Need help with Drone

[M3Convert]

M3C,
You mentioned "a video to come". Do you have one to post?

Did your 13" Helmholtz tube cancel the full 1,000 rpm drone range? I've heard it only cancels about a 400 rpm range. UNfortunately, my drone is from 1400 to 1900 rpm (1750 peak), so I'd need a 37" Helm. res. tube. :eyebulge:

Any idea which ( inline resonators, x pipe, Helm. res tube) mod did the most to stop drone? Helm. I'm guessing.

I "meant" to get a video...

If you look at the tube, it is stepped, so the volume inside increases, which will affect the sound (cf snare drum vs bass drum), effectively shortnening the tube...in my picture, it has gone from a "calculated" 36" tube, to an 18+" tube. The tube can also be doubled back if you go with a straight tube. The resonator tube can be tuned by sliding the pipe to different lengths on the Helmholtz pipe, like a trombone, to get the desired supression point. This means different diameter pipe can be used to achieve the same goal. Once you have the right supression, the tube is welded at that position, so you don't have to guess and commit. This will take a little shop time, but you will get a truly custom exhaust note!

What happens is the drone is suppressed to a much quieter level, similar to the background of an aftermarket exhaust, rather than totally eliminating it. The response is analog, not digital, so the supression builds and wanes gradually, so a range of drone is supressed, rather than just on/off at one frequency

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[davekro]

I "meant" to get a video...

If you look at the tube, it is stepped, so the volume inside increases, which will affect the sound (cf snare drum vs bass drum), effectively shortnening the tube...in my picture, it has gone from a "calculated" 36" tube, to an 18+" tube. The tube can also be doubled back if you go with a straight tube. The resonator tube can be tuned by sliding the pipe to different lengths on the Helmholtz pipe, like a trombone, to get the desired supression point. This means different diameter pipe can be used to achieve the same goal. Once you have the right supression, the tube is welded at that position, so you don't have to guess and commit.

What happens is the drone is suppressed to a much quieter level, similar to the background of an aftermarket exhaust, rather than totally eliminating it. The response is analog, not digital, so the supression builds and wanes gradually, so a range of drone is supressed, rather than just on/off at one frequency

Do you recall the company you got the expanding diameter Helm tube from? First I've heard of this twist to a Helm. res tube. Previously I understood that using a larger dia. pipe suppressed a slightly wider rpm range. I think a 400 rpm range was for a ≈2" pipe. So I was... how can I do 3" pipe 37" long! :eyebulge: ;)

 

[M3Convert]

Do you recall the company you got the expanding diameter Helm tube from? First I've heard of this twist to a Helm. res tube. Previously I understood that using a larger dia. pipe suppressed a slightly wider rpm range. I think a 400 rpm range was for a ≈2" pipe. So I was... how can I do 3" pipe 37" long! :eyebulge: ;)

It was a custom build. It is regular exhaust piping of different diameters stepped up. I think the end pice started life as a cherry bomb muffler. My buddy who runs the shop also builds exhausts for race cars, so he was interested in the challenge of building this, and used to putting custom exhausts together. That being said, it wasn't rocket science and the sliding pipe adjustment to tune the exhaust helps avoid wasted time and materials.

 

[Rv-Junke]

Try this company / link:

http://synapseengineering.pinnaclecart.com/index.php?p=catalog&parent=23&pg=1

 

[robb]

On friday I had a local muffler shop weld on two Magnaflow 10416 mufflers with 4 inch tips similar to another user on here. I also have the resonator H pipe delete kit. Exhaust sounds amazing, but when I hit fifth gear at 40 mph and especially 6th gear at 50-75 the noise in the cabin is unbearable. I think it's drone, I've never had a car with an upgraded exhaust before so I'm assuming it is what's called drone, it's head splitting. I put the stock resonator back on (luckily it lined up with the H pipe section) and it helped a bit, but at 50-60 it's still pretty bad. A buddy of mine who has 3 fox body mustangs told me I would have to go from the round mufflers to the oval, which i looked up and Magnaflow 11226 would be the direct fit. But I would lose that great rumble on the outside.

What I'm confused is all the reviews I read on these 10416 mufflers stated no drone, quiet on the inside at cruising, and so on. So why so bad on my mustang? Is it the 3.31 gearing? And before I go blowing another $400 between the two mufflers and the install at the shop (that I really really don't have) is there anything I can do?

