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Discussion Starter · #81 ·
StainlessWorks wasn't helpful at all. Still trying to work with Dynomax. 馃

It really is specific to load. Here's 50mph @ ~2100rpm on a slight grade, then leveling off. Pretty much right on 80Hz here.
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With something that specific, would a tuned mass damper work well enough? I know BMW and MB use them. I'll keep an eye out for one labeled at 80Hz
 

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no, they get a mounted to a bracket that is attached to the exhaust, ill see if i can find one on a lift at work and snap some pictures.
 

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Yes something exactly like that. My understanding is a bit of both. It definitely helps with frequency transferred into the cabin but if that's changed then there will be an audible change to the exhaust note. To what effect? Not a clue, that's way above my education and understanding. All I know is without them on some cars there are unwanted harmonics audible in the cabin of the car.
 

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Discussion Starter · #87 ·
Neat. Maybe both?

Mopar part 52103612AA seems to be frequently recommended to address 2000-2400rpm resonance.
Toyota part 17581-31010 seems to be commonly used for 2200rpm resonance.

Sadly, both seem to be discontinued. I'd guess both are available in some form used though. I found some references to Ford dampers, but the general consensus I've seen so far has been that they don't help much.

I heard back from Dynomax finally and their suggestion is to add an additional muffler or resonator as far upstream in the exhaust as possible. They were reluctant to recommend anything specific. That may be a kind of fortuitous recommendation, since it seems like I can probably fit something slightly larger than 4" in diameter up there. I don't see a ton of options in that space but, unlike out back, something like a Vibrant Ultra Quiet res should fit in the area where the shift box is if my measurements are correct.

--Matt
 

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no, they get a mounted to a bracket that is attached to the exhaust, ill see if i can find one on a lift at work and snap some pictures.
Yes something exactly like that. My understanding is a bit of both. It definitely helps with frequency transferred into the cabin but if that's changed then there will be an audible change to the exhaust note.
Sounds interesting. So one mount it directly on the muffler or the part of the exhaust where the drone can be located best?
 

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It really is specific to load. Here's 50mph @ ~2100rpm on a slight grade, then leveling off. Pretty much right on 80Hz here.
Thanks for sharing Matt. Where and how did you measure the noise spectrum?
 

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Like I said, if I have one come in I'm going to take some photos. Get some references. Mercedes stamps it with part numbers and frequency data right on it. Unfortunately it's not provided in the parts catalogue. I think there is one or two in the 80-90hz range there's on in the 100 something range. I wanted to do it vs the helmholtz resonator I added. It's works but it's not optimized and it's REALLY annoying outside of the car at that frequency. I vaugly remember 107hz, it gets super tinny sounding outside of the car. That makes sense though since it's sound bouncing off of stainless steel pipe reflecting and multiplying in a way.
 

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Discussion Starter · #91 ·
Sounds interesting. So one mount it directly on the muffler or the part of the exhaust where the drone can be located best?
It really seems to vary from vehicle to vehicle. Many seem to have them way up front, but other cases (like Ford Raptor trucks) seem to put them toward the back.


104095

104096


Thanks for sharing Matt. Where and how did you measure the noise spectrum?
It was measured with an app inside the car with the windows halfway down.

--Matt
 

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Had a couple cars in finally with some dampers on it.
A2514910347 --66HZ
A2514910447 --63HZ
A1644910047 --48HZ
A1644910147 --36HZ
A1644910447 --90HZ
A2034910347 --74HZ
A1644910947 --92HZ

also good p/n are
A1644910847

No idea what the hz stamps are though, still doing some digging through that.

Also the bolt for them is M8 p/n A0019904800

I will update this post as I find the specs on more of them. There are ALOT of valid part numbers for these.
 

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Discussion Starter · #93 ·
BMW seems to have some which might be promising...

80Hz - 33176856504
81 Hz - 18303443977
83 Hz - 18103412864
88 Hz - 18107544260

The former 2 are for vehicles with 3L engines, the latter 2 are for vehicles with 2L engines. 81 Hz seems closest to my hot spot.

They all seem to be attached by a bolt to a threaded bracket on the piping...not sure how to attach without such facilities.

--Matt
 

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Thanks for your shared research result @mattkosem!

They all seem to be attached by a bolt to a threaded bracket on the piping...not sure how to attach without such facilities.
Depends on their design, what forces are created and if these need external bracket support. Do you have pictures of one of them you have in mind?
 

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Discussion Starter · #95 ·
As far as I can tell from the parts diagrams they all look pretty much like this.
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The diagrams (with one odd exception) all show them bolting onto a bracket of some sort that appears to be welded onto piping somewhere, which holds them parallel to the pipe. Some are near the front, others near the back.

One of them affixes to the downpipe on an X3 on the piece just south of the center of this diagram:

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Another model has it on the midpipe (8 in the diagram):
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Guess some sort of plate would likely need to be welded onto the pipe somewhere. Space around there is at a premium on an EG though. 馃槣 I'm sure not seeing an obvious spot where some metal could hang 3" off of the pipe in the underbody. Not sure if it'd work back there, but I think it could probably fit on the back of the muffler nearby the pipe inlet.
 

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Discussion Starter · #97 ·
Something like this seems like it might work for mounting the damper. Given that it doesn't have to be welded on, it could also be moved if necessary to find an appropriate spot.


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Discussion Starter · #98 ·
Well, gulp, I decided to take the plunge. That mount was the last piece I was looking for.

81Hz seems to be dead center of the middle of my frequency spike. I grabbed one of those mounts plus the associated pieces from BMW. Boy I hope this works. It's like $130 for all this stuff. 馃

18-30-3-443-977​
Vibration Absorber 189999​
18-40-3-412-867​
Vibration Damper Heat Shield​
18-40-7-540-023​
Vibration Damper Screw​
 

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Well, gulp, I decided to take the plunge. That mount was the last piece I was looking for.

81Hz seems to be dead center of the middle of my frequency spike. I grabbed one of those mounts plus the associated pieces from BMW. Boy I hope this works. It's like $130 for all this stuff. 馃

18-30-3-443-977​
Vibration Absorber 189999​
18-40-3-412-867​
Vibration Damper Heat Shield​
18-40-7-540-023​
Vibration Damper Screw​
thank you for posting part numbers. gotta have those part numbers to keep information alive and giving. I am interested to see how this works for you.
 

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Discussion Starter · #100 ·
Gonna need to trim this bracket a bit, but it seems like it should generally do. It's a big sturdy piece, and can be welded in-place where it needs to go if it works.

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