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Will I Gain More Horsepower With An Exhaust System?

After-market exhaust systems are almost always less restrictive than factory exhaust systems. However, that doesn’t mean that adding an after-market exhaust will always result in more power. Depending upon your vehicle and the system you choose, an after-market exhaust can add as much as 50 horsepower or as little as 2 or 3 horsepower. Here’s how you can figure out what to expect:

Don’t Focus On Horsepower Only

How to calculate horsepower

Horsepower is calculated by multiplying torque by RPM. Therefore, if a new exhaust system adds just 10 lb-ft of torque at 5,000 RPM, that will result in a horsepower increase of 9.5 hp. While that might sound like a solid horsepower gain, an extra 10 lb-ft of torque at 5,000 RPM usually doesn’t do you a whole lot of good in day-to-day driving. After all, how many of us run our engines at 5,000 RPM on a constant basis?

Throw Exhaust System Manufacturer Estimates Out the Window

Because horsepower is a function of RPM, it’s very easy to show big horsepower gains on paper. Diesel trucks are a great example – because they generate gobs of torque anyways, adding an extra 35 lb-ft of torque at 3,300 RPM results in a gain of 23hp. This number may seem impressive, but an extra 35 lb-ft of torque at 3,300 RPM isn’t that useful to your typical diesel truck owner. It’s a good increase to be sure, but it’s not usable power.

The other reason that you shouldn’t put a lot of stock in manufacturer estimates is that dyno results are fairly easy to manipulate. When a vehicle is tested on a dyno, there can be significant variations from test to test without any change to the engine. If a manufacturer takes their worst run from their “before” tests and their best from “after” tests, they can show a really big gain that’s mostly due to normal variations between runs.

In other words, exhaust system performance estimates are always very generous. If the kit from Flowmaster supposedly adds 8 hp and the kit from Magnaflow supposedly adds 13 hp (or vice versa), chances are good that both perform pretty close to the same.

The Most You Can Gain is 2-5%

If you want to know how much power you can expect to gain from adding an exhaust system to your car, assume that your engine will get 2-5% more powerful. More specifically, large engines like a big 6.0L V8 typically see about a 2%-3% horsepower increase. Smaller engines, like a 1.8L 4-cylinder, typically see a 3-5% horsepower increase.

Exhaust systems add power when combined with air intakes and programmers

HOWEVER, exhaust systems have a multiplying effect if you combine them with other add-ons. The exhaust system by itself won’t add a lot of power, but combined with an air intake and a performance chip or power programmer you could see a significant increase in performance. You’ll also see a slight increase in fuel economy (assuming you keep your foot out of it, of course).

Remember That The Intangibles Have A Value

Adding an after-market exhaust system to your vehicle isn’t just about adding some more horsepower or improving fuel economy. You’ll enjoy a sportier exhaust note, better throttle response, and hopefully driving will be just a little more fun.

Considering how inexpensive an after-market muffler is, it’s a nice way to customize your vehicle on a budget. The icing on the cake is slightly more power and improved fuel economy.

43 Comments Post a comment
  1. Mike Murdoch
    Feb 22 2012

    honest grass roots, readable and not over the top techo tripe, well done

    Reply
    • Jason
      Feb 22 2012

      Thanks!

      Reply
  2. Randy
    Apr 19 2012

    How much are those programmers?

    Reply
  3. justin
    Aug 1 2012

    if im runnin an after market muffler which is a flowmaster should i install a high performance intake also?

    Reply
    • Jason
      Aug 2 2012

      justin – There’s definitely an advantage in upgrading both your exhaust and your intake, and I would recommend both. Even if you just add a performance air filter.

      Reply
  4. Sylvain
    Apr 30 2013

    Hi

    Thanks for your article :)

    Any idea about the gain with the combo you suggest?

    You said 2-5% only the exhaust so I guess around 10 with the combo?

