Slon Wall NVH

[heinzboehmer]

Question for those running the Slon rear wall/bulkhead: have you noticed increased NVH (emphasis on the N) after the install?

In my car, the wall was acting as a speaker and resonating quite loudly at ~201 Hz. Was very obvious at speeds >60 mph with the rear seats folded down.

Found that if you put light pressure on two spots on the left and right sides of the brace, the resonance goes away completely:

Over engineered a fix for my car, but am now wondering if two of those snare moongel dampers (or similar) placed in those two spots would be enough to quiet it down. Anyone with this mod want to give that a shot and report back?

[Advorsor]

Zero here

[heinzboehmer]

Zero here

Hmm, what subframe bushings are you running? Any vincebar style reinforcement installed?

[zivagolee]

#trackcar

[Estoril]

What is the purpose of it in a car with rear seats?

[Slideways]

What is the purpose of it in a car with rear seats?

"30% increase in torsional rigidity of the chassis"

[Advorsor]

Hmm, what subframe bushings are you running? Any vincebar style reinforcement installed?

No vincebar and IIRC, subframe bushings are standard Powerflex poly

[heinzboehmer]

No vincebar and IIRC, subframe bushings are standard Powerflex poly

Interesting. I'm guessing the bolt through design of the front vincebar cups combined with my solid subframe bushings contributed to my NVH. Vibrations at the subframe travel through all the solid stuff and resonate at the panel.

Obioban IIRC you have solid subframe bushings, a vincebar and this brace. Yours behave similarly?

[Obioban]

Interesting. I'm guessing the bolt through design of the front vincebar cups combined with my solid subframe bushings contributed to my NVH. Vibrations at the subframe travel through all the solid stuff and resonate at the panel.

Obioban IIRC you have solid subframe bushings, a vincebar and this brace. Yours behave similarly?

Not that I’ve noticed, but I haven’t had the seats folded down since I installed the wall. I was thinking about going for a drive with them down after seeing your post, but taking the child seat out is a big pain.

[Obioban]

What is the purpose of it in a car with rear seats?

Per BMW, chassis stiffness:

• BMW E46 Sedan (w/o folding seats): 18,000 Nm/deg
• BMW E46 Sedan (w/folding seats): 13,000 Nm/deg

Purpose is getting some of that for ourselves.

[heinzboehmer]

What is the purpose of it in a car with rear seats?

"30% increase in torsional rigidity of the chassis"

With measured results!

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/136678-slon-workshop-torsional-rigidity-platform-e46-m3-new-experience-tests-tech-info#post137644

Not that I’ve noticed, but I haven’t had the seats folded down since I installed the wall. I was thinking about going for a drive with them down after seeing your post, but taking the child seat out is a big pain.

Yeah fair enough. Getting back there with the nogaros is no fun. Let me know if you do test this, fairly sure a small square of damping material on the wall is all that's needed to quiet the resonance. If not, seems pretty easy to find a way to wedge something between the wall and seat backs at those two points.