Exhausts Glossary

Want to know the differences between our Shorty and Flanker muffler? Or confused about whether you need to tune your bike after installing a Kelpi system? (spoiler alert: the answer is "no") Below, we've put together an in-depth rundown of our most commonly-asked questions about our exhaust systems below. Be sure to scroll to the end of the page for a quick video explainer of our baffles, how to use them, and tips for installing them.

Do I need a tune?

We've plotted every muffler and baffle combination against the OEM muffler on the same bike (the centre of the chart). Left to right shows fuelling: rich means more fuel for the air going in, lean means less. Bottom to top shows power. Every option lands inside the green safe zone, so a tune isn't needed for any of them.

More power Less power Richer Leaner OEM 1 2 3 4 5 6 7 8 9

Orange circles are Flanker options and teal diamonds are Shorty options. Numbers match the list below.

  • Safe zone The green circle: no tune required for any option inside it.
  • 1Flanker No baffles
  • 2Shorty No baffles
  • 3Flanker Standard tube-type baffle
  • 4Shorty Standard inlet baffle only
  • 5Flanker Quietcore baffle
  • 6Shorty Outlet baffle only
  • 7Shorty Quietcore inlet baffle only
  • 8Shorty Standard inlet + outlet baffles
  • 9Shorty Quietcore inlet + outlet baffles

Please note: positions are our own relative ratings compared with the OEM muffler on the same bike, shown as an indicative guide rather than measured results. Exact changes vary with the bike's make, model and year, the engine type and size, the airbox and any other modifications.

Muffler loudness scale

Every Flanker and Shorty baffle combination, rated from 1 (quietest) to 10 (loudest).

  • Flanker Raspy, higher pitch, aggressive in the upper rev range.
  • Shorty Rumbly, bass-heavy, aggressive in the lower rev range.
  • OEM A typical stock muffler, shown as a reference point.
  1. FlankerNo baffles
    10
  2. ShortyNo baffles
    9.5
  3. FlankerStandard tube-type baffle
    8.5
  4. ShortyStandard inlet baffle only
    8
  5. FlankerQuietcore baffle
    7.5
  6. ShortyOutlet baffle only
    7
  7. ShortyQuietcore inlet baffle only
    6.5
  8. ShortyStandard inlet + outlet baffles
    6
  9. OEM mufflerStock reference point
    5
  10. ShortyQuietcore inlet + outlet baffles
    4

Please note: actual dB readings aren't shown here because the volume of our mufflers depends on the bike's make, model and year, the engine type and size, and the testing conditions (e.g. idle, free-rev or ride-by). This scale is consistent across those different testing conditions, so it can be used to compare the perceived loudness of our different muffler and baffle options. It is a relative 1 to 10 rating, not a decibel scale.

Why decibels don't tell the whole story

Decibels (dB) measure how much sound there is, and every +10 dB sounds roughly twice as loud to us. But our ears aren't equally good at hearing every pitch. They're most sensitive to sharp, mid-to-high sounds (around 2,000 to 5,000 Hz, where speech and warning sounds live) and much less sensitive to deep bass. So a raspy, higher-pitched exhaust note can sound louder than a deep rumble, even when the bassy one has the bigger dB reading. That's why we rate our mufflers by how loud they sound to a rider, not just by what a meter says.

Sounds loudest to our ears about 2,000 to 5,000 Hz Rumble Rasp Ear sensitivity (higher = louder to us) 20 100 1k 10k Pitch in Hz (low to high)
  • Rumble The deeper, bass-heavy character of our Shorty.
  • Rasp The sharper, higher-pitched character of our Flanker.
  • Overlap The two sound much alike. Both sit mostly where our ears are most sensitive, with the Shorty leaning a little deeper.

Watch our Baffle Rundown Here

If you're still confused about how to install a baffle into one of our mufflers, or want to see the difference between an end-cap baffle (Shorty only) and an inlet baffle, then check out our quick video explainer below.