E90 rear window design flaw?

RaulZero · 05-04-2006, 01:23 PM

I was giving my parents a ride in the new car and my mother, sitting in the back seat, decided to open her window. All the other windows were closed. We were going about 50mph. As soon as she opened the window the cabin started to reverberate with a VERY powerful low frequency rumble. Probably about 5Hz. The sound was unbearable and I thought it might burst my eardrums. It went away after she closed the window.

It was a bit embarassing. Anyone else notice this?

agarbati · 05-04-2006, 01:29 PM

My old Corolla does this. My E90 does this too. So did my old Accord.

I suspect it is just inherent if you open one of the rear windows while all others are closed. I'm not intelligent enough about fluid dynamics to expound the issue but perhaps someone will chime in.

rchanou · 05-04-2006, 01:32 PM

it's just the pressure inside the cabin from one window being open

Scorviss · 05-04-2006, 01:33 PM

it's called buffetting, most cars do this, but it is most prevalent on sedans from what i've experienced.

kobechrome · 05-04-2006, 01:34 PM

I've had this in every single car. It's esp bad in the e90 though... I think smaller cars get the worst of it.

Broken1 · 05-04-2006, 01:35 PM

Quote:

Originally Posted by RaulZero

I was giving my parents a ride in the new car and my mother, sitting in the back seat, decided to open her window. All the other windows were closed. We were going about 50mph. As soon as she opened the window the cabin started to reverberate with a VERY powerful low frequency rumble. Probably about 5Hz. The sound was unbearable and I thought it might burst my eardrums. It went away after she closed the window.

It was a bit embarassing. Anyone else notice this?

Find me a car that doesn't buffet at 50mph.

Zenit77 · 05-04-2006, 01:48 PM

Same used to happen on my E46; there is nothing we can do

shragon · 05-04-2006, 01:50 PM

it happens.

SteveMD · 05-04-2006, 01:52 PM

Crack the sunroof or one other window and it goes away.

Flyingdwarf · 05-04-2006, 01:55 PM

Yep, this just happens. If you crack one of your front windows open just a little it should be enough to stop it as it will reduce the pressure and let the air flow. Basically it is because air is trying to get in and out of the same hole. Not tried it in my E90 though so dont know if it is worse than any other cars I have driven. I feel a little experiment coming on. Hope your mum's ears are OK!

jsapir · 05-04-2006, 01:58 PM

I call it the helicopter effect

edy74 · 05-04-2006, 02:13 PM

U have to open the front window on the same side, just a lil bit..........

E90330iS · 05-04-2006, 04:52 PM

I have had this problem in all 3 BMWs my family own, not the E90's fault!

BiggieJ · 05-04-2006, 05:18 PM

i posted about this problem a while back. and yes all cars buffet but the one in the e90 is deafening. my theory is that its the downside of haveing the Sub in the cabin rather than in the trunk. so the vacume created reacts with the sub under you seat. i think its kinda crappy but at least now i know its "normal."

kprince · 05-04-2006, 05:26 PM

Like everyone else has said. Same problem in E46. Rented an Audi A4 last week at LAX, discovered same problem on highway to Death Valley.

Laplacian · 05-04-2006, 07:07 PM

Look up "Bernoulli's Law". In layman's terms, high fluid speed leads to low pressure, low speed leads to higher pressure. The speed of the air on outside is high, inside is low, so the pressure on the outside is low and the pressure on the inside is high. (Technically, Bernoulli's Law applies only to incompressible fluids, but the air is not being compressed THAT much.) This causes the air from inside the cabin to want to flow out, so some does, but when enough of it does, it creates a pressure gradient going the other way, so some air flows back in. The effect is cyclic and the frequency probably depends on the shape & volume of the cabin, aerodynamics of the car, etc. The amplitude should increase with increasing speed (again, assuming incompressiblity). The frequency on the E90 is especially annoying; same for the E65. My dad's Expedition is not as bad, however.

Like others said, crack another window or sunroof.

David328M-Sport · 05-04-2006, 07:16 PM

My E90 does it, my old E46 did it (still does - wherever it is now) and my old e36 did it it too.

My wifes MB C180K does it as well.

Nothing to worry about. I just dont have a back passenger window open without another to null out the effect.

Speedy E90 · 05-04-2006, 07:34 PM

Tilt open sunroof....and it will stop.

Macfreak7 · 05-04-2006, 07:58 PM

It's a safety feature.

nyyankee · 05-04-2006, 08:10 PM

Wow this exact thing happened to me today when I was driving with my sis. She thought the stero had broken...lol

ages944 · 05-05-2006, 12:59 AM

Quote:

it's called buffetting, most cars do this, but it is most prevalent on sedans from what i've experienced.

