It’s a rare perfect day in Chicago, where the weather typically boils down to Snow Removal and a few weeks of Road Construction Season. Warm but not too hot, the humidity and mosquito situation are remarkably peachy as well. Driving along in your ride, you feel like you’d be ticketed for not taking advantage of this rare climate event, and you hit the DOWN button on your driver’s window.
BOOMBOOMBOOMBOOM. Ouch! It’s like a jet taking off. If your kid rolls down a back window alone it’s even worse- seems like your eardrums will rupture. Opening the sunroof adds more unpleasantness. In the twelve years I owned my previous car, I think I can count on the fingers of both hands the number of times that I had the giant glass roof open; if just wasn’t pleasant to drive. Is this just my car, or are others experiencing this?
Mass Collisions
Apparently, I’m not alone, and there’s a reason for this phenomenon. I did some quick searches for ‘Buffeting’ and ‘Buffett’, and after dismissing the many links dealing with a Boomer musician that performs to thousands of aging Tommy Bahama clad fans, I found some answers.
According to a number of sources, including The Family Handyman of all things:
The throbbing, helicopter-like sound is the outside air passing over and interacting with the contained air inside the vehicle.
When the two air masses collide, they compress and decompress repeatedly. This produces the throbbing effect. It can be as loud as a commercial aircraft.
He continues:
Many variables contribute to the effect: car shape and size, how far you lower windows down and your speed. The effect can happen when any single window is down, including the sunroof.
The helicopter sound is more pronounced when a rear window is down. This is because the side mirrors are designed to direct air flow away from the front windows. Lowering a rear window amplifies the effect.
So you aren’t imagining that the rear windows lowered alone always seems far worse. But why? More importantly, why can you roll down the side windows in a ’67 Impala and not experience this phenomenon so badly?
Good Aero Is Bad?
Well, good aero is certainly bad for windows down driving. Today almost all cars are very aerodynamically efficient, the air clinging tightly to the outside of the car.
As The Family Handyman says:
When a window opens, the air flow is disrupted, magnifying the buffeting effect. Older vehicles were designed less efficiently, and air leaked from their insides. The leaking air relieves the pressure caused by wind buffeting, reducing the effect.
Obviously, the one solution is to open another window, but that still doesn’t eliminate the problem, just reduces it. Is there a solution? Historically, there have been a few, and some from very unlikely sources.
[Editor’s Note: I actually wrote about this ten years ago (holy crap) and I asked an actual physicist, not some internet handyman. Here’s how Dr. Stephen Granade explained it to me:
That “whum whum WHUM WHUM” noise happens because the wind passing over the small window opening is like a bored drunk blowing over the neck of an empty beer bottle.
Air passing over an opening forms tiny tornadoes as it moves past the front edge of that opening. When those tornadoes, or vortices, reach the opening’s back edge, they make a wave of pressure that pushes air into and out of the car. Since sound is nothing more than waves of pressure, this makes noise. If you’re driving slowly the effect’s not too bad, but if you drive fast enough, you reach a resonant point. Imagine I stand by your open car window and use my science powers to push on the air inside the car, compressing it a bit. The car air then springs back out, then back in, then back out, then back in. With each cycle of moving out and in, the amount of air movement gets smaller until it completely dies away. But if I push on the car air again just as it finishes springing back out and is headed back in, and I do that over and over again, the amount of air movement gets a whole lot bigger and doesn’t die away. That’s what happens when you drive fast enough. The vortices keep pressing on the air in your car just at the right time to make big pressure waves that we can feel and hear.
The technical term for this effect is the Helmholtz resonance, though car people call it “side window buffeting”. Back in the 1850s, a scientist named Hermann von Helmholtz showed that the sound’s pitch depends on the size of your container of air and of the opening. The bigger the container of air, the lower the pitch. The smaller the opening, the higher the pitch. If you blow over a bottle, you get a medium-pitch whistle. Since a car’s a big container of air, you get a low throbbing noise.
So, there you go, from an actual, working physicist! – JT]
Cracks In History
If you’ve opened a sliding rear window in a pickup you know how that really helps airflow. Instead of the truck cab being a pressurized box or a big air scoop the wind has a place to escape. Even some cars had an answer for this, particularly Mercury cars from the sixties with power lowering rear backlights:
Mercury supposedly dropped the feature after air conditioning became popular, but if you’ve ever owned a black-on-black car you’d kill to be able to get the hot air flushed out of your ride this quickly and help the poor climate control do its job.
