Chevy Volt Wind Tunnel Video

[SuperTrooper]

Just by appearance the mirrors look like the would cause little disruption in the airflow. They are away from the body and operate in their own airflow. While their true drag may not be ZERO, it may be such a low number in comparison to the whole car that the effect it had on the electric range of the vehicle was unchanged; therefore it is neutral. They are without a doubt the most aerodynamic, usable mirrors ever seen on a "production" vehicle.

While cameras & screens are superior aerodynamically they hit 2 walls:

1. Most state laws specifically require MIRRORS and would have to be overridden by a federal law permitting cameras.

2. The last thing you want to add to an electric vehicle with limited battery range is another electric powered device. Nevermind the additonal production costs.

IMHO, a few hours in the wind tunnel has yielded the best of both worlds.

[tasdrouille]

Originally Posted by SuperTrooper

Just by appearance the mirrors look like the would cause little disruption in the airflow.

I would have thought that behind that mirror, there will be a nice wake roughly the size of the mirror itself. Just like the wake behind a hatchback. If not I would like to get an explanation why.

Originally Posted by SuperTrooper

They are away from the body and operate in their own airflow.

What is the basis of that affirmation? I don't see how you were able to determine that (that they operate in their own airflow).

[SuperTrooper]

Compare the mirror location of the Volt to the Acura on page one of this thread. The Volt mirrors are 4-5 inches away from the body and almost a foot to the rear. That is an area with good laminar flow vs the intersection of the hood, windshield and side window. Then remember in the video how Lutz explains the impotance of the air breaking cleanly away from the back end of the Volt? Same for back end the mirrors. The mirrors aren't that long for looks, it's to give the air time to acheive laminar flow so that it can break cleanly off the back of the mirror.

Again, we are probably talking about a question of scale. The point is that the mirrors have no impact on the electric range of the Volt, therefore they are "neutral".

[NeilBlanchard]

Hi,

As far as I know, small video cameras and LCD screens use pretty tiny amounts of electricity -- certainly more power could be saved with an efficient audio system, and certainly low power consumption exterior lighting, and efficient passive ventilation.

The Aptera Typ-1 uses 3 (or 4?) video cameras and screens and it gets plenty of distance out of much smaller batteries thna those that will be in the Volt. Even if you can eliminate the affect on the Cd by the miirors, you can definitely reduce the CdA by eliminating them.

[tasdrouille]

From the following image we can determine that both mirrors make up 2% of the total frontal area. No matter how well those mirrors are designed, they at least add 2% to the aerodynamic drag. Plus, there is an unknown Cd penelaty associated with the form drag of the mirror itself.

Best case scenario probably is that the volt's mirrors halve the aero drag penality over your average side mirror.

Generaly side views mirrors make up 5% of the total drag of cars. You could as well say that any average side mirror would not impact the range of the volt as the difference will probably be witin a mile.

[SuperTrooper]

Originally Posted by tasdrouille

From the following image we can determine that both mirrors make up 2% of the total frontal area. No matter how well those mirrors are designed, they at least add 2% to the aerodynamic drag. Plus, there is an unknown Cd penelaty associated with the form drag of the mirror itself.

Best case scenario probably is that the volt's mirrors halve the aero drag penality over your average side mirror.

Generaly side views mirrors make up 5% of the total drag of cars. You could as well say that any average side mirror would not impact the range of the volt as the difference will probably be witin a mile.

What you have to do first is calculate the Cd for the Volt with and without the mirrors and then factor in the area. That's what would make the actual difference so small as to be inconsequential.

Aerodynamics is more than just numbers. Shape and placement in the airstream are critical. The mirrors on the Acura are an aero nightmare compared the the Volt's.

[aerohead]

I wouldn't sell GM short on aero ability.They have constructed and competed with some of the lowest drag vehicles ever conceived.Some of their world records still stand.They have the distinction of offering the lowest drag production vehicle ever offered to the general public(EV-1/2).------------- I suspect,they suspect how ignorant the general public is about aero,and they will bring them in slow,so as not to create another Chrysler Airflow debacle.500 hours,at $20,000 a day(just for tunnel time) to refine the "stylist's" rendering is a pretty serious effort to make an accord with the troposphere.---------------------- They're capable of visionary products,lets see what they do before we condemn them.Remember,Cd 0.12 is already a reality for GM,has been since 1987,they know aero,but they've got to be able to sell aero.

[Geebee]

Originally Posted by tasdrouille

From the following image we can determine that both mirrors make up 2% of the total frontal area. No matter how well those mirrors are designed, they at least add 2% to the aerodynamic drag. Plus, there is an unknown Cd penelaty associated with the form drag of the mirror itself.

Best case scenario probably is that the volt's mirrors halve the aero drag penality over your average side mirror.

Generaly side views mirrors make up 5% of the total drag of cars. You could as well say that any average side mirror would not impact the range of the volt as the difference will probably be witin a mile.

You are wrong in that because the mirrors are 2% area wise they add 2% to the drag, if you look up any basic aerodynamics the shape is so critical to drag produced as to make area almost inconsequential to the actual drag, ie. compare a flat plate to a full aerofoil.

[tasdrouille]

Originally Posted by Geebee

You are wrong in that because the mirrors are 2% area wise they add 2% to the drag, if you look up any basic aerodynamics the shape is so critical to drag produced as to make area almost inconsequential to the actual drag, ie. compare a flat plate to a full aerofoil.

Please look up the formula for aerodynamic drag. All else being equal, 2% increase in frontal area will increase aero drag by 2%, there's no way going around that unless you believe the Cd of the car to be lower with mirrors than without.

[Blue Bomber Man]

Compare a golf ball to another ball slightly small, but without the dimples. I guarantee you that the golf ball is more aerodynamic, even though it has a larger frontal area.

If the mirrors aerodynamic qualities are better then the average of the rest of the car, than it could feasibly be that the mirror contributes less cdA then its frontal area might suggest, bringing it under the 2%