Will Helmholtz resonator decrease power?
 

Hi guys,

I see a few test pipes come with a Helmholtz resonator, for example the Nameless front pipe and the ARK front pipe. I tried to search about Helmholtz resonators but not much was found.

Basically my question is:

Comparing HFC with Helmholtz resonator, which one sucks away more power?

Which one is louder?

I hope vendors with better knowledge can also comment on this question.

Thanks

I wouldn't have thought the removal of certain sound waves would reduce power? Even the slight effect to the flow past the outlet would seem insignificant compared to the friction through the muffler's perforated tubes?
Might even increase power a tiny bit?
Dunno!

Nope, they dont suck power. =)

Doesn't suck power away.

With Helmholtz resonator it's quieter, that's their purpose.

Do we have any dyno comparison to prove the helmholtz do/dont decrease power?

I haven't seen a Dyno but it's just a matter of design. A Helmholtz is not impeding flow in any way. It's something similar to the car's sound tube, just particular sound waves going into it, not much more.

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Reason I asked is I'm thinking of running a helmhotz resonated catless front pipe.

Not to threadjack, but it is slightly related - does anybody know which limits noise more... A Helmholtz resonator or regular resonator (perforated tubing wider than the normal piping)?

Helmholtz are tuned to cancel/significantly reduce specific frequencies. Not the entire range. So they can cancel drone at low rpm/cruise, but keep high rpm WOT loud.

Normal tube resonators basically act as mufflers, lowering all frequencies a bit, and a target range a little bit more.

Oh cool - I have a resonated (perforated tubing, not helmholtz) catless frontpipe so probably better to affect the entire rev range once I get a header.

Helmholtz will not decrease power in any way. This is used for soundwaves not for the flow of gas.

Here is a better explanation of a Helmholtz resonator:

It can be shown[2] that the resonant angular frequency is given by:

http://upload.wikimedia.org/math/7/7...9a85057abb.png radian/s), where:

• <LI sizset="false" sizcache04063859185909552="43 116 21">http://upload.wikimedia.org/math/3/3...b65ee1b103.png (gamma) is the [ame="http://en.wikipedia.org/wiki/Adiabatic_index"]Heat capacity ratio - Wikipedia, the free encyclopedia[/ame] capacity ratio or ratio of specific heats. This value is usually 1.4 for air and [ame="http://en.wikipedia.org/wiki/Diatomic"]Diatomic molecule - Wikipedia, the free encyclopedia[/ame] molecule is the cross-sectional area of the neck
• http://upload.wikimedia.org/math/6/f...88d9a1501b.png is the mass in the neck
• P0 is the static pressure in the cavity
• V0 is the static volume of the cavity

For cylindrical or rectangular necks, we have

http://upload.wikimedia.org/math/b/3...a8531e9eb6.png , where:

• L is the length of the neck
• http://upload.wikimedia.org/math/2/8...16cf091955.png is the volume of air in the neck

thus:
http://upload.wikimedia.org/math/8/a...645186088a.png By the definition of [ame="http://en.wikipedia.org/wiki/Density"]Density - Wikipedia, the free encyclopedia[/ame]: http://upload.wikimedia.org/math/b/d...f5c147b62d.png, thus:
http://upload.wikimedia.org/math/7/9...91dac6f1d4.png , and

http://upload.wikimedia.org/math/4/f...788ee2ce00.png , where:

• fH is the resonant [ame="http://en.wikipedia.org/wiki/Frequency"]Frequency - Wikipedia, the free encyclopedia[/ame] Hertz The speed of sound in a gas is given by:

http://upload.wikimedia.org/math/8/c...d3bc6bb996.png , thus, the frequency of the resonance is:
http://upload.wikimedia.org/math/8/2...30067ccbff.png The length of the neck appears in the denominator because the inertia of the air in the neck is proportional to the length. The volume of the cavity appears in the denominator because the [ame="http://en.wikipedia.org/wiki/Spring_constant"]Hooke's law - Wikipedia, the free encyclopedia[/ame] law of the air in the cavity is inversely proportional to its volume. The area of the neck matters for two reasons. Increasing the area of the neck increases the inertia of the air proportionately, but also decreases the velocity at which the air rushes in and out.
Depending on the exact shape of the hole, the relative thickness of the sheet with respect to the size of the hole and the size of the cavity, this formula can have limitations. More sophisticated formula can still be derived analytically, with similar physical explanations (although some differences matter). See for example the book by F. Mechels.[3] Furthermore, if the mean flow over the resonator is high (typically with a Mach number above 0.3), some corrections must be applied.


Anyone else here watch Big Bang Theory??

I'm going to look into the Helmoltz too if I get a catless header & exhaust.. but those equations look like jibberish to me.. just tell me how many decibels does it drecrease the noise level at 3500 rpm WOT? :D

Also something else that I came across.. VaraFlow Muffler! It'd be great if you could adjust the sound of your own exhaust! But I don't know of anyone who's tried this product before..

http://i965.photobucket.com/albums/a...ps0a84db82.jpg

You don't have to keep it so simplistic.
I'm sure we can manage to follow a more in depth explanation.:eyebulge: