Mustang "Best Exhaust" Guide

As we know the S550 or S650 Mustang needs an aftermarket exhaust to "release the beast" inside especially to unlock an authentic V8 sound. However this is equally true if you want to give your Ecoboost a sporty tone too. This is especially true of the early 2015-2017 pre facelift Mustangs, which were super quiet from the factory. The 2018+ facelifts and 2024+ S650s have active valved exhausts which sound good already, but can still be greatly improved with a simple change. However as a down side the 2018+ and S650 2024+ also have GPF (Gas Particulate Filters) which make can make certain changes more complicated As such, one of the questions we encounter most is; "what is the best exhaust for MY mustang?". Well here is our answer:

"It Depends"

This isn't very helpful in itself, but what might help you (hopefully!) is this brief guide to why it depends & what factors can help you make your decision, we hope it helps a little. Remember you can always ASK Steeda UK for advice if you need.

The factors involved in choosing an exhaust:

There are a number of variables & choices facing you when it comes to picking the right exhaust for you. One thing to remember is that certain factors are totally subjective, & others are empirical. For example, "What sounds nicest?" is totally subjective (i.e only YOU know the answer), whereas some performance issues are empirical, e.g. an "Axle Back" system won't really aid performance but a catback / full exhaust system will.

Price too is empirical!

Some of the Terminology you might see:

• Axle Back or Cat Back
• Headers / Downpipe / Exhaust manifold
• H pipe or X pipe (or HEX!)
• Street System or Competition System
• Resonated or Non Resonated
• Cat
• GPF (Gas Particulate Filter)

PART 1 We look in detail at what can be a bewildering array of terms

"Axle Back" exhausts refer to a shorter system that replaces the very rear of your exhaust, usually from the rear axle (wheels) backwards. They are a cost effective solution as they are cheaper than a catback system, & are usually the best way to get a nicer look & change the sound of your Mustang, if you aren't looking for performance.

NOTE: on 2018+ Facelift cars and 2024+ S650s the rear mufflers contain the active exhaust valving, so its essential to either buy an active valved replacement or a system like the AWE Valve bracket to stow your valve plugs if you delete the active system.

The Steeda  Aggressive Axle Back (above) offers aggressive noise adding drone free rear mufflers & great looking tips to release your V8 rumble for a 2015-17 S550 Mustang. We also offer a quad exit non active version for 2018+ cars. 

Borla offers active valved axle backs with polished or black tips (as below)

NOTE: With Axle Back system you will normally have to CUT the OEM exhaust in order to insert the new rear section you want to fit.

"Cat Back" exhausts refer to what is the 'standard type' when referring to an aftermarket system. These usually run as the name suggests from AFTER the factory catalytic converter (cat) through to the rear of the car, so are longer than axlebacks & hence more expensive. Catbacks offer a better flowing exhaust solution, helping your engine to breathe better, & providing a boost in performance, as well as the looks & sounds gains offered by the Axle Back systems above. They also allow further expansion of the system by connecting directly to aftermarket Headers or Downpipe for a full exhaust system for optimal gains.

The Magnaflow Competiton Catback above shows the smaller silencers on offer on "Competition" systems, & also Black tips for a different look, as well as an X pipe at the front end of the system. As you see its a lot larger than Axle back systems.

As catbacks replace the  entire length of the exhaust they can use larger diameter piping. The OEM exhaust is 2.5" / 62.5mm whereas aftermarket system are often larger at 2.75" / 69mm  or even 3" / 75mm. This can optimise flow especially when more power is wanted.

"Headers" or "Downpipe" or "Exhaust Manifolds" refers to the section directly off the engine block & can incorporate factory replacement catalytic converters, hi flow performance cats, or cat delete sections. These are added to a catback system to provide the ultimate in performance gains, & often need accompanying engine tunes to be fully effective. In the case of Turbo cars, like the Ecoboost Mustang, often a tune is required when adding a full exhaust including a downpipe & high flow cat. Headers more usually refers to the exhaust manifolds on a normally aspirated car, whereas a downpipe often refers to a turbo car.

The pictures below show Kooks V8 long tube header system with high flow cats   

& bottom CP-E Ecoboost decatted Downpipe
                  

NOTE: in 2018+ facelift S550 Mustangs and 2024+ S650 Mustangs all the European edition cars come with GPF filters embedded in the exhaust manifold prior to the catalytic converter. This means replacing them with a non GPF equipped aftermarket system will throw warning / error lights (CEL) and cause the car to enter limp mode. This is why we recommend not changing the headers on any 2018+ car unless its for specific race /off road use.

"X pipe or H pipe or HEX pipe" are terms that refer to V8 exhausts only. It is the section at the front of a catback system, replacing the OEM silencer with a section that either cross flows exhaust gasses (X pipe) or has a lateral connecting pipe between the two sides of the exhaust (H pipe). Preferences differ but as a guide, an X pipe will provide a raspier more "race car" sound & more top end performance, while an H pipe will produce more of the classic V8 rumble & slightly better performance in the lower end. The HEX pipe is a new combination mode featuring both the H and X crossovers.  

These can be a popular mod for the 2018 + Mustang and 2024+ S650 Mustangs as their active exhaust sounds very good from the factory so all that some people want is a slight change in tone or volume that an X or H pipe (or HEX) can provide...

Steeda H pipe section,& below Steeda X pipe section then HEX PIPE
            

NOTE: these are sometimes referred to generically as "resonator deletes" as they swap out the central resonator ont he car. Also note these will require cutting the OEM exhaust pipe to remove the OEM resonator.

