Byrd's Header?

[Jersey450R]

Whats up with the expansion chamber on his head pipe? Can someone tell me this. Is it the holeshot expansion chamber?! lol!

[GPracer2500]

I'm convinced it's a Helmholtz chamber. However, I've not heard an official description of it's purpose from DASA. If it IS a helmholtz chamber and it is reasonably effective, I look forward to seeing them trickle down into the exhaust systems we can purchase.

[400exrider707]

Originally posted by GPracer2500
I'm convinced it's a Helmholtz chamber. However, I've not heard an official description of it's purpose from DASA. If it IS a helmholtz chamber and it is reasonably effective, I look forward to seeing them trickle down into the exhaust systems we can purchase.

You posted this knowing full well that someone was going to ask you to explain what the heck a helmholtz chamber is and what it does... so get on with it!:blah:

Seriously I want to know...

[bwamos]

It's simlar to a 2-strokes expansion chamber, but the opposite in effect.

It will be tuned for a certian frequency (resonance). Aka, specific rpm. And in that RPM range it will resonate jsut right to help suck exhaust out faster on the next exhaust stroke, thus increasing flow while reducing the engines effort to expel the exhausts. Therefore giving you a little free HP at that RPM range.

Opposite of the 2-strokes pipe in effect because the 2-strokes pipe is designe to create a pressure wave back toward the engine. This would be designed to pull the exhaust away from the engine.

[Jersey450R]

Originally posted by bwamos
It's simlar to a 2-strokes expansion chamber, but the opposite in effect.

It will be tuned for a certian frequency (resonance). Aka, specific rpm. And in that RPM range it will resonate jsut right to help suck exhaust out faster on the next exhaust stroke, thus increasing flow while reducing the engines effort to expel the exhausts. Therefore giving you a little free HP at that RPM range.

Opposite of the 2-strokes pipe in effect because the 2-strokes pipe is designe to create a pressure wave back toward the engine. This would be designed to pull the exhaust away from the engine.

very good info!

[krt400ex]

is that the same header that was on kori ellis' bike? i think it was ellis...it was on a yammy though

[GPracer2500]

I think it's primary function is sound reduction. The use of helmholtz resonators to attenuate sound is a known strategy in some automotive exhaust designs. They cancel sound within certain frequencies--the specific frequency being dictated by the dimensions of the resonator. ETA (8/16/07): Devices called 1/4 wave tubes are sort of similar similar but I think what we're seeing is actually a helmholtz resonator.

Only recently have these chambers started turning up on racing ATV's and motorcycles (it's not just Byrd's bike--I've seen a few). I suspect the reason for this is the stiffening of sound output regulations. The AMA is at what, 99db right now? I believe the FIM is at 94db already.

I figure a helmholtz equipped exhaust helps a bike pass tech without having to make the compromises in flow that might otherwise be necessary. I asked DASA about it (online) but Dan declined to respond [shrug]. I've been wanting to learn more about Byrd's exhaust (or similar systems) for a while but haven't heard anything specific from anyone in a position to really know.

[JOEX]

Sounds interesting. With alot of focus on sound restrictions this could be the next 'big thing'...

Any pics or diagrams available?

[honda300EXtreme]

this helmholts chamber... would it be like the fmf megabomb or powerbomb header....?

to me it sounds similar because your using a chamber to lower noise levels and specifically increase your bottom end power

[300exguy125]

accually the mega bomb and power bomb will raise db's by a few from what they say

[GPracer2500]

http://www.atvriders.com/gallery/2007atvamx11unadillapromotoone/images/DSC_9463.jpg

http://www.atvriders.com/gallery/2007atvamx12lorettalynnproatvmototwo/images/KE2F1920.jpg

This one has a guard on it (don't burn your boots!).
http://www.atvriders.com/gallery/2007atvamx10sunsetridgepromotoone/images/KE2F6070.jpg

http://www.atvriders.com/gallery/2007atvamx10sunsetridgepromototwo/images/KE2F6448.jpg

http://www.atvriders.com/gallery/2007atvamx07ballancemotoxpromotoone/images/KE2F6683.jpg


Here's one on a KTM competing in FIM World Enduro.
http://img168.imageshack.us/img168/6007/ktmexhaust2is1.jpg

I've heard a variety of explanations for what these are and why they're there. My research leads me to believe they are helmholtz chambers used for sound reduction.

[GPracer2500]

Originally posted by honda300EXtreme
this helmholts chamber... would it be like the fmf megabomb or powerbomb header....?

to me it sounds similar because your using a chamber to lower noise levels and specifically increase your bottom end power

I don't think they're quite the same thing. They're similar in that they're suppose to manipulate exhaust gas and pressure but I don't think they "work" in precisely the same way.

FWIW, FMF does claim that the powerbomb and megabomb headers increase power and decrease sound. Personally, I'm skeptical about how FMF's headers work or what benefit they provide. I'm suspicious their design has more to do with distinguishing themselves in a crowded marketplace rather than actually working better than a "normal" header [shrug].

Those helmholtz equipped pipes on the other hand: there's plenty of well established science available regarding how they affect the acoustics of a system. Combine that with what Byrd's (and others') exhaust looks like and I'm compelled to believe we're looking at a helmholtz chamber used for sound control.

[honda300EXtreme]

Originally posted by 300exguy125
accually the mega bomb and power bomb will raise db's by a few from what they say

i dont know who told you that but thats incorrect,, im looking at an ad for the header as we speake

and i quote
" The FMF meganbomb Header Pipe Effectively reduces sound output by as much as 1.5 db."


but now after seeing a picture i realize what you guys are talking about and it definatly looks like an interesting concept, as GPracer said it would appear as its for sound reduction..

