Do Rear Spoilers / Wings Help Any?
 

No spam meant, but on this subject I did find a great website to have spoilers purchased, maybe installed on cars:

Car Spoilers including Rear Spoilers and Car Wings - Rear Wings and truck spoilers

Ok, I have an album of pictures showing my 2009 Chevy Cobalt LS Coupe XFE on file with my profile here that shows my spoiler clearly.

http://ecomodder.com/forum/member-ja...68-resize1.jpg

I bought the car out right after getting an insurance settlement for a very bad wreck I had, due to my brakes not working and almost getting me killed around a curve. I also got about $5,000 in discounts from GM, my father a GM Retiree, and the dealer that had my car on their lot. I must admit it is a strange feeling having a brand new car with no payments. And my insurance company did not wish to raise my rates nor drop me due to the conditions of the wreck- they did not seem to fault me. (it was my only wreck in my life, and I'm 44) But I was driving a med size 4X4 Chevy Colorado pickup truck that got around 17MPG (20 EPA)- this was rated BEFORE THE EPA REVISED THEIR METHODS OF SCORING MPG ON CARS/TRUCKS. I next got a sub-compact with EPA of 37 Highway 44 possible (as read on sticker on the window). What I am now experiencing is like culture shock. I can now drive to places on a gallon of gas that used to cost me over double that. I feel as if I have been freed from the chains of High Oil because of the vast improvement in mileage.

Back to the topic on hand:

I tried my best to find a Cobalt that had only 4 important requirements:

#1) It HAD to be an XFE
#2) I wanted the color RED (Because Chevy's "Blue" was far too dark for my tastes)
#3) The car HAD to have a rear spoiler.
#4) Spare Tire ($75 for the "doughnut")

The car was no longer in production for 2009, and the team was on break. So I had to pick from the car lots near my home state because XFEs were very rare, and I had no transportation and could not afford to wait months. I was working with a sales-guy and a dealership that I fully trusted due to all of the business my father had gave them over many years. I had many bad experiences with sales people treated me rudely or making assumptions that were false about me, so I was sticking with the dealership I was at. Finally my guy found a car fitting my description, only it also had the $40 option of an ashtray which was only a large ashtray shaped like a cup for the cup holder and a lighter plug for the socket (shesh)- So the car was strip down to standard options except for the ashtray and lighter (which I did not need and gave away), spare tire and jack and the almighty rear SPOILER. It does have many standard features that impressed me, yet things one takes for granted as being standard were not. It does have an awesome stereo system in it that was standard, and that means a lot to a guy that plays music such as myself.

http://ecomodder.com/forum/member-ja...re-place-i.jpg
The rear of my car reminds my a little bit of a 1985 Pontiac Fiero GT I once owned that had a spoiler on the rear. Or even a tiny bit like the back of a Corvette. I really likes the looks of a Cobalt Coupe better with the spoiler mounted, (the 2009 Sedan is another story), but I do not expect it helps my MPG any....

So, what do our EXPERTS here think? Generally speaking, or at least with a car like mine, do these stock mounted spoilers help the fuel efficiency even a little bit, or are they just for looks? Could they maybe HURT the mileage some because they are not as high up as real sports cars often have? - And there lays my beef: It seems like on the real expensive sports car, be they street legal or otherwise, their rear wing is normally mounted much higher than on stock cars like mine being sold.

I assume the rear spoiler on my car is at best good for looks, and at worse, it might even be a drag on efficiency.

Experts? (all please weigh in)

Thanks. :thumbup:

See the mods and tips at the top of the page? Good read, fun and educational.

In general, a wing is good for traction and bad for economy. Because the racy image sells so many cars, wing-like things are sometimes used to help cure separated airflow over a rear window, which is good, but not as good as a plain fastback.

Interesting. I was afraid that such a device might make the mileage worse.

Frank: Thanks for the tip. I had overlooked the Tips posted here. :rolleyes: "my bad"

Still ' would like to learn about more thoughts on this subject.

Peace.

Many efficient cars that have "spoilers" really just have deck lid lips/extensions to encourage flow off the trunk to separate cleanly, rather than curving partway down the rear of the car before separating (which increases both lift and drag).

So here's my GUESS: IF your trunk (without a spoiler) has attached flow at its end (and I'm guessing it does), and also a relatively sharp corner in the metalwork transition to the back of the car (no idea), then that raised spoiler probably hurts since it would increase the size of the trailing wake.

