Exhaust Diameter, Length, and Baffle

How about the differences in exhaust as related to exhaust diameter, length and baffle? Most of us are looking for the deepest sound we can find and rely on websites for sound bytes, which you know never sound like the real thing. If we could understand how size effects sound, we can make a better informed decision on the pipes we buy. P.S. we also still what performance.

Our Friends at SuperTrapp had this to say:

If we’re talking about straight through pipes with no mufflers/baffles then a smaller diameter pipe will give you a snappier sound (high frequency) and a larger diameter pipe will give you a deeper sound (low frequency). Longer pipe lengths lessen the volume of sound and shorter pipes increase the volume of sound. Something to keep in mind is that the human ear is more sensitive to higher frequencies; this means that we perceive these sounds as louder. If a muffler or baffle is added to the equation then the pipe size has only a minor affect on the overall sound. Also, a muffler can alter sound significantly depending on the design. Many technologies are employed in the design of mufflers or baffles. At this point we need to understand the difference between a muffler and a baffle. A muffler is a mechanical assembly that employs multiple components and technologies to reduce sound in an exhaust system. A baffle is a mechanical device used to disrupt sound waves. In most cases baffles are used as a component in a muffler assembly. The term “Baffle” has become common these days because of their use in drag pipes. They’re used in drag pipe designs due to the limited space inside of the pipe. Muffler assemblies are far more complex. These assemblies can incorporate many components to alter sound waves. These components can range from packing materials such as fiberglass, ceramic wool, and stainless wools to perforated tubing, baffle tubes, and baffle plates or any combination of these components. Due to the vast design configurations and their abilities to manipulate sound, there is no hard fast rule that can be given to say how a specific muffler will sound. Unfortunately, as we’ve learned, “you cannot muffle horsepower”. All street exhaust designs are a balance between power and appropriate sound quality. Something else to keep in mind is that the engine configuration plays the biggest part in overall sound. Compression ratios, cylinder heads, cams, and ignition timing all affect the sound output of any given engine.

Wrench Safe, FMH
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33 Responses to “Exhaust Diameter, Length, and Baffle”
  1. rick roden

    I have a 1981 cb900c with pods; the airbox was broken.
    the headers are 4 into 2, with cylinders 1 & 4 going to the right, 2 & 3 going to the left.
    the tail ends of the headers are 2″ OD.
    there is no cross ventilation pipe and the holes where it was have been welded over.
    the slip ons I had on there were rusted beyond practicality, and I purchased some EMGO dunstall replicas with the reverse cone on the end, +/- 27″.
    the ID of the muffler, where it slips on to the header is 1.5″. 2 reducers are included.
    my question is: is this dimension of the muffler going to be workable with my engine? I can have an adapter made but I’d like to know that this won’t create too much back pressure in my system. thanks for taking my question- rick

    • Customer Service

      Hi, Rick. Sorry. That question is better for Honda engineering. We just turn wrenches.

  2. Daniel

    Installed Vance and Hines power duals , kept the Screaming Eagle mufflers and had it tuned. If I change the mufflers , will I need to tune it again.My bike is a 2014 Streetglide with a 110 stage 4 kit .

    • Customer Service

      Hi, Perry. We would be happy to assist you; we just need some more information. What is the make/model/year of your motorcycle?

      • Rick milam

        I have a 2015 harley roadglide that I have had converted to a trike.i have v&h power duals with super trappe mufflers dutt to fitment issues with trike kit.it had 4.5 VHS high output mufflers before trike conversion. Will I need to retune now..

        • Customer Service

          Hi Rick!

          That’s a great question!

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  3. Mike Bender

    Interesting article. I personally do not like the sound of shorty pipes, they are too much noise with too little quality.

    Even with long pipes such as Vance and Hines long shots I suppose the diameter could still affect sound quality. I bought some since I loved the way they sounded on other bikes but after a whole season of riding I realized they had the perfect frequency to make my ears ring after riding for a couple hours.
    When I replaced the factory pipes I realized they had a lot more low end torque and that was when I learned it was due to the cross over pipe. I don’t know if the cross over affects sound, but it sure as dickens affects my ability to make a smooth launch when I’m loaded down. I’ll never install pipes that do not have a crossover. Might want to share that with your readers.

    • Peter Fox

      I have Vance & Hines Long Shots with no cross overs on my HD 2006 Fat Boy EFI FLSTFI and the sharp crackle in the ears isn’t great on long runs of an hour or more. Doesn’t have oxygen sensors but my local Harley shop convinced me to have fitted a Screamin Eagle Super Tuner fitted so i did. Can’t say I’ve noticed much difference (maybe on a Dyno). Can I do better? I would like to reduce the sharpness in sound without losing the pipes altogether and performance as well.

  4. Donny oehlecker

    I have a ’14 superglide custom. Im wanting to change from my stock mufflers. My stock mufflers have the catalytic converter inside the mufflers. If i go aftermarket will i have to have it mapped?