Another great solution came from what might be the oddest place imaginable: the designers and coachbuilders at the Italian firm Zagato., often makers of some of some of the most bizarre automotive creations ever (even by Italian standards). Maybe they discovered this by accident and made it a feature, but the hatchbacks of a number of their cars could be electrically raised by a switch on the dashboard. Here’s the feature on an Alfa Romeo Junior Zagato:
Or on this Lancia Fulvia Zagato. By the way, you could still open and close the hatch when is was raised since the latch itself moved:
If you scroll forward to the 15:00 point in the video below you can see it open. Like the later Stratos these Lancias make noise that hits the receptors in your brain in such a way that you want to triple the speed limit and not care about the consequences.
This Lancia Flavia Zagato might have been the first one to have the feature back in 1962.
Shit, look at that thing: if aliens really landed in Roswell and instead of being probed and killed they were put into slavery designing cars, you might imagine their creations looking something like this. Why do I want one so much?
Needless to say, I have heard that owners of these cars will get people at stoplights yelling at them YER HATCH IS OPEN BUD! Which is understandable.
The Matra Djet had a far less sophisticated way to deal with the airflow issue, almost out of necessity if you believe the remarks at around 4:30 by this somewhat familiar reviewer:
I’ve found that T-tops and targa roof cars are particularly bad in the buffeting department, except for cars like the Honda CR-X Del Sol or the Miata RF where you can roll down the rear backlight. Only one Nissan Z car I found to be reasonable with the roof panels off, and that was the disco-era 280ZX 2+2; it had remote control rear quarter windows to let out the pressure.
Our family had a later 1990 Z32 which had no such openings and was essentially undriveable at speed with the roof panels removed.
Banishing The Boom
The aftermarket has actually latched onto this idea, literally. There are numerous sources that offer a clip that Corvette owners can put onto their hatch to allow the thing to close and secure but leave a few inches of air gap to relieve the pressure of the big targa air scoop (at least on C4s).
I found a bunch of suppliers making these things so they MUST work, right? Why can’t mainstream OEM manufacturers latch onto this idea?
Once again, I’m using the Tesla Model 3 as the guinea pig of this device. Right on the switch panel for the windows would be a button to pop the glass on the hatch just enough to get air flow to run through. Of course, being a Tesla they’d probably make you go through a bunch of menus to open this thing, but let’s just apply logic anyway.
One detail- you might need to add a small mesh screen that raises with the window. My fear is the the airflow will be so good that your gas receipts and wedding invitations or whatever is on your seats might end up the street behind you without it.
Look, we all want fresh air now and then, but we want our eardrums not to bleed in the process. Do we need to buy a car with the aerodynamics of a brick to get that? I don’t think so, especially if there’s a trick we could employ to give us the best of both worlds.
The Tiny Rear Wipers On Modern Cars Are Pathetic But I Have A Solution – The Autopian
Third Brake Lights Should Be Mounted On Rear Wiper Arms – The Autopian
This Could Be A Fix For The Stupid Little Arcs So Many Rear Window Wipers Make – The Autopian
Try opening the front windows an equal amount, say 50%, and the rears a greater amount, like 75-85%. Try to achieve equal area of openness between the larger fronts and the smaller rears. I’ve found this significantly cuts down on buffeting and Helmholtz resonance, to the point where the air is almost smooth.
Getting modern windows to stop halfway is an interesting challenge, though. They only seem to want to be all up or all the way down.
Never mind windows down, I miss the old flaps down by your knees under the dashboard. You could open those and be comfortable in 100° weather.
Ah, yes, the ball coolers or coochie chillers!
“Testicools”
The Astra my family had was surprisingly comfortable for windows-down driving; some are mentioning 2-doors > 4-doors for this, but ours was a 4-door. I figure it could have been designed accordingly as not every Astra would necessarily have A/C in all global markets.
My GTI is fine enough with windows down although I rarely have windows completely down to minimize some of the buffeting, I’m usually fiddling with the windows a bit to get to find a sweet spot.
Something that I’ve always noticed is how the airflow changes when I have a moonroof open and switch recirculate on for the HVAC – seems to get a bit quieter actually IIRC. I usually think of the system as more closed and it wouldn’t have as much of an effect as it does, but then it does change the overall airflow if it’s pulling it away via the dash intake, so it’s another ‘escape.’
On the subject of pop-out vent windows, on vans – I remember Honda dropped them on the 3rd-gen Odyssey (when they added roll down sliding door windows too) which was met with some criticism. Now I don’t think any minivans have pop-out vents.
Also amusing to think of the Model 3 having a tilting rear glass but not having a tilting moonroof though.
I remember there were stickers warning of carbon monoxide in the last days of the tilt out van door back windows, that probably lead to their passing from favor.
