Sebljo

Just picked up a new 991 from the dealer this afternoon. On the way home, while driving at approximately 35 MPH with the sun roof in the full open position, I felt and heard strong low frequency air vibrations pulsing inside the cab. They disapeared whenever I sped up or slowed down. Opening the windows a crack didn't help. Anyone else experience this wierdness, and if so, is there a fix? Thanks all.

chuckbdc

Haven't felt that. If we survive Sandy I'll try it.

I have found that there is a ridiculously annoying harmonic with one window all the way down at highway speeds: opening the other window a bit or popping up the back of the sunroof fixes it.

Detroit Shooter

I have experienced the same thing. I have not experimented with cracking a window or 2. I had them tinted and they suggested a couple days before rolling them down.

deturney

I have a very early 2012 with no sunroof problems. Call PCNA and see if yours is one that has a campaign regarding the sunroof/sunroof wind deflector.

Mike in CA

I've had several cars that experience a "booming" sound when the sunroof is open all the way, including my 997.2 Carrera. The manual even mentions that the roof opens to it's best position relative to noise when you use the "one touch" feature, although you can open it all the way by pressing the button again. Another way to control the noise is to crack the window when the roof is fully open.

It's surprising that some folks say they haven't noticed this in the 991 since based on my experience with sunroofs it can be pretty normal.

rnl

No noise here. Mine is a may 2012 build

rijowysock

without moonroof opening one window in my 991 was horrible.. the pass door would shake violently... also lowering both windows 100% could not be driven above 40... too much buffering... the old mirrors were better at canceling the wind

Sujan Patel

I get the same noise with windows open (sunroof closed) at speeds over 80mph. Anyone else experience this?

deturney

In my opinion this buffeting/booming problem should not be considered as normal on any factory power sunroof (no offense intended).

It may seem unusual, but 2 supposedly identical cars with supposedly identical sunroofs can sound quite different in regards to buffeting noises. Even to the extreme of one being very annoying while the other exhibits no buffeting problem at all.

I know this because many years ago I worked for a business that installed aftermarket power sunroofs. I eventually became so good at trouble shooting that I was requested to work on many factory sunroofs at Dealerships (mostly high-end American cars).

There are so many things that affect sunroof wind noise, some of them having to do with the built in wind deflector, among other things. Is it rising all the way to it's proper height? Does it rise too high? Is there sufficient tension on it to keep it at its proper height at all speeds?

That's why I suggested in a previous post that owners who are having these "wind noise" problems start by calling PCNA and find out if their car is one that is included in the Campaign that is specific to the Wind Deflector (I think it is #WC-40, but I am not sure about that). That is where I would start if mine had this problem.

mtbscott

I haven't noticed any weird buffeting or harmonics on my car yet, and with the beautiful weather we've had here since I got it, my windows and sunroof have been open a lot. I am getting a bit of a rattle when the roof is open that seems to be coming from it. Otherwise my car is tight as a drum, not so bad that I want to make a special trip back to the dealer for it.

Mike in CA

No offense taken. I've experienced the booming effect to various degrees, dependant on speed, how far the sunroof is open, whether the windows are also open, etc., in every sunroof equipped car I've owned including 3 911's. Maybe they were all poorly designed or malfunctioning in some way. I've also heard complaints from others on this issue.

The link below is to a patent application for a device to reduce the acoustic effect generated by air rushing past an open sunroof. I think it's interesting because it rather clearly lays out what causes the problem (the passenger compartment of the car acts like a Helmholtz resonator; think of the noise you make when you blow over the top of an empty bottle) and what some of the solutions might be.

Different cars can be expected to demonstrate the problem to different degrees, and as your experience suggests things like properly designed wind deflectors can help mitigate the problem, although I've found that it's never completely eliminated. Obviously I haven't driven every car out there and probably don't have the range of experience with this that you do.

In any event, my original point was that this problem is not particularly unusual. You may be right that Porsche has a fix of some kind. I wish the OP good luck with that.

http://www.faqs.org/patents/app/20120073898

deturney

As you might imagine, after working with and repairing power sunroofs for 11 years I don't really care much about having one in my own car. Therefore I probably don't use mine as much as you do. But being an ex-sunroof guy I have given it a lot of tests to see if all was OK with it. It figures the guy that doesn't care about them gets one that is quiet, mine is better than I expected.

If I ordered my 991S I would not have chosen a sunroof, but my car was an early 2012. The 2013's could be ordered when I bought mine new off a Dealer's lot. I got a pretty good deal and the sunroof should probably help on resale.

Mike in CA

Actually, I've come around to your point of view. If I could have ordered my 997.2 without a sunroof I would have, as I don't use it much at all and it puts extra weight in exactly the wrong place. I'm glad Porsche has decided once again to make it optional and my next 911 won't have one, better resale or not.

simsgw

Hmmm. And I went the other way and bought a Cabriolet, Mike. Two different solutions. I was going to explain that it isn't a flaw when sunroofs permit that booming effect, just a sign of very good aerodynamics being interrupted with an opening into a resonant cavity. But Mike did a good job already.

The solution -- besides a closed coupe or a cab -- is to disrupt the aero in some way that keeps the resonance from forming. Various lip devices (opening, not driver) can do that, as can fiddling with the windows if you really can't slow down or speed up when the resonance forms. I didn't check the patent Mike references, but I'm sure it amounts to a clever way to block the resonance at the primary windspeed, but then adjust to block it forming at other speeds as well. And it might adjust by adapting to changing windspeeds if it's really clever. Either that, or a little robot hand reaches down with a terse note: "Have you considered a cabriolet?"

Gary

Mike in CA

You're very close Gary, but then you have great engineering instincts so that's not surprising. Without going into detail, it appears the patent describes a cylindrical deflector with holes, a microphone, and an independant air source to introduce varying amounts of air into the device to adjust airflow and keep the resonance from forming, just as you suggested. I don't know how practical it would be, but at least the application gave a good description of the forces at work.

To your point about different solutions, after owning my first roadster (a Boxster S) for a couple of years I confirmed that I wasn't really a Cab person. Given that I don't even use sunroofs much, I guess I should have figured that out earlier. I'm sure, though, that a Cab will be exactly right for you.