But that's only a guess. And unfortunately, I bet the difference would be small enough to be hard to detect in coastdown testing. But you could always try. That would give you a definitive answer.

a quick google revieled an article claiming an 0.32 Cd for both the sedan and the coupe, seems high for the coupe as the cobalt is esentially the emerican equivalent of the opel astra G (same platform differnt body) the astra coupe has an 0.28Cd without a spoiler where the sedan has a 0.29.

the chevy seems to sit a little higher off the ground than the opel (possible softer american suspention vs the astra's hard euro setup?) and with FE not being so important for this type of car in the US (as you say yourself you doubled your milage with this car so chevrolet doesn't need to squeeze every last mpg out of it)

i think the spoiler might add 0.02 or so to the Cd, just a guess though....

loosing the spoiler is possibly the best for FE...beause "real" spoiler are only there to allow for extremely fast cornering wich doesn't matches well with FE driving anyway

than again, if you like it... just drive carefully with FE in mind and you should see a very decent milage on that car anyway

Jammer -

I'd look into Bonneville Salt Flat cobalts for spoiler inspiration :

Top - 2006 Chevrolet at the Bonneville Salt Flats
http://www.seriouswheels.com/pics-20...e-1280x960.jpg
If I hade a coupe or sedan I'd spend more time researching this design. However, I can't say that this spoiler has any benefits. It could be for downforce or it could be to "mask" the parachute from the airstream. I just don't know.

CarloSW2

Carlos - Downforce. They use them in NHRA/IHRA as well.

I don't remember the whole reason they work, but I think I remember something about Bernoulli in there, or maybe I was day dreaming during that lecture. Either way, they're there to produce downforce.

OP - Check out the '99ish Pontiac Bonneville - that spoiler is for better aero, definitely. If it weren't there, the flow would curve sharply around the deck lid at the rear, funneling toward the center due to the overall shape of the deck area. It would be bad.

The spoiler, however, is probably neutrally helpful compared to the bare deck lid, since it's tilted up and it's a wierd shape/angle that I'm sure doesn't do much for aero at all.

The rear of the car seems almost perfect for aero from the rear windshield down, visually... it's not , but it seems that it is... if only they hadn't curved the deck lid like they did.

I say: Take it off and use the mounting holes to secure a Kammback... :)

If you want to know if it's good or bad, that sounds like secure reasoning for TUFT TESTING! :)

If you are concerned about aero, it sure wouldn't hurt to lose that huge antenna on your roof ;)

http://ecomodder.com/forum/member-ja...han-i-have.jpg
Sorry that CB Radio is mighty powerful, and the antenna is a class leader and made of copper with a silver coating. My test so far show NO difference in my mileage with it on or off. It's like a knife when I drive, it cuts through the wind and bends backwards. To me such a sight is beautiful! In these parts a CB radio is almost as common as a cell phone when on the interstate. I can be herd 20 miles away with my system through mountains, but before I had it worked on I could only get out about a mile because these mountains stop your signal from going very far. It's the next best thing to On Star and a Cell Phone WITHOUT THE MONTHLY BILL! ALL DRIVERS SHOULD HAVE ONE.

I could write a book on the CB slang and all the advantages on using one on long drives. Cell phones are nice, but you normally can not just pick it up and talk to the driver that just went past you. The CB is like part of me.:thumbup:

Also I think it helps the local police recognize me. haha.. I'm the only Cobalt XFE in this county as far as I know, AND after dark I drive in EOC often, with a bright GPS, a Valentine One radar direction detector, Supped up CB Radio with the obvious 7 foot antenna on top. Some people see me in their mirrors and slow down (guess I must be a cop, eh?) and when police are behind me they don't follow me for very long any more. I honestly think they know exactly where I live, my age and everything. And I think their target are young twenty-somethings going to the big school here that are partying and driving, so they sometimes seem to think I'm a kid but they seem to recognize my gear on.in the car and normally they just move on looking for the trouble maker they originally thought I was. It's a small city I live near, it does not take long to recognize who drives what. But I just have to laugh sometimes because I'm sure the police sitting in speed traps must get a laugh out of my tiny car with the 7 foot antenna every time they see it. Once I had a cop directly behind me on my bumper in a good mood see my fancy radar detector and he started turning on his radar gun on and off until I see him in the mirror and he grinned and flashed his brights at me. I guess there ok in my book, and the state boys can be reached on a cb just as fast as a cell phone here often times, I have had to do it before! lol

