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Flowmaster Outlaw Cat-Back Exhaust (15-17 GT Fastback)

AmericanMuscle no longer carries the Flowmaster Outlaw Cat-Back Exhaust (15-17 GT Fastback). Please check out 2015-2019 Mustang Cat-Back Exhaust for an updated selection.

Features, Video & Details

  • Super Aggressive Flowmaster Outlaw Sound
  • Durable 409 Stainless Steel Construction
  • 3" Mandrel-Bent Tubing
  • 4" Polished Stainless Steel Tips
  • Includes X-Pipe and Two Flowmaster Outlaw Mufflers
  • Fits 2015-2017 GT Fastback Mustangs

Review & Installation Video

Review & Install Video

Hey everybody, I'm Justin with AmericanMuscle.com and welcome to my quick breakdown of the Flowmaster Outlaw Series Catback Exhaust System, available for your 2015 Mustang GT. As you all just heard, the Outlaw's going to deliver that signature, aggressive Flowmaster sound, thanks largely in part to the patented Outlaw Series mufflers here, one of the loudest offered by Flowmaster, in addition to the removal of the factory resonator. The Outlaw Series mufflers here were actually born and bred for racetrack purposes, where the demand for a lightweight, free-flowing muffler was needed, to tame those crazy volume limits of the open headered sprint cars. Now, this thing became so popular that Flowmaster started incorporating it into some of their more mainstream, consumer exhaust systems, and as a result, it's been one of their top sellers ever since. Replacing that big, goofy suitcase-style resonator here, you're going to find Flowmaster's patented scavenger-style crossover pipe, which is going to take the place of a more traditional X or H pipe. Now, according to Flowmaster, this thing actually produces a little bit more low-end torque than some of those more conventional mid-pipe designs, and it's something that you're going to find with the majority of the Flowmaster Catbacks available for your Coyote-powered Mustang. Getting into some of the details here with the Flowmaster Outlaw Series Catback, you're going to find a full 100% stainless steel construction throughout, three-inch mandrel bent tubing, in addition to these Outlaw Series mufflers here, which as you can see, are done up in the Flowmaster traditional black. Finally guys, four-inch slash cut tips here, embossed with that Flowmaster logo. Unlike the majority of other catback offerings for the 2015 Mustang, there is a small amount of cutting needed to get the Flowmaster Outlaw Series Catback bolted up to your ride. So with that said, be prepared to break out the Sawzall and the eye protection when it comes time to get down to business. Thanks to Flowmaster's detailed instructions, they lay out everything where you need to cut, and you can expect to be making noise in less than three hours from start to finish. So if you're one of the many Mustang owners out there who swear by the Flowmaster name, then be sure to check out the aggressive sounds of the Outlaw Catback for your GT right here at AmericanMuscle.com.

Super Aggressive Flowmaster Sound. Give your coyote powered S550 Mustang Fastback that unmistakable Flowmaster sound with the Outlaw Series Cat-Back exhaust system from AmericanMuscle. This system improves exhaust flow using Flowmaster's race-oriented style Outlaw mufflers for that super, aggressive exhaust note your high powered Pony deserves.

Race Car Growl. The included X-Pipe not only helps increase power, but it also adds a loud raspy, race car growl to the sound of your exhaust with its modern "X" crossover pipe design.

Stainless Steel Construction. Constructed from durable 3" 16 gauge 409 stainless steel tubing for it's corrosion resistant properties the Flowmaster Outlaw Cat-Back features two race-oriented mufflers with massive 4.0" diameter polished stainless steel tips for impressive muscle car looks and sound. As an added bonus, the tips are embossed with the "Flowmaster" logo for true custom styling.

Application. This Flowmaster Outlaw Series Cat-Back exhaust system is designed to fit the 2015-2017 GT Fastback Mustangs equipped with the coyote 5.0L DOHC V8 engine. Not compatible with convertibles. Reuses the stock hangers for installation.

Fitment: 2015 2016 2017 Details

MPN# 817734

CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

What's in the Box
  • (1) Right muffler assembly
  • (1) Left muffler assembly
  • (1) X pipe assembly
  • (1) Right intermediate pipe
  • (1) Left intermediate pipe
Installation Info
Tech Specs
Cat-Back Exhaust Specifications
Piping Material: 409 Stainless Steel Tip Material : Polished Stainless Steel
Piping Size: 3" Tip Size: 4.0"
Muffler Type: Straight-through Fitment: 2015-2017 GT Fastback
Will it fit my Mustang?

