Pressure Buffeting - Has anyone experienced it?

[cab]

Here is a link you might find interesting about the aforementioned Porsche Caymen's hatch. You will note references to a suspended weight that Porsche engineers added to the hatch in order to combat low frequency resonance. No such weight in the Model S hatch....

- Stopping the Hatch "Clunk" - Articles

 

[David.85D]

Here is a link you might find interesting about the aforementioned Porsche Caymen's hatch. You will note references to a suspended weight that Porsche engineers added to the hatch in order to combat low frequency resonance. No such weight in the Model S hatch....

- Stopping the Hatch "Clunk" - Articles

Awesome article and exactly what Tesla should be doing - modifying the weight and dampening of the hatch to eliminate the offensive mode.

 

[David.85D]

If anyone lives close to DC and wants to spend a weekend day playing with this, I have some audio test gear and an oscilloscope and the willingness to test different masses to find a way to eliminate this...,

Maybe we can turn the solution in for the bug bounty

 

[mspohr]

Here is a link you might find interesting about the aforementioned Porsche Caymen's hatch. You will note references to a suspended weight that Porsche engineers added to the hatch in order to combat low frequency resonance. No such weight in the Model S hatch....

- Stopping the Hatch "Clunk" - Articles

Looks like the weight created new problems that the owner went to great lengths to fix.
They sell a leaded dampening material which is sound insulation and that might be a good idea.

 

[cab]

Looks like the weight created new problems that the owner went to great lengths to fix.
They sell a leaded dampening material which is sound insulation and that might be a good idea.

I have to believe the Porsche engineers looked for a lot of other solutions before resorting to that fat suspended weight - adding weight is generally a "last resort" kind of thing. I am guessing it was discovered late in design and they couldn't fundamentally change the hatch in that generation.

It is important to note, however, that it isn't just mass in this case but a MOVING mass that actually responds to movement of the hatch Based on the descriptions, I think of it like a lead fishing weight suspended from a rubber band from solid surface (like the hatch)...bouncing up and down in a DELAYED response to hatch movement. It is anchored more solidly than that of course, but that's an extreme example of the movement.

Finally, one more item. When Tesla updates a part, they SEEM to keep the same part number but change the last digit (usually a letter) to the next highest letter. As an example, part 123-456 will be 123-456-A initially, but if revised it changes to 123-456-B, and so on. Anyway, in the hatch area the online catalog shows a number of parts associated with the hatch with B or C level "revisions". We have no way to know exactly WHAT Tesla changed for any given part, but the reports of this phenomena do appear to be reduced in later cars so MAYBE there is a change that they improved this.

In the attached picture, pieces 5, 7, 8, 9 and 10 are all at B or C level revisions. If you guys have a Tesla gallery nearby you might head to the gallery, pop the hatch on a new Model S and both a.) take pictures of these pieces and b.), see if the rubber stoppers in 10 - particularly 10 - and 7 seem noticeably more or less firm (or if it is more or less firm in its mounting). Last time I was at the gallery I was standing next to a Model X and someone opened the hatch. I noticed the hatch stopper equivalent to #7 on the Model S was markedly more firm on the new X. This made me feel pretty good about my own "solid rubber" mod above. Heck, you could just order the new parts...they might not be that pricey.

There are other revisions in the latch and striker part numbers as well.


Online Catalog (under Model S see section 11: closure components, 1133 Closure Assist Mechanisms and Hinges - Lift Hinges and Fittings)
https://epc.teslamotors.com/#/login

 

[David.85D]

Fwiw, early BMW X5 had hatch rattle problems (more like the Porsche problem, different than the MS problem I think) that they solved with new spring loaded stoppers that kept tension over time. If the Tesla stoppers aren’t very pricey, might make sense to replace them every once in a while

 

[Audiosaurus]

Just one other quick follow-on post, which may be review of prior art for some of you. I tried folding the back seats up and dow, no effect (if anything, the LF noise / booming gets worse when they are folded down). I also experimented a little with filling the luggage area (below the divider / cover) with baffling, to minimal effect. I reduced the baffling I am using to a single rolled-up comforter wedged between the tops of the back seats and the ceiling of the car, and that works nearly as well as filling the whole back compartment up with damping material of various sorts. So, +1 for TSLACG's idea. I think you just have to damp that first axial "room mode." Using the backity-uppity camera for full-time rear view helps a little with visibility once you acclimate to it. Still not ideal.

