What's that stub on Knights exhaust? - Page 2

Simon · May 1st, 2007, 02:56 AM

Hey chaps,

What you are looking at there are branch resonant chambers. As you'll notice there is a small cross-section bit of pipe connecting the exhaust system to the canister.

They do not work in the same way as the FMF power bomb which is a change in cross-sectional area of the exhaust pipe. Even the acoustic properties and effects of each in the pipe are different - but conversely they may be there to assist in achieving a similar objective.

The branch resonator will be there to reduce the pressure wave of certain sound frequencies so they could be to reduce overall exhaust noise or to reduce the sound pressure pulses back to the cylinder to increase performance or to stop a reduction of performance at certain engine speeds (in reality it will work in both directions). The specific design purpose depends on a number of other factors, including, most notably camshaft design.

The branch resonator does not function as an expansion chamber.

Acoustically the resonant chamber will only function well over a very narrow frequency range so it is a very specific issue that they're trying to target. On the other hand, it may be just a gimmic that doesn't cost anything to get people talking

Hope this helps.
Simon

Gokai134 · May 1st, 2007, 05:58 AM

hi Simon,

so by counting 1&1 together:
that means the KTM-Factoryriders are using an loud /free flow exhaust to gain a maximum of performance -
but at soundtesting their bikes stay within the legal "sound emission" ...
so, isnÂ´t this

???

Anyway, thanks for your brief explaination

Smorgasbord · May 1st, 2007, 11:53 AM

Ha! I think you hit the nail Gokai134! The dB testing is done at a specific rpm. Just tune in the stub to that rpm and your illegal pipe will pass the test! Any other rpm than the test rpm and it will sound like shite! That is really really the way you describe it with the little animated illustration. Shame on you KTM!, if this is the case. Cheating is cheating no matterhofen how you turn it. They grab any straw now (?) to not get beaten by the Bergs... In some cases to no avail, as it went.

And thanks for the explanations.

I bet KTM would like to mark out the stroke on their cylinders so that no one uses a slightly wrong rpm at the dB test, that would spell disaster!

Besides these conspiracy theories, I'd still like to see a picture of the stub, if there is any. Maybe it's still just a way to dampen offensive frequencies from the legal silencer, if that is the case then it is most welcome and a good initiative.

Regards.

Goran · October 9th, 2007, 01:34 AM

I discovered this topic late, but was also curious about this thingies on exhausts.

As usual, here are the pictures (taken on WM MX3 and EM MX2 in Jaska, Croatia, this summer).

Can we expect such a pipes (and two level seats, too !!) on production bikes (hint -

09)

Cheers, Goran

Goran · October 9th, 2007, 01:36 AM

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Goran · October 9th, 2007, 01:39 AM

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Goran · October 9th, 2007, 01:41 AM

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Goran · October 9th, 2007, 01:44 AM

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Goran · October 9th, 2007, 01:46 AM

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Goran · October 9th, 2007, 02:01 AM

... pictures ...

..26 - KTM Akrapovic
..33 - KTM
..34 - KTM
..37 - KTM Higashi
..38 - Honda
..42 - Yamaha
..46 - Yamaha Higashi
..50 - Honda
..51 - KTM SXS 505 Akrapovic
..52 - KTM Higashi
..55 - Breugelmans KTM
..56 - Breugelmans KTM detail
..57 - Breugelmans KTM detail
..58 - Breugelmans KTM detail
..60 - DeMaria`s Yamaha
..61 - DeMaria`s Yamaha - carbon tank!!
..66 - Honda Akrapovic
..67 - Honda Akrapovic

... and bunch of other pictures somewhere on my hd.

Enjoy all