... how exactly do you open the rear window in a coupe???

lol, sorry, couldn't help it.

Broken1 · 05-05-2006, 02:14 AM

Quote:

Originally Posted by ages944

... how exactly do you open the rear window in a coupe???

lol, sorry, couldn't help it.

With the electric window button?

The BMW Coupe windows open outwards. They do a very good job at reducing buffetting! :-)

05-04-2006, 01:23 PM	#1
RaulZero RaulZero 1 Rep 5 Posts Drives: 330xi E90 Join Date: Mar 2006 Location: Richmond, VT iTrader: (0)	E90 rear window design flaw? I was giving my parents a ride in the new car and my mother, sitting in the back seat, decided to open her window. All the other windows were closed. We were going about 50mph. As soon as she opened the window the cabin started to reverberate with a VERY powerful low frequency rumble. Probably about 5Hz. The sound was unbearable and I thought it might burst my eardrums. It went away after she closed the window. It was a bit embarassing. Anyone else notice this? __________________ E90 330xi Arctic Metallic
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05-04-2006, 01:29 PM	#2
agarbati Second Lieutenant 39 Rep 279 Posts Drives: E90, Saph Blk 330i Join Date: Apr 2005 Location: Minneapolis iTrader: (0)	My old Corolla does this. My E90 does this too. So did my old Accord. I suspect it is just inherent if you open one of the rear windows while all others are closed. I'm not intelligent enough about fluid dynamics to expound the issue but perhaps someone will chime in.
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05-04-2006, 01:32 PM	#3
rchanou Private First Class 11 Rep 186 Posts Drives: 325i Jet Black Join Date: Feb 2006 Location: Long Beach, CA iTrader: (0) Garage List 2006 325i [0.00]	it's just the pressure inside the cabin from one window being open
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05-04-2006, 01:33 PM	#4
Scorviss Private First Class 55 Rep 167 Posts Drives: OG M2, G80 on order Join Date: Jan 2006 Location: Silicon Valley iTrader: (1)	it's called buffetting, most cars do this, but it is most prevalent on sedans from what i've experienced. __________________ I like cars
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05-04-2006, 01:34 PM	#5
kobechrome Captain 38 Rep 699 Posts Drives: 2013 F30 335xi Join Date: Dec 2005 Location: Ashburn, VA iTrader: (0) Garage List 2013 BMW 335xi Sport [0.00] 2013 Lexus RX 350 [0.00] 2006 BMW 325i [0.00]	I've had this in every single car. It's esp bad in the e90 though... I think smaller cars get the worst of it. __________________
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05-04-2006, 01:48 PM	#7
Zenit77 Enlisted Member 0 Rep 34 Posts Drives: 2006 BMW E90 330i Join Date: Sep 2005 Location: Brooklyn, NY iTrader: (0)	Same used to happen on my E46; there is nothing we can do
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05-04-2006, 01:50 PM	#8
shragon Moderator 497 Rep 27,441 Posts Drives: BMW Join Date: Oct 2005 Location: Bay Area, CA iTrader: (7)	it happens. __________________ www.cardomain.com/id/shragon
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05-04-2006, 01:52 PM	#9
SteveMD Colonel 196 Rep 2,485 Posts Drives: 2016 F10 535i MSport Join Date: Dec 2005 Location: Raventown! iTrader: (3)	Crack the sunroof or one other window and it goes away. __________________ 2006 E90 330i (retired) 2009 E90 335i (retired) 2012 E70 X5 50i M Sport (retired) 2016 F10 535i M Sport
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05-04-2006, 01:55 PM	#10
Flyingdwarf First Officer 14 Rep 187 Posts Drives: 320d M Sports Join Date: Feb 2006 Location: North Yorks, UK iTrader: (0)	Yep, this just happens. If you crack one of your front windows open just a little it should be enough to stop it as it will reduce the pressure and let the air flow. Basically it is because air is trying to get in and out of the same hole. Not tried it in my E90 though so dont know if it is worse than any other cars I have driven. I feel a little experiment coming on. Hope your mum's ears are OK! __________________ E90 320d M Sport \| Black Sapphire \|6 Speed Manual \| Blue Shadow Cloth/Alcantara \| 193s \| Individual Sun Protection \| Rain Sensor + Automatic Headlight Control \| 6 CD \| Hi-Fi Loudspeaker System
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05-04-2006, 01:58 PM	#11
jsapir White Diamond 3 Rep 18 Posts Drives: 330xi Alpine White/Terra Join Date: May 2006 Location: Toronto, Canada iTrader: (0)	I call it the helicopter effect
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05-04-2006, 02:13 PM	#12
edy74 Captain 133 Rep 767 Posts Drives: CUSTO///M E90 , 640d xdrive Join Date: Feb 2006 Location: Bucharest iTrader: (2) Garage List 2006 318i [9.00]	U have to open the front window on the same side, just a lil bit..........