[bwamos]

Originally posted by GPracer2500
I figure a helmholtz equipped exhaust helps a bike pass tech without having to make the compromises in flow that might otherwise be necessary. I asked DASA about it (online) but Dan declined to respond [shrug]. I've been wanting to learn more about Byrd's exhaust (or similar systems) but haven't heard a peep.

Very true. I haven't seen Byrd's pipe. It very well could be tuned to reduce sound output at 3750 rpms (another function). But, IMHO it would be silly to overlook the performance advantages attainable from the technology.

Granted I havent run any calcs.. so who knows how large the chamber would be, or wouldn't be in order to captialize on the flow characteristics.

[INFAMOUSRACER7]

Originally posted by honda300EXtreme
i dont know who told you that but thats incorrect,, im looking at an ad for the header as we speake

and i quote
" The FMF meganbomb Header Pipe Effectively reduces sound output by as much as 1.5 db."


but now after seeing a picture i realize what you guys are talking about and it definatly looks like an interesting concept, as GPracer said it would appear as its for sound reduction..

Do you believe every ad you read?

[bwamos]

Originally posted by GPracer2500
I've heard a variety of explanations for what these are and why they're there. My research leads me to believe they are helmholtz chambers used for sound reduction.

After seeing the pics of exactly the setup's you are talking about, I would agree 100% that it is most definatly for sound reduction.

Those are setup like blowing across the top of a soda bottle. Makes a resonance to counter the engine's soundwaves.

[honda300EXtreme]

Originally posted by INFAMOUSRACER7
Do you believe every ad you read?


it has nothing to do with the ad, those are the facts,,, the header is proven to lower sound out put, thats all there is too it, and no i could careless what any ad says until i see the facts


thanks for the useless post though ;)

[krt400ex]

Originally posted by GPracer2500
http://www.atvriders.com/gallery/2007atvamx11unadillapromotoone/images/DSC_9463.jpg

http://www.atvriders.com/gallery/2007atvamx12lorettalynnproatvmototwo/images/KE2F1920.jpg

This one has a guard on it (don't burn your boots!).
http://www.atvriders.com/gallery/2007atvamx10sunsetridgepromotoone/images/KE2F6070.jpg

http://www.atvriders.com/gallery/2007atvamx10sunsetridgepromototwo/images/KE2F6448.jpg

http://www.atvriders.com/gallery/2007atvamx07ballancemotoxpromotoone/images/KE2F6683.jpg


Here's one on a KTM competing in FIM World Enduro.
http://img168.imageshack.us/img168/6007/ktmexhaust2is1.jpg

I've heard a variety of explanations for what these are and why they're there. My research leads me to believe they are helmholtz chambers used for sound reduction.


thats the yammy i was talkin about

[Toadz400]

Originally posted by honda300EXtreme
it has nothing to do with the ad, those are the facts,,, the header is proven to lower sound out put, thats all there is too it, and no i could careless what any ad says until i see the facts


thanks for the useless post though ;)

I've seen ads claiming Global Warming is real but I haven't seen any facts to back it up. ;)

This is pretty interesting, has anyone found any information anywhere else on these things?

[krt400ex]

Originally posted by Toadz400
I've seen ads claiming Global Warming is real but I haven't seen any facts to back it up. ;)

This is pretty interesting, has anyone found any information anywhere else on these things?


my ex drum teacher studied the whole global warming issue. he said that scientists base what they say on the fact that the earths core has warmed up a 1/2 degree in the last 100 yrs :rolleyes:


global warming my @$$

[REDRIDDER]

Global warming is real you guys ever watch the Discovery channel? ...lol....if it isn't they sure the hell fooled me hahaha...but back to the point of the exhaust every ones talking about, this is an interesting topic that i was unaware of until now never noticed...point is no one here works in the pits for a pro rider so we all can assume what its for until the facts are brought to use ...GPracer2500 you have 24hrs to find out the truth or.....i know you can do it...lol

[krt400ex]

Originally posted by REDRIDDER
...GPracer2500 you have 24hrs to find out the truth or.....i know you can do it...lol


lmfao :D

[biker56556]

dustin nelson has a similar chamber on his bike and he was saying that it was to reduce sound without sacrificing power Im shure thats what its for on byrds and browns bikes to .http://i44.photobucket.com/albums/f30/biker56556/KE2F63341.jpg http://i44.photobucket.com/albums/f30/biker56556/KE2F4195.jpg

[GPracer2500]

^ Good find.

That one kinda looks like a quarter wave tube instead of a helmholtz resonator [shrug]. Hard to see and I'm sort of guessing. AFAIK, quarter wave tubes and helmholtz resonators work in a little bit different way to achieve the same goal.

[GPracer2500]

Looks like these are starting to tickle down into systems available for purchase....These are Akrapovic systems.

For a 2008 CRF450R
http://www.akrapovic.net/uploads/pics/evolution.jpg


Here's a schematic of a 07/08 YZ450F dirt bike system:

http://www.akrapovic.net/typo3conf/ext/user_products/mod1/uploads/documents/9b566fbc59572ed3264114f1472f56c8.jpg


I haven't seen a production model for a quad.....yet.

[Hammer trx450r]

Its definatly for sound reduction

[tank69]

Looks like they found a use for all those Banshee Boost Bottles!

[flyin#5]

Originally posted by tank69
Looks like they found a use for all those Banshee Boost Bottles!


lol, exactly what i was thinking!


looks like they found a better way than clogging up the silencer to reduce noise which is a good thing. it'd be interesting to see a dyno to see how it affects your hp.