Helmoltz resonator for drone

[madkaw]

Anyone try this ? With all my mufflers and resonators I am still dissatisfied with my drone at low rpm loads. I'm about done trying any other mufflers so I'm going to try this type resonator . It might be a matter of where it will fit as far as location . I might actually be able to get rid of my muffler - resonators and loose some weight going this style . The pic is just a general idea but I've read that just a length of pipe will do , sounds like around 24" piece does the trick. It can be basically attached at a 90 degree angle to the pipe, but after that it can be bent to fit anywhere .

[Chickenman]

I'm running a 2.5" system with an oval Magnaflow Muffler  ( #11246 ) for a resonator and some sort of un known " Turbo " Muffler at the back. No drone what so ever. Reasonable noise levels, but a nice 6 cylinder wail when you get on it. The Magna Flow oval muffler as a resonator really cut the drone and over all noise down. Straight through so really no restriction. 

https://www.magnaflow.com/products?partNumber=11246

 

 

Hmmm... you need to change your signature 

Edited July 28, 2017 by Chickenman

[madkaw]

I have twice the issue with twice pipes . I run oval in the back with round resonators up front , combined with headers . I thought I could ditch the round resonators for something like this type resonator .

[Chickenman]

Twice pipes can be  harder to control noise with than a single...   Round resonators really don't cut back noise or drone much. Too small of and over all diameter. You need an oval resonator to allow the gases more room to expand and dissipate their energy. 

Magna Flow does make some Dual I/ Dual out Oval Mufflers. What size are your twice pipes?

 

 

[Chickenman]

You could also add an H pipe between your Twice pipes. That will cut down on resonance as well. Done on V8 systems and really helps.  H pipes do have an ideal location for placement. You want it at a high velocity area, before it starts losing all of it's energy. 

Use some cheap, non-heat resistant Black paint and paint a Stripe on the bottom of the exhaust pipes. Now go make some WOT runs on the Freeway. The paint will burn off in the high velocity areas .  Put your H pipe or Helmoltz resonator in that area. 

[madkaw]

What I read on some other sites was that the resonator pipe ideal length was 24-26" per pipe, so 1 H pipe would need to be 5 ft . 

I do have a crossover in there now, but that was meant for scavenging , and I would gladly do away with it for a bit more civility at lower rpms

[wheee!]

Resonators work great. I have them on my HKS exhaust on the 370Z.
No drone and awesome sound.

[Zed Head]

Have you tried the factory pre-muffler?  It's true name/purpose might have been lost in translation.  Seems like we should be using the word anti-resonance, or resonance-damper also.  Resonance is what causes the drone, I believe.  "Glass packs" are the typical substitute for the pre-muffler.

Doesn't the 370Z have catalytic converters?  Kind of confounds the cause-effect equation..

[madkaw]

I have glass packs ( resonators ) ahead of oval mufflers . The glasspacks help a little but as they break in they are less effective. 

Yes Mark- that's what I'm taking about. 

Richard - I'm running twin 2" pipes. Packaging is the issue . There's no room for ovals where the glasspacks are in the tunnel. There would be room for a T'd pipe. Most projects I've seen the pipes are very close to the mufflers so I don't know if they would be as effective further upstream . If not I might be able to package things differently 

[wheee!]

Have you tried the factory pre-muffler?  It's true name/purpose might have been lost in translation.  Seems like we should be using the word anti-resonance, or resonance-damper also.  Resonance is what causes the drone, I believe.  "Glass packs" are the typical substitute for the pre-muffler.
Doesn't the 370Z have catalytic converters?  Kind of confounds the cause-effect equation..

370's have cats but I replaced mine with hi flow Berk cats. Sound is perfect, restriction is minimal.

[Zed Head]

 

3 hours ago, wheee! said:

Resonators work great. I have them on my HKS exhaust on the 370Z.
No drone and awesome sound.

My more direct question should have been "does it drone without the (anti-)resonators?  Serious question, just wondering.

Could be that the pre-muffler (anti-resonance muffler) works best with six exhaust pulses, but not with three.  Just trying to distinguish why they work for some but not for madkaw.

[wheee!]

Helmholz resonators require an accurate diameter and length to "trap" the offending frequency.
If you compare the HKS exhaust to the Fast Intentions brand, the only difference is the resonators really. The FI exhaust has horrible drone.....