[jmc]

no no no no no
we are not allowed to grow old
we have to stay young and fix/maintain our creaky jalopies

will probably need a finite element analysis though my concern is some of the weld joints during primary chassis assembly
parts of the chassis will “ring” differently if there is porosity or latent stress in some key weld points and will be a major recall in terms of long term integrity and short term crash safety

e.g. if the b pillar remains integrated with the floor pan during side impact then survival is high … but if say the lower welds fail then the side body itself becomes a weapon instead of a cage
the body integration and welding process is very telling for the mfa1 chassis
have not been able to find any details on the mfa2 its locked up it seems?

 

[DrOzCLA]

I have always understood that the B pillar vibration/rattle was simply a matter of plastic and metal components belonging to the seat belt retention device rubbing/knocking against each other over certain road conditions. I've not heard of any other reason, but I will ask the techs when I take mine in for the door stuffing party if there is any merit to the 'door to pillar' resonance theory.

 

[melquiades]

I'm not mechanically well-versed like the rest of you, so I won't argue whether or not it makes sense what the car audio guys said to me. However, I haven't heard any rattle noise coming from the B Pillar since the front doors have been sound-proofed. I can ask about this next Tuesday when I have the appointment for the rear doors.

 

[jmc]

… the techs may give you the “say what?” look

 

[jmc]

as for "damping pads" to lower the "ringing" of the doors ... i have 20lbs of this stuff
will need to ping the singing areas and damp those with the pads ... should be fun
hope 20lbs will be enough ... else the other half is just gonna have to go on a diet ... yikes!

 

[melquiades]

as for "damping pads" to lower the "ringing" of the doors ... i have 20lbs of this stuff
will need to ping the singing areas and damp those with the pads ... should be fun
hope 20lbs will be enough ... else the other half is just gonna have to go on a diet ... yikes!

View attachment 68456

I remember the car audio guys saying that the car will be 6-7 KGs heavier after the sound proofing. So I believe you should have more than enough material for dampening.

 

[jmc]

I remember the car audio guys saying that the car will be 6-7 KGs heavier after the sound proofing. So I believe you should have more than enough material for dampening.

that's good to know! per surface area and desired thud ... guess it will be around 5lbs for the front doors and 3lbs for the rears ... saving 2lb each for the (rather hollow) b pillars

 

[DrOzCLA]

as for "damping pads" to lower the "ringing" of the doors ... i have 20lbs of this stuff
will need to ping the singing areas and damp those with the pads ... should be fun
hope 20lbs will be enough ... else the other half is just gonna have to go on a diet ... yikes!

View attachment 68456

Our true pathfinder, I am always in awe of your confidence in attacking these things yourself jmc! Please take a couple of pics as you do it, I would be fascinated to see how these things sit within the door spaces, and particularly the B pillar, as I still have to get the Dealership to do those.

 

[jmc]

oh hell why not right? can only screw it up once or so anyway
it will be different on the 117 and 118 panels … different surface area, different crease lines, different acoustic shape, etc
though i believe (at least until i tackle it) the concept is to ping the expansive sections and test how a damping pad would change the acoustics and transient resonance (which our ears pick up as a solid or tinny door etc, and all those irritating fuzzing and buzzing and squeaking noises) then use a roller to create the final adhesive bond to keep the pad in place
my pet peeve is nature hates discontinuities and ringing always emanates from those, so have to design the pad shapes accordingly for each location … cant just slap on a bunch of rectangles or whatever
bottom line is to make a hifi recording, document that spectrum, then experimentally knock down the undesired noise peaks … a bunch of foam corrugated pads on the garage walls will help with that
but of course that will take too much time so the techs will rely on past experience with different panels and do a best effort … since anything (done within typical guidelines in their profession) would yield a “quieter” cabin
just comes down to whether you get say a -3dB improvement or -10dB for those particular sound bands that bother a typical person’s hearing the most
an old ghetto trick was to remove the door panels and spray lumpy undercoating
but of course the voc’s will kill ya or eat the components we now have on the panels plus the perpetual outgassing that would corrode parts we haven’t even considered yet
so its back to trimming and sticking pads
kinda makes ya appreciate what the audio guys do huh?
it’s an art alright

 

[melquiades]

^ Half the stuff you said went over my head. I would really appreciate if you can take pictures or videos of your sound proofing. Curious to see how this all comes together.