    Customer Photos (12) Submit Your Photo

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      Questions & Answers (14)

      5 Top Rated Questions

      Will this setup bolt on to kooks long tube headers 1 7/8 off-road catless headers?

      • Yes, the long tubes have the correct adapter pipes attached already so you will be fine.

      Helpful (2)

      I have put this exhaust in my 2016 mustang 5.0, and I have noticed that my fuel economy drop down by half, is that normal or do I need something to fix this like a good air intake kit ?

      • A cat-back exhaust will not play any part in fuel consumption. Due to the change in the exhaust sound, that can make you stay in the gas longer than you normally are but cold air intakes along with a tuner can be a good remedy for fixing fuel consumption.

      Helpful (1)

      I am looking at getting an S550 Mustang soon and I had this same catback on my 2013 GT before trading it. The issue I had with the outlaw is that it produced a horrible drone around 1900-2000rpm. Does this set up still have that same drone?

      • I have had this catback system on my '15 GT for ~9 months and I couldn't be happier, but yes, this does have a noticeable drone around that rpm range.

      Helpful (1) Show 1 more answer

      Ever since this was installed onto my 2015 Mustang GT Premium i have been throwing a CEL for Random Multiple Cylinder Misfires and misfires on cylinders 3, 5 8. Whoever owned this before me installed a C L intake (I think the tune required) but possibly didn't tune the car. Did this exhaust throw it over the edge and now i need to tune car to fix issue? I know this light never came on prior to this install....

      • This should not require a tune and we would recommend having the vehicle looked into directly by a local shop in your area in order to verify the issues with whatever codes are being thrown.

      Helpful (0)

      Can an H Pipe be used instead of an X Pipe for this product? And do you have any recommendations on a compatible H Pipe if so?

      • At this time we are unaware of any H-Pipes that are compatible with the Flowmaster Outlaw Cat-Back Exhaust.

      Helpful (0)
      Post Your Question
      9 More Questions
      If I get an x-pipe with for my v6 mustang can I get a shop to weld this gt exhaust to my 2017 v6 mustang? 1 answer
      any horse power gain from a 3in cat back 1 answer
      Will I have to do some cutting for this to fit my 15 mustang? I saw two people comment in the reviews saying that they had to. 1 answer
      Will this fit on a European spec GT Fastback, the right hand drive model? 1 answer
      Can this exhaust fit with long tube headers and if so what headers will fit this? 1 answer
      Is an o2 extension kit required for this catback? 1 answer
      Can anyone recommend a good set of headers that would compliment this exhaust? Thanks 1 answer
      Will this setup bolt on to a set of long tubes?? 1 answer
      Does this exhaust require a tune? I know its always recommended, but last time my x pipe was really raspy, and after the tune it calmed down. Wondering if this is the same case. Thank you 1 answer

        Customer Reviews (48) Write a Review

        Overall Rating 4.8

        out of 5 stars

        Installation Time:Full Day

        Installation Cost:$100-$250

        • Loudness / Volume 5 5
        • Exhaust Note 4.826087 4.8
        • Fit & Finish 4.717391 4.7
        • Bang For Your Buck 4.73913 4.7



        • 5/5

          Installation Time: Full Day

          April 23, 2019

          Give Yourself a Presence

          The product was a bit difficult to install. But it sounds great and is very loud. If you dont have a soundproof garage make sure the neighbors like you before purchasing.

          TerryR

          Year: 2017 Submodel: GT

          Helpful (0)

        • 4/5

          Installation Time: Full Day

          February 28, 2019

          Very loud, classic mustang sound

          Great exhaust. Has drone, a lot of it. If you don’t mind sacrificing drone for exhaust sound you won’t be disappointed. Sounds like the 2011-2014 GTs

          Tiogioo

          Year: 2016 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Full Day

          January 26, 2019

          Loud and mean

          It took a day to instal and it was well worth it. She is loud and mean with every shift. Everytime im at a red light people always give me compliments.

          RobertS

          Year: 2016 Submodel: GT

          Helpful (3)

        • 5/5

          Installation Time: Less than 1 Hour

          January 05, 2019

          Great buy!

          Loud and has slight drone but doesn’t bother me any . Going to be hated in my area when I install long tubes in the summer . No fitment issues, my friend and I had it done in about a hour .