    Thank you

    Reply
    • Jason
      Apr 30 2013

      Depends on the engine. As a general rule, the combination of a programmer, exhaust, and air intake can add at least 20hp. The compromise is that your vehicle will be louder and that most after-market tunes require you to run premium fuel.

      Reply
  5. Bob albertson
    Oct 21 2014

    Hello,

    I have a 1977 Chrysler Cordoba with the LA 360 4bbl making a factory 170 HP. I will be putting a pair of chrome shorty headers along with an X-,Pipe 3″ dual exhaust system with a pair of high flow performance mufflers. I will also be replacing the factory cats with after market high flow cats.

    Can you give an idea of an approximate increase in HP and TOURQE?

    I will also be installing a new set of iridium plugs and synthetic motor oil. Also I will be putting in an electronic HGH performance ignition system with the factory air cleaner with a K&N air filter.

    With these changes I given, what kin of HP gain can I expect? The only other upgrade I plan on a bit later, will be a high performance intake manifold with a rebuilt factory Carter thermoquad carburetor. And what type of HP gain from the new t intake give me?

    Thanks,

    Bob Albertson

    Reply
    • Jason
      Oct 21 2014

      Bob – No idea. A 360 can easily make 300hp, and with massaging could jump up to 400hp…but this is an old car with what is (I’m assuming) an original motor. You could very easily stress the motor.

      My advice is to get with the local classic performance shop, ask for some quotes on things, and see what you can learn. You also may find that there’s a rebuild kit for your 360 that boosts power, with new cams, upgraded internals, etc. Good luck.

      Reply
  6. Akthar
    Nov 3 2014

    I have a Dodge Charger 100th year anniversary edition. It has 370 Hp. BY how much will the Hp increase if I add a varex exhaust system ?? I read earlier that if I install Magnaflow exhaust system, I could gain a min of 20hp. Is that true?? Your explanation will be highly appreciated.

    Reply
  7. Moe
    Jan 17 2015

    Ok so hi guys I just bought a 2015 Corolla s 1.8L. Now Its a good reliable car. I’m just trying to gain more hp. And I wanna do that without stressing the engine. I’m just think about getting a exhaust system, intake, and a computer chip. Any suggestions.?? To how how much hp I can gain with that?? Will it affect my engine too much?? It only comes with 132hp. Which is not enough lol. Plz suggest and advise on what should I do.

    Reply
    • Jason
      Mar 3 2015

      Moe – I wouldn’t try anything radical with the newest Corolla, at least not until the after-market releases some parts specifically designed for this vehicle. I’d say you need to wait 12-18 months to see what comes out (if anything).

      Reply
      • Edgar Rodriguez
        Jun 3 2015

        I put a flowmaster muffler to my 2015 corolla and it feels more powerful at running but I do not feel a big diference on takeoff which is what I Don’t like about this car I am going to buy a K&N Typhoon intake specifically made for this type (model) of car I will post what I get

        Reply
        • John
          Jul 20 2015

          hey, I’m thinking about doing the same thing with my 2012 Corolla. Did you get the K&N cold air intake? How’s the performance?

          Reply
        • Jason
          Jul 20 2015

          Edgar – Unless you buy a turbocharger or something, you’re not going to notice a big difference regardless. It’s still a 4-cylinder economy car.

          Reply
  8. girish
    Jun 30 2015

    i got 04 hyundai tiburon GT model. recently i installed cold air intake & it sounds gr8 & take off quick. i’m planning to add G-Force chip & cat- back exhaust system. any idea how much HP it gonna make after installing chip & exhaust in combo? thanks

    Reply
    • Jason
      Jul 20 2015

      Girish – I would suggest that you do not buy G-Force chips. They do not add any power – all they do is mess with the fuel maps. I’ve tried numerous times to get them to provide dyno testing to prove their claims and my requests have gone unanswered.

      But a cat-back + intake will add 10-20hp, all things being equal. Not a ton, but definitely not bad. Just find a quality tuner and you can pick up another 10-20hp.

