Fixing exhaust drone with resonator tube (aka j tube/j pipe): how to calculate tube

[mindgame100]

Hi,

I just purchased a used GEN 1 Raptor today, and this puppy has the worst droning issue I have ever experienced.

I came across this in another forum, in hopes of finding a way to eliminate the droning at a certain or various RPMs..

https://www.reddit.com/r/FocusST/comments/2bhxza/fixing_exhaust_drone_with_resonator_tube_aka_j/

Has anyone tried this?

Thanks!!

 

[ARH1956]

Many folks here have built/used this with great success. I used a 2.5" x 26" pipe on mine and it completely eliminated the drone on my system. I live in a mid-sized town, about 65K in pop., in NE Alabama and the shops here had no clue about a Helmholtz Resonator. I did the research online, determined the tube size and length needed and drew a picture for the muffler shop. I took it to the muffler shop and the guy said he couldn't imagine how it would help but built exactly what I asked for and it's perfect. Volume unchanged as far as i can tell and the drone is completely resolved. My exhaust was a muffler change only, to a Borla 40349, which introduced a little drone. http://www.fordraptorforum.com/f160/helmholtz-resonator-no-more-drone-40125/

 

[NE Ford]

@t_j

 

[t_j]

Didn't do the math on it but used the fairly commonly quoted length there and works pretty well the ones I have installed are ~24" when measured around the outside of the bend in them total length is ~20". There seems to be a small amount of give in the length calculation so don't worry if its not perfect.

 

[Canuck714]

I made a 26 inch 2.5 diameter j-pipe to take the drone out of my 14 Roush. Works great, and makes driving in the 16-1900 rpm range way better. When you stand on it, all the wonderful noise is still there.
Had mind made at a muffler shop for $65.00 installed

 

[HORN HIGH ACES]

Many folks here have built/used this with great success. I used a 2.5" x 26" pipe on mine and it completely eliminated the drone on my system. I live in a mid-sized town, about 65K in pop., in NE Alabama and the shops here had no clue about a Helmholtz Resonator. I did the research online, determined the tube size and length needed and drew a picture for the muffler shop. I took it to the muffler shop and the guy said he couldn't imagine how it would help but built exactly what I asked for and it's perfect. Volume unchanged as far as i can tell and the drone is completely resolved. My exhaust was a muffler change only, to a Borla 40349, which introduced a little drone. http://www.fordraptorforum.com/f160/helmholtz-resonator-no-more-drone-40125/

Any chance you could provide a picture of your set up or provide a copy of the diagram you provided your muffler shop?

 

[ARH1956]

Any chance you could provide a picture of your set up or provide a copy of the diagram you provided your muffler shop?

Yes, I'll try to get one tomorrow.

 

[ARH1956]

Yes, I'll try to get one tomorrow.

Work stuff prevented a picture today, out of town Friday. It'll be Saturday before I get the picture.

 

[Chinmasterflex]

I actually added a a hemholtz resonator onto my MBRP turndown exhaust (with resonator) last week. Originally we used a 3" x 29" pipe but found it to be too long and was effective at too high of an RPM or be useful below 75mph and made the exhaust overly quiet overall. After incrementally shortening the length, i also found that 26" was decent for my setup as well for 60-75mph (TX highway speeds) but an inch or two shorter would probably be ideal.
I definitely agree that anywhere in the 24-26 range will probably get you where you need to go.

 

[ARH1956]

http://www.fordraptorforum.com/atta...lmholtz-resonator-no-more-drone-helmholtz.jpg
Not mine but the same thing