Windows vibrate on Prius
Created September 15, 2005, at 2:57 pm by Anonymous
Has anybody experience what I'm about to describe on the 05 Prius? I notice that my back windows vibrate when I open them up half way. It doesn't sound like just the wind but rather a vibrating noise like a helicopter was flying above. Has anyone with an 04 or 05 Prius notice this?
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I don't tend to open the windows and drive, if that is what you are referring to, because with even "conventional" cars, open windows is less efficient than using air conditioning (particulary at 45 mph up), and besides I can't stand the buffeting noise anyhow! The reason that air conditioning is more efficient than open windows is open windows makes for aerodynamic drag, using more fuel than would the air conditioning (which is of course electric on the Prius, but still utlimately uses fuel).
Therefore my suggestion would be to not leave the windows open while driving. In the hyper-aerodynamic Prius (I also have an '05 Prius), I would be willing to bet that it would be more efficient to use air conditioning at anything over say 30 miles per hour. I do open the windows when I'm sitting at a store waiting on the little old ladies I take home from church to do their weekly shopping, or similar situations - but then the car is static, and of course it only makes sense to do this when the outside temp is in the low 70's and no higher.
While riding as a passenger in an '04 Prius I experienced the same thing, and have the same thing happen in my '04 PT Cruiser.
In both cases, it is actually the rear hatch and/or roof that shudder, due to air pressure oscillations. When the windows are open, air is rammed into the rear of the car with no outlet, which causes severe pressure changes, and indeed increases drag on the vehicle.
If you really want to drive with windows down, try leaving one or two windows higher up on one side.
I suspect that this is a common thing to have happen with most cars that have air conditioning. Also, today's cars are built with thin sheet metal, which vibrates easily. Again, they are designed to have external airflow across the roof and along the sides, not to have airflow into the passenger compartment and out again through the back of the car.
Thanks fellas...I know that opening window is not efficient on gas mileage but what I was trying to do was to slow the car down because I was going down a steep hill. I know its not the best way to slow a car down but I was hoping it would cause a bit of a drag so I would slow down. And as I did that I happen to notice the strange vibration of my windows that I haven't ever experienced in any other car. Not that It cannot happen in other cars either so I'm just wondering if anyone has experience the same and whether this is a problem? Perhaps its a Prius design problem?
I'm not wondering about my MPG or whats better for fuel efficiency here.
I've noticed the same harmonic vibration too on my 2005 Prius. I don't think it is just the windows, but rather several parts vibrating together. I have also noticed that it only happens when the rear windows are open and the front windows are still shut. If you open the front windows a little, the vibration will go away.
As one of the previous posters mentioned, it is probably more efficient to leave the windows shut at speeds above 30 mph or so.
A friend of mine who worked at the GM wind tunnel in the 80s told me that, even back then (the 'olden' days), at highway speeds, it was more efficient to run the A/C than to have one window open all the way.
Hi, Yudah... To assist in slowing a Prius when going downhill, shift to the "B" positon, designed for that purpose. This in adequately explained in the Owner's Manual.
Charles,
Thanks...I know what the "B" does now but this was before I knew what it did. Your right in that just use the "B" gear for going downhill. Works great in fact, I use it all the time now, however. My point here is not about gas efficiency, better MPG, turning on AC, or using the "B" gear...its about whether this vibrating thing is a problem in the Prius design?
My 2004 Prius doesn't have any window or hatch vibrations, but it has an unbelievable amount of rattles. There are rattles in both front doors, the rear-view mirror, and the back seat latch. They are totally intermittent, so trying to get them repaired by the dealership under warranty has been frustrtating since they seem to go away when I bring it in to get checked out.
Hi,
Remember Toyota made Prius to
act as a 'normal' car...
Doe not expect anything special
outside your THSD
Even your creeping up with your
foot off the break
is programmed!
It is just a very fuel efficient car..
Have fun like I have
with Prius II
The same sort of resonance occurred to me today when driving my new 06 Prius. Back windows down about halfway, going 30-40, front windows closed. Was turning the AC off and opening the back windows when I was overwhelmed by a very loud, scary-sounding resonance. Thought something had gone wrong with the car at first, but a little experimenting showed that it was a vibration-based, very loud noise due to a certain back window configuration.
it has to do with the aerodynamics of the car. it is nothing vibrating. it is the high speed wind fighting itself. if you open another window in the front, the wind has somewhere to go and the noise stops.
This "resonance" / "vibration" is called a "Karman Vortex" (named after the same aerodynamicist who designed the Karman Ghia, by the way). It's the back-and-forth buffeting you feel when you drive too close behind a big truck; the same effect causes a flag to ripple in the wind. See http://www.everything2.com/index.pl?node_id=922954 for a short discussion; and http://www2.mech.kth.se/~yuan/CFD05/Presentation_files/image001.gif for a picture.
Has anyone gotten the dash rattles that seems common on Prius' fixed permanently? We've had our '07 Prius in the shop 3 times already to try to fix the same passanger-side dash rattle. I just brought it home yesterday and this morning heard the rattle again! I'm losing hope.
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