New Photo. Read about it below picture.
http://i219.photobucket.com/albums/c...NT_ICE_VG4.jpg
A detailed picture of the wing from the rear.
This picture also shows my entire "7 foot tall Roof Mounted Night Time Bat-Killer" :D
(After dark my cb antenna has been known to hit flying bats)

Hey! Bats eat skeeters! You be nice! :mad:

As far as I can tell they run into ME first. Kind of like the Deer when they panic and run straight at your car because they are blinded by the headlights.

Hey, these critters are GREAT for farmers with large gardens, they eat anything that eats your garden AND I'm pretty sure they eat Skeeters too! Some farmers buy their eggs by the thousands on the internet so they can stay organic and not need any pesticide.

http://i219.photobucket.com/albums/c...g?t=1254539177
Wanna talk about GREEN? Praying Mantises RULE!

Christ -

Ok, I'm gonna keep that in mind from now on. On the small chance that a "restrained' version of the spoiler might be helpful, I made a 10 degree ideal angle assumption in this picture :

http://ecomodder.com/forum/member-cf...-spoiler-1.jpg

But I also agree that the Cobalt already has a nice rear-window slope. Very Nissan 240SX-ish :

http://ecomodder.com/forum/member-cf...ssan-240sx.jpg

CarloSW2

Carlos - lower the front of the Cobalt 2 inches, and you get a lower angle for the rear airflow to achieve... I believe it would drop so that the natural edge of the decklid would be at or near that 10* point.

Christ -

Oooooh, lots of combos here :

1 - Lower the front by 2 inches.
2 - Lower the front by 1 inch and raise the rear by 1 inch.
3 - Reduce the diameter of the front wheels by 1 inch and increase the diameter of the rear wheels by 1 inch. You'd get the 2 inch net and you could *claim* you were going for a classic race car look.

The first is the probably the best, but there's room for more choices.

CarloSW2

Do ALL that, then...

Really jack up the rear, paint the rear suspension pieces bright orange, and voila!~ the late '70s look! :p

Doing the highlighted option would only get you 1/2" lowering in the front, and 1/2" raise in the rear. You'd need to double your lift/lower in tire diameter to net the same gain as altering the suspension.

I'm sure you know that, but I'd like to make it clear for others.

(Increasing the Radius by the same number as a suspension mod would create the same overall lift/lower, but the diameter is R2, which is to say that R = 0.5*D.)

Land speed racing is a whole different animal than drag racing. That spoiler is undoubtedly designed to reduce drag as well as reduce lift. At Bonneville, reducing Cd is the number one goal of body design. Often ballast will be added instead of spoilers to add downforce for traction since you have a long distance to get up to your top speed.

I've got a book called Competition Car Aerodynamics that discusses the effect of angle and spoiler length in some detail. According to it, on a typical stock bodied car, a spoiler with an angle less than 20° can both reduce lift and reduce drag.

Mike

help?
 

without endplates it's already been emasculated by GM.It's not large enough to effect much change even if it was "complete",and without the car or a set of blueprints for the car, it would be hard to calculate anything.---------- If it were mine I'd keep it.If I were going to investigate drag reduction in that region of the car,I suspect the final spoiler would be quite different.

awesome book, even if its more related to racing, some of the stuff in it can still help here

I'm betting it's used to help kill some lift , without increasing the drag , or both could happen , lift induced drag, since the car is wing shaped,