(Laughs in 4Runner)
For a short time, we owned a 1956 Lincoln Premiere and there was ZERO buffeting with any combo of windows open. It was glorious. And vent window that could direct cool air right at your chest or lap were amazing too. I miss all 19 feet of that car.
My hatchbacks were fine with the rear windows down up to highway speeds, then either cracking the sunroof or dropping the front windows a little solved the problem. I preferred driving with the rear windows down over the front so I didn’t have the air turbulence on my face or as much noise of the wind in my ear. I figured it worked by not only allowing more air out, but the varying size of the openings breaks up the resonance affect because each opening has a different frequency and prevents the effect from getting too strong at any one of them under the normal operating speed range. With the ’86, the passenger window needs to be at least partially down to keep the buffeting tolerable beyond low in-town speeds. On the highway, with both windows down, it’s usually fine up to about 90 unless their are crosswinds, which bring the buffeting annoyance speed down
Do not have windows or sunroof open when the car is in motion. The solution is so simple. Apart from the unpleasant buffetting, open windows or sunroof totally ruin the aerodynamics.
Cars have A/C these days. Use it.
Someone here has never done any crusin’, and it shows.
Nope. I refuse your suggestion. Windows open, heat blasting, if necessary.
… Roll the window down this
Cool night air is curious
Let the whole world look in
Who cares who sees anything?…
I am here for Deftones/Maynard references.
Cool. Hop in.
Thanks for this article because it answered a burning question I’ve wondered about for like forty years. I had a 1983 Dodge Ramcharger in college with a “ram head” hood ornament the size of a toddler’s foot. Someone stole it. I was grateful. Anyway all Ramchargers of that vintage had a small, maybe twelve inch square pop-up hatch over the payload area. Now I think I know what it was for.
I just think that most modern cars are not designed to drive with the windows open. My Volvo 240 wagon has a vent on the rear quarter panel on the passenger side. It’s there to stop buffeting and increase airflow through the cabin. The car is a dream to drive with the windows open. In a wind tunnel it probably adds a tiny amount of drag, so it would never be added to a modern car. The Volvo was already a brick so that was not really a concern.
I’m the opposite: I can count on one hand the times I’ve lowered my side windows, but my sunroof is perpetually open. One thing I’ve noticed is that fabric mesh at 90*on the leading edge of the sunroof is a lot quieter than plastic at a more slippery angle.
Sunroof + sliding rear window in my truck is the ticket for airflow and noise.
I’ve never had an air buffeting issue with any 2 door car I’ve been in, only 4 door cars and SUVs.
and 4 door trucks (too late to edit my original comment)
I should have said originally ‘I’ve never had an air buffeting issue with any 2 door automobile I’ve been in, only 4 door cars, Trucks, and SUVs.’
With both windows down, my GR86 does it, but only at high highway speeds with crosswinds. With one window down, the buffeting starts a lot sooner—maybe around 50 mph—but I don’t drive with only one down, so I can’t remember at what speed I observed it. I can’t remember my S30 Zs, but in spite of their horrible aero, I think they did it, too, because copying the Zagato Lancias occurred to me after seeing one at an Italian concours. I think the Zagato Lancias most likely had better aero, so they probably had those problems sooner.
Cracking the opposite rear window has always solved this 100% for me on every car I’ve ever owned, no fancy clips or other buttons needed
With the passenger rear open at different a height so there’s no harmonic frequency.
Plus, German Shepherd in the back insists on personal open window.
Yeah I don’t like the wind messing up my hair so I crack the front right and rear left windows and that provides a nice little stream of fresh air throughout the car without a ton of noise. Sunroof can be popped open too and enjoyed this way.
I’m reminded of why we always had the rear window on the family station wagon down. I had a VW Bug with the flip out rears, which were helpful, but we also had those little vent windows in the front doors. Those seemed to help, especially if you flipped them out a ways.
Thanks to this article, I think I understand the mechanism that reduced buffeting. It was that it pushed the air away from the front door opening, while it simultaneously allowed air to be pulled from the cabin and aligned with the deflected airstream.
Maybe we could get little vent windows back in cars?
Rear window down in the wagon, rear facing seats, feat sticking out, I think it was a Rambler.
And yes, bring back vent wings.
My Ranger is damn near magical in this regard. Just roll down the window and open the rear slider and it’s breezy perfection. In most cars I’ve gotta tie up my metal mane or it will flog my face and try to blind me.
I think we need to bring back some relegated relics of the past, quarter glass vent windows. They did a great job of eliminating this problem by slightly changing the vehicle’s aerodynamics and letting air out but not in. Plus they have the added benefit of repositioning the side view mirrors to the front quarter panels ahead of the windshield, which is just cooler anyway.