 

[cab]

Just one other quick follow-on post, which may be review of prior art for some of you. I tried folding the back seats up and dow, no effect (if anything, the LF noise / booming gets worse when they are folded down). I also experimented a little with filling the luggage area (below the divider / cover) with baffling, to minimal effect. I reduced the baffling I am using to a single rolled-up comforter wedged between the tops of the back seats and the ceiling of the car, and that works nearly as well as filling the whole back compartment up with damping material of various sorts. So, +1 for TSLACG's idea. I think you just have to damp that first axial "room mode." Using the backity-uppity camera for full-time rear view helps a little with visibility once you acclimate to it. Still not ideal.

Just clarifying - Is the comforter positioned between the seats and ceiling or between the hatch cover and glass of the hatch (i.e. is it applying pressure to the glass/hatch at all)?

In one of my earlier posts above I mentioned the absolute nightmare GM SUV owners were having with this same issue. One of the attempted fixes involved reinforcing the roof bows. One of the theories is that GM's switch to thin high strength steel resulted in increased NVH and various panels (like the roof) would actually flex (almost oil canning) when road or exhaust (particularly with cylinder deactivation) was introduced. I think that anything which makes a car more "stiff" in terms of structure helps to isolate and/or reduce the boominess. The comforter could be disrupting the sound wave itself OR it could be that it is simply stiffening something (like the roof or hatch) up by applying pressure. I jammed pillows on top of the parcel shelf and noticed a reduction in boom, but I came to believe it was because it was helping to minimize hatch movement (vs. blocking or absorbing sound waves). As you can tell, I've done way too much research on this.

Oh and for fun, I actually ordered the Porsche hatch dampening weight. Unfortunately, it is backordered and it will be a couple of months before it comes in. I don't really anticipate being able to successfully adapt it to the Tesla hatch, but you never know. My motivation is a bit low since I am reasonably happy with the firmer rubber adjusters now. My next project will likely be more sound deadener / absorber - this time in the doors (for road noise).

 

[dark cloud]

Oh and for fun, I actually ordered the Porsche hatch dampening weight. Unfortunately, it is backordered and it will be a couple of months before it comes in. I don't really anticipate being able to successfully adapt it to the Tesla hatch, but you never know. My motivation is a bit low since I am reasonably happy with the firmer rubber adjusters now. My next project will likely be more sound deadener / absorber - this time in the doors (for road noise).

My understanding of it is that it is not so much a dampener but a noise cancellation technique: it produces the same frequency as the hatch noise, but 180 degrees out of phase and thus cancels the wave. How do you know the Tesla hatch produces the same frequency as the Cayenne? Doesn't hurt to try I suppose..

 

[David.85D]

For anyone interested, this explains a tuned mass damper. The extra small mass and it’s spring should be tuned to the resonance frequency you are trying to reduce.

Tuned mass damper - Wikipedia

 

[cab]

My understanding of it is that it is not so much a dampener but a noise cancellation technique: it produces the same frequency as the hatch noise, but 180 degrees out of phase and thus cancels the wave. How do you know the Tesla hatch produces the same frequency as the Cayenne? Doesn't hurt to try I suppose..

I definitely have no idea if it will work (although I suspect the frequencies are all in a similar range). The bigger issue will likely be trying to figure out how to mount it in a similar plane- or at all. The Cayman has a huge metal to glass ratio compared to the S.

Oddly enough, I actually own ANOTHER car with a tuned damper. It is a 67 Firebird convertible. These cars, the convertibles specifically, when introduced had way too much cowl shake so GM added FOUR 25 lbs dampers to the car (yeah, 100 lbs total). They are affectionately referred to as "cocktail shakers" as they are round, oil-filled sealed cylinders with a weight and a spring in them. Pic and write-up below:

Description of "Cocktail Shakers":
On the corners of convertibles there are what's called "cocktail shakers" or vibration dampeners which were originally installed on every first gen convertible Camaro to help prevent vibrations. They were installed due to a very flexible body in the convertible models because of the lack of the roof structure. Some reinforcement was added to the convertible rockers and floors but it wasn't enough to prevent all vibration problems. The cocktail shakers are large cans with a suspended mass on a spring in a viscous fluid that are mounted on the corners - 4 in all. They were tuned to a resonant frequency of the convertible that caused the vibration problems. When the body was subjected to loading that would otherwise tend to make it oscillate, much of the energy was instead absorbed by the motion of the masses in the cocktail shakers - which reduced the vibration in the convertible body. The cocktail shakers weight about 25 pounds each

Pic of one in the trunk:

 

[Audiosaurus]

Hey y'all.