revisiting the Cobalt EcoTec Land Speed Spoiler
 

I've been wrapping up noodling on the HOT ROD Magazine Camaro Red Hat Project LSR, Ford Fusion 999 Hydrogen LSR , and Volkswagen Jetta Hybrid LSR cars.
* All used wiper delete
* All used mirror delete
* All were lowered
* All used narrow GOOD YEAR EAGLE racing tires
* All used the MOON Equipment, full, convex wheel covers
* Two of three used 100% grille blocks ( Jetta did not )
* Two of three used 100% belly pans ( Jetta did not )
* two of three used rear spoilers ( Jetta did not )
* All cars were allowed a 5.3% frontal area reduction ( mirrors, lowering, narrow tires)
* The apparent departure angle, from backlight-to- spoiler top, happen to match the streamlined 2013 template contour for the Camaro and Fusion
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* The Camaro went from Cd 0.467 to Cd 0.20
* The Fusion went from Cd 0.34 to Cd 0.21
* The Jetta went from Cd 0.28 to an estimated Cd 0.2706 ( reverse-engineered from Volkswagen data )
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* The Cobalt sedan SS, with high-mount rear 'wing' is published @ Cd 0.324
( I've seen no other reported Cds for the Cobalt
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* The Cobalt EcoTec LSR car used wiper delete
* The Cobalt used mirror delete
* The Cobalt is lowered
* The Cobalt used narrow GOOD YEAR EAGLE racing tires
* The Cobalt used the MOON wheel covers
* The Cobalt used a 100% grille block, except for a combustion-air inlet at the forward stagnation point
* The Cobalt used a 10-inch rear decklid extension spoiler identical to that of the Fusion
* The Cobalt would have been allowed the 5.3% frontal area reduction
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I've yet to find a 'blueprint' for the Cobalt.
Should I do so, and find that it also matches the same contour, the implication for me is that the Bonneville spoiler allows:
* altering the basic vehicle configuration to generate negative lift ( W.H. Hucho, page 281, 2nd-Edition)
* ' Additional force is obtained by positioning the rear positive pressure far back behind the rear axle... thereby producing a greater leverage about the center of gravity.' ( Hucho, page 282-3, 2nd-Edition )
* ' The attached spoiler ... provide(s) nearly the same drag and lift coefficients as raising the upper rear edge ( of the body ) [ Hucho, page 175, 2nd-Edition ]
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The spoiler constrains the flow, forcing it to follow a streamlined pathway, facilitating flow attachment, flow deceleration, pressure recovery, increased base pressure, pressure drag reduction, reduction of rear lift, and providing a robust flow environment for pilot-chute inflation/ main parachute deployment.
It's not as 'good' as just streamlined shaping of the car, but it does satisfy SCTA Rulebook body modification limitations.

cursory look at Cobalt
 

*I printed off a blueprint of the coupe and sized it to fit my contours.
* The sedan and coupe are identical in both width and height.
* They're within a fraction of an inch in length.
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* Without the rear wing, the upper trailing edge of the deck is a match for the 2013 template.
* I've no idea whether the SS high-mounted spoiler is decorative, intended for direct downforce, nor whether it reduces, or increases drag.
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* The only Cd available for the Cobalt is for the 4-door sedan SS, at 0.324.
* This SS also has 1-inch extensions to the rocker panels and both fascias.
* There is no brake-horsepower/drag-limited top speed data available for the car.

Cobalt estimates from blueprint
 

Using available photographs of the ECOTEC LSR car, I modified the technical drawing, lowering the car, and adding the SCTA-spec rear spoiler with 'spill' plates ( as they refer to capping plates ).
Estimated race car dimensions:
Length- 185.59-inches ( 4714 mm )
Width- 67.91-inches ( 1724.91 mm ) published
Height- 53.21-inches ( 1351.53 mm )
Body height- 49.116-inches ( 1247.54 mm )
Forebody- 54.22% of total length
Aft-body - 45.77%
Ground clearance- 1.00-inch ( 25.4 mm )
Verjungungsverhaltnis- 1.7296
L/H- 3.48787
L/h- 3.7786
L/W- 2.7328
( Long-tail length )- 261.42-inches ( 6640 mm )
L/ square-root of Af = 3.2329
Estimated coefficient of aerodynamic drag- 0.21
Estimated frontal projected area- 22.885-sq-ft ( 2.126 meters-squared )
Estimated CdA- 4.8058 sq-ft ( 0.4464 meters-squared )
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*The OEM Cobalt backlight base slant angle is 19-degrees
*The deck relaxes the backlight-to- trailing edge exit angle to 12-degrees, intercepting the 2013 template contour.
*Addition of the high-mount spoiler relaxes the backlight-to-trailing edge exit angle to 7.3-degrees, with the implication for direct downforce.
* Deleting the high-mount spoiler, and extending the decklid 10-inches, intercepts the original, 'slower' template, which also matches the 1981 VW-Flow Body contour ( Cd 0.14 ) and 2019 GAC ENO. 146 contour ( Cd 0.146 )