"Street or Competition / Resonated or Non-Resonated" refer to the type of silencing & are interchangeable, depending on manufacturer. Generally a "Street" or a "Resonated" system will be more civilised / quieter with less chance of resonance / drone when cruising, whereas a "Competition" or "Non-resonated" system will have smaller or zero silencing for a more raucous tone. The reasoning behind the "competition" name is no silencing should provide no impedance to exhaust gas flow & the benefit of a lighter weight however these benefits are marginal compared to the increase in volume produced!

NOTE: Comp systems might sound track focussed, but if you want to go on the track for track days etc, you might want to make sure its not TOO loud or you might be prevented from using a lot of tracks which often have strict noise regulations (boo!)

"Cat" is short for Catalytic Converter, a system designed for EU emissions testing.

PART 2 of Steeda's "Best Mustang Exhaust" Guide :

Now we have run through the terminology and choices involved in choosing your exhaust in part 1 we can look at how to choose what is right for you.

Some factors to think about when making your choice:

• Is Performance Important?
• Is Style your main concern?
• Is the car for the street or will it be used on trackdays
• H pipe or X pipe?
• Daily Driver or Weekend "fun car"
• Noise levels, loud or more civilised?
• How it sounds?
• Cost
• Upgradability 
• 2.5" or 2.75" or  3" system

How do you want your car to sound?
If all you want is a better muscle car /sports car sound and a different look, then we say its axle back all the way. As part 1 showed, you can get loud or quieter (or crazy loud!) with either black or polished tips on offer, all for less than £800 inc vat
.

If you have a 2018+ car or 2024+ then perhaps just an X or H pipe is all you need....

How do you want your car to sound? One man's (or woman's) too loud is another's too quiet.....

We recommend listening to cars on video and in real life whenever you get a chance, at shows and meets etc. Videos can help but never show what a car is like "in real life". Even standing outside while one revs is just a guide, as until you have lived with it, and driven it in your driving style on your roads, then you won't really know. Hey, we never said choosing would be easy!

Sound will also change a little after first installed so NEVER rush to judgement! Live with it a few hundred miles until it beds in and cokes up. Also tuning and intakes can change the sound as can adding a front end to a catback system. One driver might complain of resonance on a certain system, but another driver with the same car might not hear it at all due to driving differently and indeed hearing differently! All ears dont hear the same....

One vital and often overlooked question is "Do you intend to take it to the track?"

In the UK  MANY tracks have increasingly strict noise limits and competition systems will often make sure you will be black flagged (i.e thrown off the track) or prevented from even starting. Check with your track, as even "Street" systems won't guarantee a pass. In fact some cars with OEM systems wont be allowed on some of the UK's stricter tracks! (Not applicable to Mustangs though I believe).

Performance Choices:

Performance wise all reputable systems will work more or less similarly, aside from differences such as x pipe or h pipe (see part 1); full system or catback; or 2.5" or 2.75" / 3"

A 2.5" system is not usually our preferred performance option but chosen by Ford Racing for its more OEM type performance and quieter output. Those looking for bigger power, especially those aiming for full exhaust systems or thinking about forced induction upgrades (turbo or supercharger) should certainly go for a larger 2.75" (69mm) or 3" (75mm) system.

On full systems, you can choose hi flow cats, or even decatted systems, which can improve flow and hence performance, but be aware that decat systems are generally referred to as "off road" systems (i.e for track use) as local laws can mean they are not legal for road use. Most high quality hi flow cat replacements will pass emissions testing and offer almost the same levels of performance as decats. Full systems often require a remap to obtain the full benefits from the hardware and turbo cars such as the Ecoboost will often require a remap in order to use a full performance exhaust system. Kooks systems (pics below) are a great choice for those considering a full system. Also there is no need to do a full system all in one hit. You can certainly start with just the catback and add the "front end" later on. in fact that's a course we recommend as you may be happy with the sound and performance boost just by adding a catback system.

Cost:

Costs can vary but for a quality catback for a Mustang prices start around £1398 inc vat  (The Steeda 3" catback is a GREAT price!) and can go up towards £3000+ depending on system choice. Milltek for example offer a quad tip system which requires fitting a custom rear valance to accommodate the extra tips, and offers a choice of polished, cerakote black or titanium tips. (as below pics)

We fitted a 2024+ Milltek active catback  on the Q767 Dark Horse we built with Nankang and Misha Charoudin

Quality V8 Headers can vary in price with cat choices, with X Force headers from Australia offering a great price from €1199, through to the super high quality Kooks systems from €3300 + dependant on choices. Ecoboost down pipes can be from around €600 decatted & upwards depending on cat etc

The X force headers are section welded as opposed to the Kooks mandrel bent systems so the price difference isn't just the brand name, its both the material and the manufacturing process that can be different. 

As mentioned previously the lowest cost option is an H pipe or X pipe option at only £299 inc vat.

Steer clear of budget exhausts as they are often badly designed or made from inferior materials or offer poor fitments. A good performance exhaust should offer effectively managed exhaust gas flow. Budgets systems can often harm performance through poor design. Or just sound terrible and fall apart quickly...

CONCLUSIONS!

It's not simple is it! YOU have to decide and many of our customers will own up to either changing their minds later on or deciding to change tone, or simply feeling they made the wrong choice initially. For example some Mustang owners LOVED their thunderous exhaust initially but after 6 months of loving it, and using it as a daily, it began to wear on them, and they wanted something quieter. For others a "sensible" option was not radical enough, and after hearing more lively set ups they decided to switch to a more raucous system,

Don't be afraid to jump in. After all its like painting a room, if you dont like it you can change it later! If you do decide to change you can always sell your original system to someone else! Also remember with all car modification and personalisation. It's YOUR car, so if YOU like what you have, who cares what anyone else says! The other thing to remember is that most quality systems, regardless of which one you get, 99.9% of the time you will like more than stock!

A little video we made to help: (with just a few of the options). There are loads of videos on the main Steeda youtube channel so jump in there too!