I already put the stock resonator back in. I have my JLT CAI intake coming in soon, which I believe comes with the sound tube delete, will that help (getting rid of the sound tube that is). I also read on a forum after a google search for these mufflers that someone put some sound deadening material in the trunk to help it. I would like to go back to my H pipe, and I love the rumble on the outside, but as I do a lot of highway driving as it is now it is just unacceptable.

Also another user mentioned that after a bit the 10416 mufflers should smooth out a bit, I guess as the material inside packs in or settle, will this help? Any suggestions would be great.

I'm extra sensitive to drone so even the FRPP Touring catback gave me a headache and it's a fairly mild aftermarket system. Maybe you're like me and just sensitive to it.

 

[davekro]

I'm extra sensitive to drone so even the FRPP Touring catback gave me a headache and it's a fairly mild aftermarket system. Maybe you're like me and just sensitive to it.

Robb,
did you have the above system on your car? What did you do or change to to get rid of your drone? I'll describe fully on the exhaust sound clip thread on my changes... but basically I cut my welded on Magnaflow 11366's (were supposed to be 2 1/4" 11365's !!!) off and was only able to slide them forward 1 5/8". This allowed enough length at the back end to go to 9" tips. I've tried a few brands of 9" resonator tips. The drone 'seems' somewhat less loud, but still more than I think I really want to live with.

I'll hold with this until Blaster with another convertible installs the same parts as mine (except he really got 11365 2 1/4" ers!!!) and see what he gets. Also waiting for Blaster to install his BBK shorty headers to his Roush exhaust with drone to see his outcome.

 

[Varekai]

I'm extra sensitive to drone so even the FRPP Touring catback gave me a headache and it's a fairly mild aftermarket system. Maybe you're like me and just sensitive to it.

I believe I am sensitive to it because it doesn't seem to bother my fiance as much. But the drone is very strong, like I mentioned in an earlier post the resonance or reverb of the drone is so bad it actually rattle's stuff in the cab, like stuff I keep in the door storage areas, glove box and you can feel it in the wheel and shifter.

 

[Varekai]

Helmholtz

I had a Magnaflow on my M3 and it was God-awful at ~2000 - 3000 RPM. I did this mod:
http://www.m3post.com/forums/showthread.php?t=754740&highlight=helmholtz

and it made a world of difference. A good exhaust shop can get the length just about right, and you get all the noise when you want it at high RPM, without the drone at cruising.

http://www.minihausperformance.com/archives/734

So exactly how did you find out the frequency of your drone in your thread? I saw RV figured out his frequency/hz as well. Is there a tool for this?

 

[murphyslaww]

I have the MF comp on my Base as well.

I think we may be getting more with the 3.31 and where we tend to be at highway speeds.

Mine, as some have said, seems to have quieted down some now that there is 3000 miles on it or so.

 

[Rv-Junke]

So exactly how did you find out the frequency of your drone in your thread? I saw RV figured out his frequency/hz as well. Is there a tool for this?

There is a formula, I'll send you the Excel file. I also, download a BUNCH of wave files with various HZ., Ill see if I can send those as well.

I then played the wave files the radio while I was driving and narrowed the frequency that was the closest and went from there. It was a PITA, but I need to pat myself on the back because I nailed it dam near perfect. LOL!

 

[Varekai]

There is a formula, I'll send you the Excel file. I also, download a BUNCH of wave files with various HZ., Ill see if I can send those as well.

I then played the wave files the radio while I was driving and narrowed the frequency that was the closest and went from there. It was a PITA, but I need to pat myself on the back because I nailed it dam near perfect. LOL!

Lol that's awesome, thanks!I'll have to do that.

 

[Free Agent]

With all the talk about piping engine noise into the cabin these days and our knowledge of noise cancellation using the speakers. You think someone would come up with a program or "tune" for the head unit to listen for resonance and then play the corresponding opposite sound to cancel the noise out. You would still feel the vibration but the drone would be lessened or cancelled out. Would be a very simple solution to the problem of drone I feel. It could be as simple as buying a small noise cancellation device, plugging it into the AUX port and it would signal the speakers to cancel out the sound of drone. Of course it couldn't be used while you were listening to music or making a phone call but it should be a simple solution I would think.

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