The rule of thumb for aero accessories is what...

"claramag, Mustaco Master" (claramag) 11/18/2014 at 10:24 • Filed to: None

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...unnecessary, unless you spend excessive time above 120 or so? We all know mom's Corolla with a 1' spoiler is stupid, but how fast would little Rick have to get it before he could justify it?

(No, I'm not asking so I can slap a wing on my Mustang. She tries breaking 95 and the windows start shaking like a polaroid. !!!error: Indecipherable SUB-paragraph formatting!!! is not a good sound next to my ear)

Party-vi > claramag, Mustaco Master 11/18/2014 at 10:29

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No canards? This model is BULLCRAP!!!

Aaron M - MasoFiST > claramag, Mustaco Master 11/18/2014 at 10:29

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You know what spoilers are quite useful for every day driving?

Wagon spoilers. Because a wagon has a big flat area in the back, a low pressure area forms very easily, causing more drag and reducing fuel economy. Putting a spoiler there breaks up the low pressure zone, and you'll see fuel economy improvements even at normal highway speeds.

Even more useful when the back of your car is completely flat and completely vertical.

Leon711 > claramag, Mustaco Master 11/18/2014 at 10:29

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common misconception there, aero always works but there is a finite limit to it's effectiveness. depends on rick's angle of incidence. bigger wings work better at low speeds in terms of lift to drag ratio.

Chteelers > claramag, Mustaco Master 11/18/2014 at 10:30

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Probably depends on how aggressive the wing is. Formula SAE cars with wings are designed to work at relatively low speeds. My guess is the vast majority of aftermarket wings are not actually designed with any actual aero performance.

nermal > Aaron M - MasoFiST 11/18/2014 at 10:37

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The back of my GTI is rounded and spoiler-ed, yet it is still looks like the equivalent of a road swiffer after driving any measurable distance. It has to be due to some type of aerodynamic wizardry.

It gets even worse when there's salt on the roads. At a certain point you just give up on keeping the back window clean, and use the side mirrors.

OPPOsaurus WRX > Aaron M - MasoFiST 11/18/2014 at 10:38

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i can do a wagon spoiler

nermal > claramag, Mustaco Master 11/18/2014 at 10:38

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Large spoilers are for race cars that need them. Road cars don't, therefore a large spoiler on your road car makes you a doosh.

roflcopter > claramag, Mustaco Master 11/18/2014 at 10:39

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Spoilers work at any speed, it's just a matter of effectiveness. Ever see an autocross car with a near vertical plexi wing on the back? They actually make a difference.

roflcopter > claramag, Mustaco Master 11/18/2014 at 10:40

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I actually really like this look. It kind of reminds me of a mix between the in-wing headlights on planes and old school LeMans stuff.

Aaron M - MasoFiST > nermal 11/18/2014 at 10:40

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A spoiler is so-called because it "spoils" laminar airflow. Arguably, the spoiler will make the road dirt problem worse by increasing turbulence (which is still better for drag than the low pressure bubble caused by laminar flow) and slapping more crap against the back of your car.

claramag, Mustaco Master > Aaron M - MasoFiST 11/18/2014 at 10:41

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I remember hearing about the poor drag on flat backs, is it a culprit in why tiny city cars don't do great on the highway?

Milky > claramag, Mustaco Master 11/18/2014 at 10:42

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Not necessarily true. There is a reason why all TTs have spoilers now and why I can't put mine down above 60mph.

BATC42 > Aaron M - MasoFiST 11/18/2014 at 10:42

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Weirdly I never thought of it that way. Do you know what kind of improvement one could see after slapping a spoiler ? My parents could use it on their Passat wagon.

claramag, Mustaco Master > nermal 11/18/2014 at 10:42

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but highway handling bro!

ly2v8-Brian > claramag, Mustaco Master 11/18/2014 at 10:45

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that model doesn't look like this.