          Chris

          Year: 2016 Submodel: GT

          Helpful (4)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          October 24, 2018

          Best Exhaust System

          If you want that old school muscle car sound this the product for you notice a increase in performance from the beginning

          QuentinL

          Year: 2015 Submodel: GT

          Helpful (5)

        • 5/5

          Installation Time: Afternoon

          September 17, 2018

          Face Melters

          This exhaust produces rich, deliciously audible notes that will have you more worried about smiles per gallon as you gulp up apex after apex. Burble, check. Growl, check. Envious bystanders, check. You’ve seen the YouTube videos. You already know you’re buying it. Just do it already.

          Joe

          Year: 2017 Submodel: GT

          Helpful (8)

        • 5/5

          Installation Time: Afternoon

          August 16, 2018

          It sounds like freedom

          Picture George Washington singing the National Anthem while crossing the Delaware. Thats what it sounds like everytime you get on it. This exhaust is loud, in your face, and does not care about the people around you. Absolute must have for any mustang owner who loves to announce their presence. Side Note: There is a decent amount of drone cruising in 6th Gear at 2K. Its a trade off but I am more than happy to pay it to have my car sounding as amazing as it does.

          kiszler

          Year: 2015 Submodel: GT

          Helpful (8)

        • 5/5

          August 16, 2018

          Worth every penny!

          Full Review/Expereince with some tips. Shop install takes an hour and a half. From what they told me the fit was very well and they had no trouble with it (comes with instructions) and charged me $60. So if your shop tells you they’re having trouble they might not know what they’re doing. First start up after the install is extremely intense, you really get that aggressive sound you’re looking for so you should be extremely satisfied as the video doesn’t do the sound any justice, I was honestly shocked. People will definitely be breaking their necks trying to find the monster they hear driving down the road, it sounds that amazing! With that being said, the drone is absolutely killer, so don’t put this on something you’ll be driving every single day or you’ll regret. I drive my CS/GT around 10 miles a day on average. If you drive your GT over 40 miles/day you should really consider looking at something else because it feels like you’re in a commercial jet and will leave your head busting after a moderate drive. Avoid 100 mile drives at all costs! I’ll clear this up on a final note for those that live in an apartment or anywheres where you have a lot of neighbors. Expect complaints, yeah, seriously. I’m in an apartment while at college and the cold start blares so loud that I feel the need to hop in the car and get out of there as quickly as possible so break this in with your neighbors and tell them you’re not being this loud on purpose and hope they’re nice and understanding like mine because you’ll be heard within a 40-50 yard radius, no exaggeration. Summarized : If you’re worried about being too loud in your quiet neighborhood and take long daily drives, sorry to say but this won’t be for you, just a friendly warning. If not then this will be the best exhaust system you could ever have on your mustang!

          KJ

          Year: 2016 Submodel: GT

          Helpful (6)

        • 1/5

          Installation Time: Afternoon

          July 24, 2018

          Outlaw Catback

          Without going on a long rant, I’ll break it down nice and easy. The exhaust sounds amazing, high quality materials. The fitment is trash, I cut precisely as directed per the instructions and played endlessly with the exhaust and can not get the exhaust tips to line up for the life of me. I took it to multiple exhaust shops and they can not line the tips either, they stated kits are always like this. I would recommend just buying the mufflers and getting a custom exhaust built for better fitment than this kit.

          Daniel

          Year: 2017 Submodel: GT

          Helpful (8)

        • 5/5

          Installation Time: Afternoon

          July 06, 2018

          Great Exhaust

          I was looking for something that would be loud and unique and I found it. This was amazing its super loud but also sounds really amazing. Much better than the factory exhaust. It took some time to install because had forgotten that I needed to cut off some of the old pipe. Just make sure if you get this you are aware you won't be able to go back to the stock exhaust because you have to cut some of the pipe off.

          LawsonW

          Year: 2016 Submodel: GT

          Helpful (6)

        • 5/5

          Installation Time: Shop Install

          May 22, 2018

          Best sounding exhaust ever!

          had this system installed on my 727hp Roushcharged '17 GT. Everything I wanted in an exhaust system. Loud. Obnoxious. And when I drive to town everyone knows it. I didnt buy a supercharged Mustang to please anyone but me. And the way the outlaw catback makes my GT sound...is pure fun. I dont care what anyone tells you, This is the best bang for the buck exhaust out there.