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05-04-2006, 04:52 PM	#13
E90330iS Major General 143 Rep 6,333 Posts Drives: BMW M4 Join Date: Jan 2006 Location: Arcadia, California iTrader: (56) Garage List 2006 330i [0.00]	I have had this problem in all 3 BMWs my family own, not the E90's fault! __________________ 2017 BMW M4 DCT Lease Transfer: https://f80.bimmerpost.com/forums/sh...8#post23736398
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05-04-2006, 05:18 PM	#14
BiggieJ Second Lieutenant 62 Rep 239 Posts Drives: e92 335 ZSPZPPOPP Join Date: Nov 2005 Location: SoCal iTrader: (0)	i posted about this problem a while back. and yes all cars buffet but the one in the e90 is deafening. my theory is that its the downside of haveing the Sub in the cabin rather than in the trunk. so the vacume created reacts with the sub under you seat. i think its kinda crappy but at least now i know its "normal."
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05-04-2006, 05:26 PM	#15
kprince New Member 2 Rep 14 Posts Drives: 330i SG/Terra ZHP Join Date: Mar 2005 Location: Boston iTrader: (0)	Like everyone else has said. Same problem in E46. Rented an Audi A4 last week at LAX, discovered same problem on highway to Death Valley.
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05-04-2006, 07:07 PM	#16
Laplacian Private First Class 14 Rep 182 Posts Drives: 2006 330i Join Date: Jan 2006 Location: Los Angeles, CA iTrader: (0)	Look up "Bernoulli's Law". In layman's terms, high fluid speed leads to low pressure, low speed leads to higher pressure. The speed of the air on outside is high, inside is low, so the pressure on the outside is low and the pressure on the inside is high. (Technically, Bernoulli's Law applies only to incompressible fluids, but the air is not being compressed THAT much.) This causes the air from inside the cabin to want to flow out, so some does, but when enough of it does, it creates a pressure gradient going the other way, so some air flows back in. The effect is cyclic and the frequency probably depends on the shape & volume of the cabin, aerodynamics of the car, etc. The amplitude should increase with increasing speed (again, assuming incompressiblity). The frequency on the E90 is especially annoying; same for the E65. My dad's Expedition is not as bad, however. Like others said, crack another window or sunroof. __________________ 2006 BMW 330i \| TiAg \| Gray - burl \| Sport \| Prem \| Steptronic \| AS
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05-04-2006, 07:16 PM	#17
David328M-Sport Brigadier General 101 Rep 3,566 Posts Drives: F30 M-Sport 328i Estoril Blue Join Date: Jun 2005 Location: Melbourne Australia iTrader: (0)	My E90 does it, my old E46 did it (still does - wherever it is now) and my old e36 did it it too. My wifes MB C180K does it as well. Nothing to worry about. I just dont have a back passenger window open without another to null out the effect. __________________ 328i M-Sport, Estoril Blue, Carbon XP 35 Tint, front heated seats, black Dakota, Sports Suspension, Anthracite Headliner, HUD, Pro Nav, Sunroof, hk 600w, Bi-Xenon, 19" 403M wheels, Reversing Camera, DAB+, Xenon, BT Ext Connect, MST turbo intake pipe, MST Cold Air Intake, JB4 on Map 2 with Catless DP produces awesome performance in Sport.
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05-04-2006, 07:34 PM	#18
Speedy E90 330 Sport, Comfort, Winter, Navi, Carbon Fiber Lip, Sparkling Graphite, Beige Leather, V710 21 Rep 155 Posts Drives: BMW E90 330 sport Join Date: Jun 2005 Location: Washington D.C., sometimes Durham, NC iTrader: (0)	Tilt open sunroof....and it will stop.
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05-04-2006, 07:58 PM	#19
Macfreak7 Private First Class 3 Rep 135 Posts Drives: E90 330i MT Join Date: Oct 2005 Location: Carlsbad iTrader: (0)	It's a safety feature. __________________
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05-04-2006, 08:10 PM	#20
nyyankee The Ultimate Posting Machine 42 Rep 419 Posts Drives: 2006 BMW 325I Join Date: Jul 2005 Location: Ft.Lauderdale iTrader: (1) Garage List 2006 325i [0.00]	Wow this exact thing happened to me today when I was driving with my sis. She thought the stero had broken...lol __________________ DISCLAIMER: Poster makes no guarantee that the above expressed information is accurate, complete, current, funny, new, spelled correctly, or grammatically correct. The above-stated information is instead provided on an "AS IS" basis, and is subject to revision with or without notice.
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