Driving 45mph with rear windows down - what a terrible aero

[goixiz]

I have driven many cars and this has been the worst with the rear windows down (one or both)[Front windows both UP/close]. The resonance from the wind driving at 45+ mph was unbearable and i had to wind up both the windows immediately. The outside was calm (wind no more than 1-2 mph, dont recall the direction) and i dont think it matters since it as so bad.

Has anyone experienced this ?

 

[aarond12]

What you're experiencing (buffetting) is because of GOOD aero. It's due to the laminar flow of the air over the sides of the car, splitting and entering the car until the pressure equalizes, repeated over and over.

Think of blowing over the open top of a bottle. That sound is exactly the same thing that happens in your LEAF, except at a much lower frequency (due to the larger size the air must fill).

To solve this problem, give the air somewhere to escape. For most vehicles, that means lowering the front windows a bit and possibly raising the rears too. If you're really interested in solving this, try putting some sort of diffuser on the B pillar. While this will cause some aerodynamic drag, it could help reduce buffetting.

 

[johnrhansen]

Wouldn't it be better to leave the windows up and run the ac? I bet your net battery drain would go down.

 

[DaveinOlyWA]

I have driven many cars and this has been the worst with the rear windows down (one or both)[Front windows both UP/close]. The resonance from the wind driving at 45+ mph was unbearable and i had to wind up both the windows immediately. The outside was calm (wind no more than 1-2 mph, dont recall the direction) and i dont think it matters since it as so bad.

Has anyone experienced this ?

this is a well known effect and is present on any aerodynamically "efficient" car. first experienced this in my Prius. I actually thought it would blow out my ear drums.

 

[OrientExpress]

It's called the Helmholtz resonance Helmholtz resonance

 

[goixiz]

Wouldn't it be better to leave the windows up and run the ac? I bet your net battery drain would go down.

This has nothing to do with battery drain nor efficiency. When i feel like driving with windows down i just do it. I dont drive ECO mode nor try to get high miles/kwh or add more trees in wings,......

 

[DaveinOlyWA]

Wouldn't it be better to leave the windows up and run the ac? I bet your net battery drain would go down.

This has nothing to do with battery drain nor efficiency. When i feel like driving with windows down i just do it. I dont drive ECO mode nor try to get high miles/kwh or add more trees in wings,......

+1. I also prefer the windows down option and is almost always what I choose at street speeds. it has to be in the upper 80's or more (rare here. we average 5 days a year in the 90's) before I will consider A/C over windows. on the freeway, its a different story. even when stuck in traffic, its A/C. too much noise and exhaust to deal with then :x

 

[johnrhansen]

To each his own. The only times I open my windows is when I crack them when im parked or if I have to pay a toll. Even at 25, it's too noisy and stinky for me.

 

[uglyduck]

Wouldn't it be better to leave the windows up and run the ac? I bet your net battery drain would go down.

If that is a fact, then I'll start turning on the AC. I've been leaving 'em all cracked 2 inches assuming that its the most efficient compromise between aero & comfort. Hasn't been hot yet this close to the coast in wine country.... but I'll close 'em up & run the AC if its easier on the battery....

 

[johnrhansen]

Wouldn't it be better to leave the windows up and run the ac? I bet your net battery drain would go down.

If that is a fact, then I'll start turning on the AC. I've been leaving 'em all cracked 2 inches assuming that its the most efficient compromise between aero & comfort. Hasn't been hot yet this close to the coast in wine country.... but I'll close 'em up & run the AC if its easier on the battery....

I

I drove 110 miles on a charge once. With the ac on. The power draw is negligible almost. Yeah it does draw some power, but it doesn't take much aerodynamic drag to cancel that savings out.

 

[DaveinOlyWA]

if you have a 2013 or later, you can run air with A/C off which is what I do in the morning. its very refreshing and uses no more power than the fan

 

[goixiz]

If the aero is so good for the LEaf why is it that it does not happen when only the front windows are down.

End of the day
if i want the rear windows down when i drive, its not tolerable - end of story
if i have to do some thing to avoid this situation (common scenario) then some one didnt do their job. Because this is a commercial product, and im sure we paid for using this product.

p.s. no complaints if this is a free loaner.

 

[aarond12]

If the aero is so good for the LEaf why is it that it does not happen when only the front windows are down.

You must be a troll. You won't even open the front windows a little bit to eliminate the buffeting? Quit whining.

Go drive a Prius or any other modern, aerodynamically-styled vehicle and you'll have the same experience.

 

[Nubo]

If the aero is so good for the LEaf why is it that it does not happen when only the front windows are down.

Because the airflow is not quite laminar near the leading edge of the front window. There's this large thing called a windshield disturbing the airflow.

End of the day
if i want the rear windows down when i drive, its not tolerable - end of story
if i have to do some thing to avoid this situation (common scenario) then some one didnt do their job. Because this is a commercial product, and im sure we paid for using this product.

They could "design out" the problem by making the car less efficient. But we paid money for it to be efficient. Or, maybe with a very large speaker controlled to cancel the resonance frequency. Or ducting to equalize pressure (regardless of outside air temp?). None of these seem preferable to simply pressing a button to lower a front window a couple of inches, seeing as how you already wanted outside airflow.

 

[goixiz]

If the aero is so good for the LEaf why is it that it does not happen when only the front windows are down.

You must be a troll. You won't even open the front windows a little bit to eliminate the buffeting? Quit whining.

Go drive a Prius or any other modern, aerodynamically-styled vehicle and you'll have the same experience.

Thank you for your most valuable comment. Do you have anything valuable to add?

 

[Levenkay]

Empirically, rolling down diagonally opposing windows seems to help, although I don't usually roll them down more than three or four inches or so