  5. Ronnie

    I have a new 2017 flhtkl limited low w/107. I had the dealer install Cobra 4″ race pro slip ons. I prefer a little louder sound. Is there anything I can do with the baffle to increase sound. I dont want to remove the baffle entirely. Can i remove baffle and drill out larger holes, etc.?

    • Customer Service

      Hi Ronnie. I would not recommend altering those baffles in any way. Drilling larger holes may not necessarily give you the sound you are looking for.
      Best to determine what exhaust/muffler sound you prefer and install that. Try to sell the Cobra mufflers and recoup your money already spent. I am sure you will not have any trouble unloading those.

    • Guy Ramsden

      maybe you can just take out the packing that goes around the baffel. then put the baffel back in!!

  6. Anthony

    I have a softail EFi with screaming eagles i hate the sound, no low frequency…
    removed them and an amazing sound with great lows but way to loud!
    what would you advice to get that low sound with less DB.
    they are 51mm

  7. Bill K

    I have a set of Hi Lo V&H straightshots on my fxsts springer. I want to put some fishtails on the ends but Vance and Hines uses that 2 1/8 output. I cant find any tips that fit. I was wondering whether the head pipe is 1 3/4 so I can just get some slipon fishtails and just do a custom mount bracket? any ideas ? Thanks for taking my question -Bill

  8. sang truong

    Hi i have a D&D bob cat 2:1 exhaust system for my 2008 sportster. I am looking for a new baffle for the exhaust system because i bought the bike without one. The exhaust system is discontinued. ANy idea which type of baffle i can use for an alternative. the diameter is 2 3/4 inch but i dont know the length. How do i find out.

  9. John

    I have an 06 flstc with a stage 2 screaming eagle air kit and I’m going to be putting on a screaming eagle 2 slip on mufflers with either no baffles or a loud baffle like big city thunder monster baffles. I have not had remap and im wondering what type of fuel controller to get. There are no 02 sensors on this bike.

  10. Mike smith

    I want to put baffles in my shorty drag pipes on my 78 shovelhead, I have a set of 4″ and 6″ baffles. Does the length matter when it comes to the loudness? I just want to quiet it down a little as they are way too loud

  11. Sal

    What’s the inner diameter on the tip of the exhaust header pipe of 2012 Fatboy Lo? Need to know to remove the baffles that are inside the slip-ons and add baffles on header instead.

  12. Kurt Halliwell

    I have an ’82 fxs low rider with 2″ drag pipes that I inherited from my brother. It is a little loud, harsh for my liking. I am not sure of the make of the current exhaust, but would the vance and hines baffles work, or are they specific to the V&H products? Thanks

  13. William Stone

    A late friend of mine had a new set of Samson shotgun style exhaust system put on his ’92 Harley Softail with a 1340 EVO engine and this exhaust came back to about the rear axle point on his bike. He told me that he had torque cones installed and the baffles removed and it sounded awesome. It had a deep low hotrod tone without the hollow open pipe sound that you often times hear with open pipes. It also had a ton of reversion when you let off of the throttle between shifts that I thought gave it that hotrod sound. I’ve heard that torque cones are a marketing gimmick and that they do nothing for performance but I’m wondering if it at least helps with the sound on an exhaust without any baffles? Even the ’06 Dyna Wide Glide I had in ’08 had shotgun exhaust(not sure what brand, couldn’t find a name on them) without baffles and it still had a slight hollow open pipe sound. His sounded much better and I’m not sure why, I’m wondering if it was the torque cones. Anyway, I’m picking up my new to me ’05 Dyna Wide Glide EFI with Vance & Hines Longshots and I’m hoping to be able to closely duplicate the sound of my late friends bike. I don’t think it’ll have the same reversion because these fuel injected engines don’t fall off like a carbureted engine does between shifts. The rpm’s seem to drop more gradually than carb models thus eliminating some of the reversion but we’ll see how it goes.

  14. Chema

    Ticket 23117 I just bought a 2014 sporster XXL that had the pipes edge cut off and drilled holes in the muffler, sounds great but I’m looking to repair the whole sistem since the bike is heating too much and loosing performance, what would be the best diy solution to this?

  15. Dick Fiscus

    question for the pros-I just bought an ’01 Heritage softail classic (not EFI) with Vance & Hines longshot exhaust (ID 2-1/4″)..the bike positively roars..I’d really like to quiet it down drastically…seen good review of V&H Super Q baffles but can find their dimensions…can you tell me what the quietest baffle set-up would be for this bike? Got a lot of Senior neighbors and would rather not destroy their “Miracle Ears”

  16. Joe

    2012 fatboy low, how to remove the baffles to make it louder and what effect will it have on the bike

    • Customer Service

      Dear Joe,

      Thank you for your patience. In response to your question-

      The factory baffles are not meant to be removed. Attempting to do so will only be damaging to the muffler.
      We suggest looking into Vance and Hines or Supertrapp exhaust systems.

      We’d love to have you be a part of our community. We are convinced you will enjoy the benefits of becoming a member and having access to the best instructional how to videos and professional tips. We would like to offer you a special promotion for your first-year membership.

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