 

[jmc]

… Curious to see how this all comes together.

several members on this thread will get their panels edited by professionals shortly
hopefully they can document the critical portions of the work (especially the hidden parts once reassembled)
ok folks … please see if the audio techs can wear a 4k body cam and record it all

 

[melquiades]

several members on this thread will get their panels edited by professionals shortly
hopefully they can document the critical portions of the work (especially the hidden parts once reassembled)
ok folks … please see if the audio techs can wear a 4k body cam and record it all

But you're the only one planning to take off the B-Pillar 🤭

 

[jmc]

But you're the only one planning to take off the B-Pillar

Oh … dont hold your breath … when i get to it i will report back
though i usually grab a ton of pix so i know when and where i screwed up
will get to it cuz i have the seat belt guide update to accomplish

 

[jmc]

finally tracked down some older pix from 2016 ... a forum member really went all out to "quiet" the cabin for a pretty serious audio build
think his 45 could handle the extra mass heh

 

[mav238]

@jmc as always, no fear with tinkering the car for the sake of science and technology =)

I guess it depends on how old your car is, and if you are a hobbyist that love to find how to tweak your car to make it "better". I guess "better" is a relative term, what's a few rattles here and there for some is noise, is not an issue for others.

I can tell that the CLA is built with "light weight savings" in mind, as the hood , for example, is so light, I could lift it with one finger. The doors are stiff , but light as well, at least when compared to say a BMW door. Overall, I really don't find that my CLA is a clanky jalopy that irritate me to the point I need to do some drastic measures (like padding up the doors and like what JMC showed, stripping off everything and padding the overall safety cage structure). I rather save the 20lbs additional weight, and deal with occasional rattle and squeak. Especially with the gas prices hitting the roof nowadays.
I can imagine if folks here who find the CLA having rattles, is driving an electric version of the CLA, it will drive them nuts, because now, there is no engine sound to muffle out any little rattle or squeak coming off the car.
I would actually recommend folks here get the Magnaflow high performance replacement cat-back exhaust system to replace the factory exhaust, the increased exhaust sound will kill off any rattling sound, and also put a smile on your face.

 

[jmc]

@mav238
oh let me clarify those pix are from a 45 belonging to another forum member
though one day i may strip the chassis down cuz i do need to conduct some high current wiring
the padding would probably add ~100lb between the doors and the panels and trim pieces
my cla is quiet enough (after silicone oil droplets at the squeeky points) especially with the conti's and not rft's

the mag exhaust bothers me from one point - the input flow dynamics is a choke point

the becker is a better option it seems ... less path restrictive design

 

[mav238]

@mav238
oh let me clarify those pix are from a 45 belonging to another forum member
though one day i may strip the chassis down cuz i do need to conduct some high current wiring
the padding would probably add ~100lb between the doors and the panels and trim pieces
my cla is quiet enough (after silicone oil droplets at the squeeky points) especially with the conti's and not rft's

the mag exhaust bothers me from one point - the input flow dynamics is a choke point
View attachment 68485

the becker is a better option it seems ... less path restrictive design
View attachment 68486

The becker option, may not fit the CLA, given the dual muffler configuration which the CLA underbody probably not be able to fit.

 

[jmc]

that is a becker for the cla
the chambers are fairly small
lots of room under the rear section

 

[ans]

this is what you need almost straight through

Dual Sound rear muffler right-left, with flap For Standard bumper or "AMG Line" Package for MERCEDES C118 CLA 250 with valve, Dual Sound rear muffler right-left, with flap For Standard bumper or "AMG Line" Package

Dual Sound rear muffler right-left, with flap For Standard bumper or "AMG Line" Package for MERCEDES C118 CLA 250 with valve, Dual Sound rear muffler right-left, with flap For Standard bumper or "AMG Line" Package

www.supersprint.com

don't know if they do one for the 117 but i am thinking about one when my warranty runs out next year or may get one custom built as it maybe cheaper

 

[mav238]

@mav238
oh let me clarify those pix are from a 45 belonging to another forum member
though one day i may strip the chassis down cuz i do need to conduct some high current wiring
the padding would probably add ~100lb between the doors and the panels and trim pieces
my cla is quiet enough (after silicone oil droplets at the squeeky points) especially with the conti's and not rft's

the mag exhaust bothers me from one point - the input flow dynamics is a choke point
View attachment 68485

the becker is a better option it seems ... less path restrictive design
View attachment 68486

I checked the Becker official website, and they don't have anything current for the CLA. Where did you get this pic and info from?

Here's the link to the website search for Becker products for Mercedes:

Becker exhaust - Mercedes