At present I have the comforter wedged between the tops of the back seats and the ceiling, not appreciably touching the glass...in fact, I moved it because I thought maybe the extra pressure against the lift gate could be causing the damping effect. I've spent a little time fooling around with the stops on the lift gate so I am pretty sure it is snug, but there's always the possibility of a second mode or window vibration. Anyway...still seems like it's a standing wave in the cabin.

 

[mspohr]

Hey y'all.

At present I have the comforter wedged between the tops of the back seats and the ceiling, not appreciably touching the glass...in fact, I moved it because I thought maybe the extra pressure against the lift gate could be causing the damping effect. I've spent a little time fooling around with the stops on the lift gate so I am pretty sure it is snug, but there's always the possibility of a second mode or window vibration. Anyway...still seems like it's a standing wave in the cabin.

Dealing with resonance is tricky and it's easy to make things worse if you get it wrong. You don't want to add resonance at the current frequency. You need to cancel out the resonance.
I think your current approach of adding dampening is better. Perhaps some mass weighted dampening material would work.

 

[cab]

Well, the Cayman hatch damper I ordered arrived. It will likely be several weeks before I get around to messing with it. It appears to weigh about 2 lbs and is about 8” X 3 1/4”. The center rubber rings are fairly flexible. it takes almost no pressure to tilt the little disk as you see me doing in the second pic.

 

[sgarza1]

Well, the Cayman hatch damper I ordered arrived. It will likely be several weeks before I get around to messing with it. It appears to weigh about 2 lbs and is about 8” X 3 1/4”. The center rubber rings are fairly flexible. it takes almost no pressure to tilt the little disk as you see me doing in the second pic.
View attachment 366712 View attachment 366713

Cab, just got my model S a few weeks ago, and am having serious headache issues due to this buffeting, I live in Rockwall saw you live in Grapevine- any luck with the Porsche mount? I am also interested in the rubber stoppers you made-

 

[cab]

Cab, just got my model S a few weeks ago, and am having serious headache issues due to this buffeting, I live in Rockwall saw you live in Grapevine- any luck with the Porsche mount? I am also interested in the rubber stoppers you made-

Haven’t gotten around to trying the Porsche weight (life gets in the way, and my rubber stopper fixed addressed “enough” of the issue to make it a lower priority for me). The rubber stoppers are so easy, it is totally worth a try. In post 69 I reference it...note: they are the 3/4” dowel size I mention in that opening paragraph (not the 1/2” rubber cord I was going to try to replicate the rope idea from another member). I basically unscrewed the old stoppers, did some rough measurements on the depth of that hole and height I would need above it and then used my dremel tool to whittle down the dowel body to fit into the hole. The piece of rubber is effectively shaped like a fat letter “T” with the top of the T sitting above the hole and what you see in post 78.

 

[RonaldT]

Sorry I got here so late, just purchased a S in March. A set of golf clubs in the trunk will knock down a lot of this noise, seriously.
R

 

[eyedrop]

Has anyone tried putting a cylindrical shaped acoustic bass trap (similar to home theater stuff) for knocking out the bassy sounding road noise in the cabin?

I also noticed the sound system frequency response has a large peak at around 40hz or so... Maybe try using a hook and loop to attach bass trap to back seat where the node is...

 

[cdnev]

I do not yet have a Model S, but am very keen to get one. This low frequency issue would be a problem if it bothered my wife. I also wonder if the Raven suspension upgrades have helped at all. Finally, even if you don't hear low frequency noise, there can be other serious effects of vibration transmission on the driver, see:

https://www.cbc.ca/radio/quirks/jul...-you-with-sleep-inducing-vibrations-1.4753032

Does anyone know if this low frequency driver drowsiness issue has been looked at when comparing ICE cars with BEVs? Have Model S owners noticed any difference in the drowsy factor between their Tesla and past cars they've owned when on long road trips?

From the story above the researchers indicate factors that influence the vibrations we feel on the road include:

• A vehicle's tires and suspension.
• Car seat design.
• Engine vibration.
• Road surface.
• Speed.

Since nature of three of the five issues are/can be quite different in a Tesla, it seems like an important area to focus on.

This thread has been extremely helpful to me.

 

[brookman]

I had that same buffeting and saw a thread mentioning the rubber stops on the rear hatch, one of mine was completely screwed all the way up so that it did not touch when the hatch was shut. I adjusted it using detailing clay until the clay was smashed and the problem seems to be gone. If I ever have to do it again I would put a piece of blue tape down first.