      Reply
  9. antoni
    Aug 2 2015

    I have a 2002 yukon. I’m putting on headers, cross over pipe new cats and a full cat back system including the muffler. All of it is from Flowmaster. How much of an increase will I see? Will not be doing an intake, next step is a supercharger which is why I got the full exhaust. But the supercharger will require getting a new trans. Stock one can’t handle all the extra power.

    Reply
  10. Yari
    Oct 17 2015

    I have a mustang 2008 v6 . I am adding a shorty pypes headers,AEM cold air intake,True Dual Header Back Exhaust System – Pypes,Ignition Coil Pack Screamin’ Demon and Superchips 1841 F4 Flashpaq. What horsepower increase should I expect.

    Reply
  11. Matt riz
    Dec 24 2015

    Jason you seem knowledgeable I rarely write on these blogs but I have a 2015 f150 5.0 v8 385 hp a little under 400 torque stock. I added a high performance roush cold air intake which I have to say is amazing I’m trying to tell people it out does the k and n but anyway I also put a black dual mbrp cat back exhaust system on which not only looks nice but has added power and sound but not that obnoxious fake noise…I’m a little afraid of tuners and programmers especially how sophisticated these new engines are I didn’t get one and don’t intend cause they buck your warranty and lower the life of your engine but some people swear by them so instead I got a brand new 85mm bbk throttle body I didn’t get the 90mm and that made a huge difference. If I were to guess I’m getting anywhere from 30-50 extra horses that’s my guess acceleration is unreal and my mid-range power is where I recognize the most gains. Any thoughts please feel free to criticize as well haha…I was told my trucks computer will adapt to all of this so I don’t have to make any tunes. Help me out if you can thanks bud

    Reply
  12. TJ
    Dec 24 2015

    so If I calculate this on my car I will gain 172 hp at max output? or am I doing something wrong (obviously) because at 6600 rpm (max output) x 137 = 904200/5252 = 172 hp ????

    somebody please explain I am confused.

    Reply
    • Jason
      Dec 26 2015

      TJ – If you’re referencing the horsepower equation at the top of the page, that’s not a tool you use to predict HP – it’s a formula you use to calculate it based on a torque rating. It’s in the article to show that horsepower is really a proxy for torque at a specific RPM.

      If you read further down, you’ll see that your typical gains in power range from 2% to 5%, with most vehicles coming in closer to 2% than 5%. If you have a 150hp car, your probable exhaust system horsepower gain will be 3-8hp.

      Reply
      • TJ
        Jan 29 2016

        Oh, haha, thanks for the info it’s clear now, it was actually a stupid question coming from me!

        Reply
  13. buddy ferguson
    Jan 23 2016

    I have a 2014 mustang with a 6 I put a roush cold air intake and a cat back muffler by roush it said I didn’t have to change anything in the computer is that right and would I get more horse power. It seems like it did but it could be me

    Reply
  14. Alaa
    Jan 31 2016

    Hello i wanna ask i have mustang GT 5.0 2015
    i added intake K&N + Flowmaster exhaust +program
    can you tell how much horsepower do i gain ?
    thank you

    Reply
    • Jason
      Feb 5 2016

      Alaa – Depends on the specifics. 20hp on the low end. Could be a lot more, depending on the programer and how you measure.

      Reply
  15. Brandon LaBlue
    Feb 17 2016

    I have a 2003 Mustang GT. The current mods on it are BBK Cold air intake, Borla Catback Exhaust, and lowering springs. I was wondering about how much power do you think the cold air intake and Borla cutback exhaust added. I also have a tuner it a BAMA ITSX wireless tuner I haven’t added the tune to the vehicle yet, but do you think that’s a quality tuner in your opinion and how much would that tuner add do you think? I’m also having 3.73 gears installed sometime this week with a JBA Off Road H pipe. I’m thinking that the BBK Cold air intake and the Borla cutback will add about 15-20 combined. I think the tuner may add another 15-20. The off road H I think would add about 5. The gears would not add any, but would improve acceleration and allow to get into power band quicker. Jason, you seem pretty knowledge and any thoughts from you would be appreciated.