          EARACHE

          Year: 2017 Submodel: GT

          Helpful (7)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          May 08, 2018

          The Outlaw

          I had the system installed at a local shop that a friend made me aware of and had it installed in my 2017 GT for $120.Designed for sprint cars it is on the loud side at higher RPM's.There is a slight drone at highway speeds but since installing them I've gotten MANY compliments on the sound of the exhaust.If your looking to wake up your GT this is a great mod !!

          ShawnL

          Year: 2017 Submodel: GT

          Helpful (6)

        • 5/5

          Installation Time: Afternoon

          April 23, 2018

          Absolute Beast

          I ordered my Flowmaster Outlaws on a Monday afternoon, they were delivered on Wednesday, and by Thursday afternoon my 2017 GT was turning heads. I couldn’t be more pleased. The sound is a deep growl and is better than I imagined.

          Mike

          Year: 2017 Submodel: GT

          Helpful (5)

        • 5/5

          Installation Time: Less than 1 Hour

          March 24, 2018

          Exhaust

          Louder than the video buy it turns heads and breaks necks at times.

          MarkD

          Year: 2016 Submodel: GT

          Helpful (5)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          March 13, 2018

          Amazing sound! The way the 5.0 should sound.

          This has a very nice aggressive sound very loud. Other reviews had some points in there about the drone, but honestly it’s not bad at all, barely noticeable. If you want to turn heads and have that nice distinct sound I suggest going with the outlaws. Definitely worth it. Shop install was in between 2-3 hours, wasn’t in any hurry that day anyways. $150 was the price.

          MambaDavid24

          Year: 2017 Submodel: GT

          Helpful (6)

        • 5/5

          Installation Time: Afternoon

          March 02, 2018

          RAW OUTLAW

          Me and a buddy installed these on my 17 GT S550 In about an hour and a half. Tips are a pain to get perfect. Other than that it was pretty basic. Definitely worth it! I originally was going to go with a different system...less aggressive. SO glad I didn't. I can honestly say I have not heard anything louder or better. I read up on multiple systems and am positive I made the right choice for me. I will say this, these are NOT for everyone. They are LOUD! The drone isn't as bad as others say...at least for me. However I can understand the claims. It all depends on the individual. I personally LOVE everything about it. Bottom line...if you want the nastiest sound around these are it. Go big or go home!

          MatH

          Year: 2017 Submodel: GT

          Helpful (6)

        • 5/5

          Installation Time: Less than 1 Hour

          January 31, 2018

          Flowmaster with Corsa Double X Pipe

          I have this Flowmaster connected with the Corsa Double X pipe and there’s no comparison to the Standard flowmaster set up. If you have this already, get The Corsa Double X pipe connected to it. So much better than this as is.

          CarmineB

          Year: 2017 Submodel: GT

          Helpful (6)

        • 1/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          December 29, 2017

          Ruined My Stang

          The review section for this product really let me down. I was looking for the deep muscle car sound of long ago, and I was sadly disappointed in this cat back system. Going from stock to this resulted in pressure inside the cabin around 2000 rpms that was incredibly painful to drive in. The drone is insane, much worse than other Flowmasters I have owned. BEWARE, there is no video that will describe the drone, as the low frequency will not come through accurately on any video. My brother commented that he felt as if he had been "punched in the earhole" after a short test drive. Not what you want happening to the passengers/drivers in the car. Do not put this system on a daily driver.....you have been warned. No noticeable throttle response improvement. This cat back system was professionally installed and then subsequently checked for a bad installation by a Ford service center. Uninstalled and sold on Craigslist for a loss after less than 50 miles. Don't ruin your new Mustang like I did. Stay away from this cat back system.

          JamesG

          Year: 2017 Submodel: GT

          Helpful (10)

        • 5/5

          Installation Time: Less than 1 Hour

          December 01, 2017

          Holy drone Batman!!!

          This exhaust, hands-down, has completely transformed my cars attitude!! I absolutely love it!!! The drone is pretty intense but I personally don't mind. Everyone that hears my exhaust, even other Mustang owners, are asking me what it is because it sounds fantastic!!! Most of the drone is easily fixable with some Dynamat.

          Joe

          Year: 2017 Submodel: GT

          Helpful (5)

        • 5/5

          Installation Time: Afternoon

          November 02, 2017

          Amazing

          Took these to a local shop and they installed them, took maybe 3 hours total. This exhaust is extremely LOUD! I never expected how much of a difference these could make. Don't buy these if you don't want to wake up your entire neighborhood!

          Brian

          Year: 2017 Submodel: GT

          Helpful (5)

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