GM describes 2013 Chevy Malibu ECO aerodynamic tweaks (Cd ~0.28)
 

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Detail optimization removed 60 counts (0.006) from the drag coefficient, making the shape "nearly as efficient" as the Chevrolet Volt .28 Cd.

Some of the improvements, quantified:

Those are 28 counts of the total, all of which result in "up to 2.5 miles per gallon more on the highway."

(NOTE: see post #18 for the rest of the modifications, quantified.)

A quote about working within government regs:

Source: Chevrolet News - United States - News

Should I be rewarding slow, incremental improvements by regurgitating corporate press release tidbits about cars that "almost" get to .28 Cd?

I feel kind of dirty. :D

Don't feel dirty. This looks a lot better than the frumpy American sedans of the 90s that drove people to SUVs

MetroMPG -

One mm at a time? I'll stick with one M&M at a time.

CarloSW2

...as the beggar said: "...well, I'm ALMOST rich..."

...l'd like to *see* those 1mm adjustments! Made with a sledge hammer on the metal stamped body panels?

Well, I've been as hard or harder than most on GM, and particular their use of numbers, but lets give them a little credit when due. It is a decent looking car and they are actually concentrating on some of the important aero details. Hucho made the point, in fact an entire chapter, on how attention to details could add up. If I had a family of five and needed a soft riding long trip car, I'd consider it.

yes Please!
 

Darin,it's all a move towards greater knowledge.I appreciate the ears to the rails big-time! Thanks!

Good point. When EcoModder was new, I recall seeing more than a couple of threads on traditional "enthusiast" forums along the lines of how crazy we (EcoModders) were to be partially -- or mostly -- blocking our grilles, for example.

With companies like GM, Ford, BMW and others now doing this as original equipment on some production cars, that blather has subsided.

Educating the masses.

I'd go for Hershey Kisses, but whatever floats your boat (in the most hydrodynamically efficient manner)!

Can't help thinking the wheelarch "ears" are NOT helping !

Sorry to be cynical here but .28 is not all that good.

Citroen managed .29 in 1974...also on a 4 door , 5 seater production sedan ;the CX model.
The original version had .30 but later variants had .28 / .29 depending on equipment and specs etc.

Panel fit was somewhat umm... variable (yes we'll call it that to be kind) and there were gaps you could put your fingers through (between the headlight and the bumper for example) so some "tweaking" should be able to drop the numbers even further.

Peter.

i wonder how usefull drag coeficients really are for comparison ....
i assume that with more accurate testing these days...such as spinning wheels, etc, drag coeficient would come out higher, because more detailed testing will reveil more drag.
i've heard they're also dependant on the actual wind tunnel used.

so how comparable are drag coeficients of something that was tested 20 years ago in a different wind tunnel with something tested today. or two current cars tested in different wind tunnels, wich they very likely will be if they're different brands.

that said, the lower is obviously the better, and 0.28 is not something to brag about... the opel insignina/buick regal is build on the same platform ...the the ecoflex has a claimed 0.26Cd!

than again drag coeficient seems very dependent on things like tire width and engine choise, different (bigger)engines needing more cooling = less factory grill blocking
this combined easily changes the Cd by 0.02, without any visible external changes.

the good thing in all this is aerodynamics is back in the marketing talk...

Hi lunarhighway,
Before 1974 there were no full size automotive wind tunnels. Before then and still today published drag figures for real cars are derived from coast down tests. The drag numbers should be exactly comparable. Some prototype work publishes drag numbers based on wind tunnel tests on models.
-mort

usefull
 

I'd like to see them listed on the new car window sticker along with the frontal area.
It would be to the consumer,as square footage and thermal insulation ratings would be for a home.
The Cd would be the equivalent of the heat transfer coefficient of the home which is the inverse of its composite R-Factor.
And the frontal area would suggest the CFM/CMM in which your going to push that R-Factor.
Driving speed would be the same as design indoor temp..

Why does the "face" of the new Malibu remind me of a transformer... ? Anyway: what manufacturers forget to mention is the frontal area? SUVs now can have drag coefficients in the sub-0.30 range if I'm not mistaken. Everything helps, but as mentioned above, .29 is not THAT great.

aerohead -

110% agreement. Published info like that should also increase the competition to have better numbers.

CarloSW2

[QUOTE=mort;256699]Hi lunarhighway,
Before 1974 there were no full size automotive wind tunnels. Before then and still today published drag figures for real cars are derived from coast down tests. The drag numbers should be exactly comparable. Some prototype work publishes drag numbers based on wind tunnel tests on models.
-mort[/Q


Sorry but not so.

The St Cyr wind tunnel in Paris was in use in the 1920's and is still used today especially by Citroen and Peugeot.

Coast down tests are probably still used by some makers but most have moved on the CFD and wind tunnel data.

German universities also had auto wind tunnels in the 1930's to help with the aero work on the Audi and Mercedes cars of the mid and late 1930's (usually referred to as Silver Arrows)

Peter.

Hi Peter,
I think you misunderstood. I meant that the lift and drag numbers before 1974 were from wind tunnels that were built to study airfoils or aircraft. The only 1:1 scale automotive tunnel before the oil embargo was the GM Harrison tunnel used to test cooling system flow. Since that time really wonderful study centers have sprung up all over.
But in particular, the Saint Cyr "giant" tunnel of 1920 was not an automotive type tunnel. The test object was suspended by 5 wires and the forces on the wires gave you the lift and drag. I think the nozzle exit area was about 4 or 5 sq meters. Which would be about 1:5 scale for an automobile.

I see aerohead posted this.

The EPA uses coast down tests for drag measurements. Advertising can, of course, use any numbers they like.
-mort

More quantified info about the Malibu's aero tweaks, and how many counts of drag (0.001) each contributed:

Also noteworthy about those grille shutters, something I'd been wondering about up here in the Great White North: seems we automatically lose the aero benefit during the winter...

Source: 2013 Chevrolet Malibu is No Drag in Aerodynamics - MarketWatch

very interesting numbers, i'm surprised at the effect of tire deflectors, because if the numbers are right than that would mean small plastic rectangles in front of the tires have as big an effect as smoothing out the entire underside of the car? no wonder just about every new car has them.

how well would these numbers transelate to other cars i wonder..., because assuming these mods would have a similar effect on my car i might have gone from a stock 0.29 to 0.263 and i might go to 0.256 when my actuated grill block is done... i very much want to believe this is true, and the way the car coasts certainly makes it possible to imagine.