    Reply
  16. Chetan
    Feb 18 2016

    Hi Bob,
    I have a Honda Jazz engine L15A1 engine, I have already done a level 1 upgrade, I have installed 4-2-1 exhaust header & want to change stock exhaust system post catalytic converter till the muffler, how much power gains should I expect, the 4-2-1 header highlights 3-4 bhp dyno gains from the manufacturer, how much gains should I expect with changes about above.

    Reply
  17. Berto
    Mar 5 2016

    Yes hi i have an audi a4 1.8t 2001 and im planing off buying an exaust system? But injust read ur combo …so if i just put a muffler and a intake plus a chip…how much hp do i gain.,?. Thanks…

    Reply
    • Jason
      Mar 7 2016

      Berto – Check the dyno charts on whatever you’re looking at.

      Reply
  18. Nathan Holst
    Mar 10 2016

    I have an 2006 Dakota SLT V8 4.7L Quad cab 4×4 . I added the Super Chip programer to the truck, now I can eat any F150’s for lunch at any speed, especially starting at 100km side by side . Next is some custom dual exhaust from the muffler shop.

    Reply
  19. Heather Grossman
    Apr 6 2016

    I drive an 2002 GM duramax, lb7. I have an S&B intake, EFI live (spade) tuner, and an exhaust system with a 5″ tip. I guess I’m a little bit confused on the how calculations work?

    Reply
    • Jason
      Apr 9 2016

      Heather – The calculation in the article is regarding horspower…if you know how much torque your exhaust system adds, you can calculate horsepower.

      But if you’re wondering how much power the exhaust system you already installed has added, I don’t know. Dyno it. :)

      Reply
  20. Drew TL
    Apr 8 2016

    Hey what’s good. I’m whipping a 07 TL Type S 3.5 do you know of any websites where I can find performance headers for my car? Also what performance chip would give me the best HP? Please help me out. Thanks.

    Reply
    • Jason
      Apr 9 2016

      Drew – You can probably buy headers that fit the 3.5L V6 Accord and put them on your TL. I’d check with OBX, DC Sports, Megan Racing, etc.

      CT Engineering too.

      Reply
  21. robert
    Apr 8 2016

    I have 92 camaro L03 170 hp 255 tq. it has a chip, headers with straight one 2 and half inch pipe with flow master with high flow intake. How much hp to I gain? With accel distributor and coil.

    Reply
    • Jason
      Apr 9 2016

      Robert – Dyno it.

      Reply
  22. Daniel
    Apr 10 2016

    I have a 2015 Chevy SS which I put a Rotofab CAI. what exhaust system would recommend for best sound and HP gains. Also would you do headers and exhaust or cat back type exhaust? Thanks for advice.

    Reply
    • Jason
      Apr 11 2016

      Daniel – I have no brand recommendation, only I’d look at Corsa for sure. They produce some pretty good Vette exhausts IMHO.

      As for what I would install, I’d stick with a cat-back to start. The SS uses the Corvette’s motor and exhaust manifold, which is carefully tuned. Unless you’re making some other changes – like adding a supercharger, cam changes, or some other intensive update – I’d leave the stock manifold alone. It’s as good as anything you’ll find on the aftermarket (probably better).

      Reply
      • Daniel
        Apr 12 2016

        @Jason, Thanks for advice, I have a Corsa coming soon and will hold off on a tune until I put in the supercharger(a bit later).

        Reply
  23. Matt
    May 6 2016

    Looking to add significant horsepower and torque to me 5.7 2015 dodge challenger. Where should I start and what brands are recommended?

    Reply
    • Jason
      May 9 2016

      Matt – No recommendations other than buying parts that come with dyno charts as proof of the promised gains. :)

      Reply

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