Uhh…. my cars with quarter vent windows still have the mirrors in the door like usual. Is it not always like that?
Not sure. But the mirrors on my car do seem like they would get in the way if I were to fabricate my own vent windows for it.
Mine even has a separate piece of glass between the front edge of the front windows and the black corner trim at the base of the A-pillar, but yep, you guessed it, mirrors are right in the way.
Edit: What I *really* wish is that the rear side glass popped out sideways, like any number of older two-doors – BMWs were great for it at least through the E46, Volvo did it with the 242/262 (as it lost the 140’s front-door vent windows), Honda pulled it off with the fourth-gen (CB7) Accord and likely other models I don’t know off the top of my head… and of course it’s expected in a minivan’s third row.
Double edit: Ah, someone’s already mentioned those! They really do, or in my case would, help a bit.
You know that Tesla’s “solution” to boom will removing roll down windows except for a Subaru SVX style panel on the driver’s door
I literally feel it. Our 2016 Mazda CX-5 does the booming thing if a front window or only one rear window is open but with both rears partly open it’s acceptable. My 2002 F150 Super Cab is fine with the windows open since the rear quarter windows flip out and I have a rear slider.
Even 67 Chevys have this issue. I have one. If you open a window it buffets. If you open just the kick panel vents it builds up pressure and is noisy. The trick is to open the kick panel vents all the way and slightly crack the front windows. This is nirvana where you get a nice steady flow of cooling air and no buffetting. I drive like this in the 2 months of the year I don’t need to run the AC here in Florida.
Kickpanel vents rock! I had those in my non-AC -65 Buick, and they were a gamechanger to warm day driving. Those and vent windows should came back!
The Mercury breezeway was wonderful even in California’s Central Valley.
Also the soft window Porsche 911 and 912 targa with the top on but the rear window zipped open.
My 50 year old 2-door Corolla has rear windows that pop open just slightly, like those in 80’s and 90’s minivans. The car doesn’t suffer from buffeting that much, but when it happens, simply opening the rear windows relieves all of the pressure.
I was sad when those popout rear windows disappeared, as it was such a elegantly simple solution to better ventilation.
Really? I always thought those were pretty pointless. They made a very marginal contribution to airflow through the car in my experience
I had friends who had Escorts and (go ahead and laugh!) a Pontiac Lemans, and they seemed to improve the airflow, esp if you where sitting in the backseat.
The RX-8 had those in the small windows in the rear doors, and they make an appreciable difference. That car is also small enough that I can reach them all from the drivers seat, despite having 4 reasonable sized seats
I wish like hell my Yaris had those, because I bet they’d make a meaningful difference.
I thought Tesla had a feature to pop the skylight, even the ones that were not supposed to open?
“Opening the sunroof adds more unpleasantness.”
I also gave up using the sunroof and never again got a car with one.
Yeah, the only cars I’ve had with sunroof had them because they were already sitting on the lot that way, I’d never order one special. Only times I opened them was when I felt obligated to use them once in awhile because it was there, but never cared for it
Sunroofs suck
The 300 SL Gullwing has two vents above the rear window to allow air to escape. Why not something like that, with active shutters?
Or just drive with doors open, because the windows don’t open.
That was their solution for an oppressively closed cockpit with poor ventilation. They didn’t have flow through back then. Effectively, that’s what a sunroof in tilt mode does, so it’s already widely available for a lot of cars. It doesn’t stop the effect, but it does work to move the onset up to a higher speed.
In my experience -and I drive a lot of different new cars – this all depends on the manufacturer. In BMW’s, I can drive highway speeds with an open sunroof without any problems. In Volkswagen-products, from Polo to Panamera, it all sucks. Window open=catastrofic buffeting, as if by design.
Why wouldnt opening the hvac vents to allow outside air to diffuse the wop wop wop?
You want air to escape, not air to come into the cabin and add more pressure. What you say would make sense if you had an HVAC system that pulled air out of the cabin, not in.
The volume of air is too low. I would think it would need to be able to positively pressurize the cabin at all times to push the onset of the buffeting up to a higher speed than would be reached. Otherwise, you want to pull it out, which flow through ventilation does, but at too low a volume as it’s a small rather convoluted exit path that’s passive, relying on a low pressure zone at the rear of the car to extract cabin air.
That is NOT a 67 Malibu ????
It’s either a 64(debut) or 65.
CatManDue- HOW DID I NOT SEE THAT? No wraparound taillights, no tapering C pillar. My uncle had three-on-the-tree V8 ’64 so I flat out should know better. Sorry!!
Ownership of one’s mistakes only enhances one’s overall credibility.
Good on you
My first car was a 66 so that sentence was the equivalent of walking into a brick wall hah