just the mufflers? Yes, of course. Most aftermarket mufflers bolt right up to your stock over axle pipes. You shouldn’t have a problem with any major brand. A muffler shop will be happy to help you on the cheap, especially if your stock exhaust parts are in good condition.

Do I need a tune when changing exhaust? If you’re just changing the H pipe or components after it, you don’t need a new tune. The only time your car will benefit from a new tune if you’re removing your catalytic converters. Your O2 sensors will throw a check engine light and can be disabled by your tuner, even if the car won’t pass emissions.

Are titanium exhaust systems worth it? Honestly, I’ve never seen one or met someone who has one. Stainless steel exhaust systems will already save plenty of weight. You’ll start running into diminishing returns with anything more expensive.