window down air effect

It has been written that, in general at highway speeds, the drag created by opening a window consumes more energy than the A/C. Supposedly, you are better off running the A/C than opening a window.

Of course, if you enjoy the feel of the wind that may be more important to you than saving a miniscule amount of gas.

 

Hi Kenmac,
I'm probably going to show my age with this post, but so what!
Back when cars had "wing windows" you could open them, and with the windows down the wind was somewhat diverted outward and you didn't get that awful modulation inside the car. I currently drive a 76 VW Beetle and if I don't open the wing windows the wind buffeting and modulating is unbearable, especially at highway speeds. Also back then when I smoked it was nice to crack open the wing window which sucked the smoke out of the car and provided a small opening to flick out the ashes.
Boy that was great to reminisce!
Good Luck with your Prius. Won't be long I'll have my White 05 #9.

cundel.....USA

 

A couple days after I got my Prius I went to a drive-thru where I had to put the window down to order. When I left I noticed my car was making this horrible pulsating sound. I thought there was something horribly wrong with the car. Then I noticed that when I put the front window down, I had hit the back window button as well and the back window was down. It scared the crap out of me.

 

Mind you, we don't have our Prius yet, but this problem seems to be endemic with vehicles having expanded compartment area at the rear (e.g., vans, SUVs, hathbacks like the Prius).

It is amazing that car designers overlook this problem. We have a Mercedes SUV that does the same thing (aggressively). The modulation is caused by the pressure surges of incoming air fighting the excess air struggling to vent. This is exemplified on some cars by the headliner flipping and flopping. A solution that often works is to keep both back windows open an inch or two whenever you are driving with the front ones open. Also, sometimes when you increase the quantity of fresh air that is fan delivered (i.e., pressurized) can help when you have a subtle imbalance.

I just don't understand why manufacturers don't design some form of 'excess positive pressure' vent at the rear of the compartment. Of course, even more ideal would be an operator control vent or window tilt opening convenience like some minivans have.

Chalk one up for the bean counters.

 

Todays cars must be very disappointing to dogs. All of ours liked to stick their heads out the windows out on the Oregon back roads.

 

I don't think Bear notices at all. He pretty much sleeps throughout any car ride.

 

I've noticed it at slower speeds - around 50-60 kmph - with only the back two windows about half-way open, on days with little or no wind. There is a very annoying resonance at that speed. Must be a standing wave set up at about 60-80 Hz. The amplitude depends on how far the windows are rolled down. I don't get it with all 4 windows open, or on very windy days Haven't tried it with other combinations yet either.

 

the '04 Prius is not unique in this respect.

The last post about air pressure trying to escape nails it. You can't bend the laws of physics.

My solution is to close all windows as I enter the freeway ramp and turn on the air or the ventilation, enjoy the filtered air, music and relative quiet.

C'mon. It's a lovely car.


Bob

 

I have also noticed the air pressure pulsating while the rear windows are open at 30-35MPH. It was unbearable, but my passenger in the right rear seat wasn't feeling well and wanted some fresh air. Opening the front windows helped somewhat. Below 25MPH, the effect was muted.

Opening the driver's window has not caused a problem.

 

You've been told human hearing only goes down to about 20Hz. Well, that pulsating is a note in the 4-5Hz range. More of a feeling than a sound. As correctly pointed out, it's a cabin resonance. I can usually make it go away by cracking open a front window.

 

Actuallly the Prius is great for dogs. With the back seats folded flat and the luggage cover removed, they can stretch out, walk around, or sit and watch the passing scenery on all sides.