Aaron M - MasoFiST > BATC42 11/18/2014 at 10:46

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I'm not going to try and claim it's a huge improvement, a couple mpg most likely. The benefit would go up at higher speeds...you're more likely to see that you lose less fuel economy when going fast on the highway (say 70+) than seeing that your combined fuel economy goes up (I'd still imagine this does almost nothing noticeable at typical surface road speeds).

nermal > Aaron M - MasoFiST 11/18/2014 at 10:47

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Huh. I learned something today. Thanks!

claramag, Mustaco Master > ly2v8-Brian 11/18/2014 at 10:49

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Crap.

I mean...don't you realize, we're talking about if aero parts are necessary so in a in depth troll I chose one that left out an aero part because was it...necessary...?

Yeah I just forgot about the canards

Aaron M - MasoFiST > nermal 11/18/2014 at 10:54

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This is more related to dirt than aerodynamics, and shows that as the dirt is coming up from the road, the spoiler likely isn't doing much:

ly2v8-Brian > claramag, Mustaco Master 11/18/2014 at 10:54

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Why's it matter to you? If people want to put stupid shit on THEIR cars why do you care?

claramag, Mustaco Master > ly2v8-Brian 11/18/2014 at 10:56

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Um, curiosity? A desire to have at least a cursory knowledge on the science behind the fashion? You know, shit like that

macanamera > claramag, Mustaco Master 11/18/2014 at 11:00

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Any additions are just completely unnecessary (performance-wise) on a road car. Furthermore, on track cars, it's not as easy as slapping a massive wing on and calling it a day. A large increase in downforce drastically changes the friction coefficient for that end of the car, especially at speed, and it can drastically change the way a car is balanced and the way it drives. Aero is way more complicated that most people think.

BATC42 > Aaron M - MasoFiST 11/18/2014 at 11:02

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Even a couple MPG could be satisfying with gas prices like the one we have over here in France. Especially since our highways speeds are up to 130 km/h (80 mph). I'll see if I can fin something nice.

Aaron M - MasoFiST > claramag, Mustaco Master 11/18/2014 at 11:13

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Yeah. In essence, the sharper the angle from your roof to the back of the car, the sharper the flow separation is between the essentially laminar flow over the roof and the turbulent flow around the back of the car. The spoiler breaks up laminar flow at that trailing edge in such a way that the flow separation is gentler, reducing the pressure differential, reducing aerodynamic wake, and therefore reducing the amount of air your car is pushing through and/or pulling along with it. This is somewhat oversimplified; I am a mechanical engineer but only took one semester of fluid mechanics.

claramag, Mustaco Master > Aaron M - MasoFiST 11/18/2014 at 11:22

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Hmm. Way more science behind it than I realize. I think I need to go read some wikipedia

STIKleinWagon > Aaron M - MasoFiST 11/18/2014 at 11:35

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http://www.motoiq.com/MagazineArticl…

mmmmm ANSYS....

STIKleinWagon > OPPOsaurus WRX 11/18/2014 at 11:36

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http://www.motoiq.com/MagazineArticl…

Aaron M - MasoFiST > STIKleinWagon 11/18/2014 at 11:43

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MotoIQ does good stuff. The WRX is not a particularly aerodynamic car, though that model illustrates somewhat the difference between a spoiler and a wing. Key quotes:

"Part of the reason for the top roof line spoilers on the STI is to reduce this [rear] wake, particularly on the hatchback model."

"The large wing in the rear adds to the total downforce generated but downforce does not come without costs."

Wings typically increase drag on the car but do it in such a way that increases downforce. Spoilers reduce wake (and therefore drag) by reducing flow separation at the back of the car.

This is also why the 07 WRX was the last one to have a protruding hood scoop: great for air scavenging, awful for aerodynamics. The flush-mount ones in newer cars work good enough on the road, but have caused intercooling problems for anyone trying to use a newer WRX in rally.

OPPOsaurus WRX > STIKleinWagon 11/18/2014 at 11:48

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i've heard you can get like 30 mpg with just an engine program. I guess they run super rich. I wish he used a standard hatch wing instead of the racing model. That was a good read tho. He is right and wrong about buying it for the fuel economy. I actually did as it was an improvement over my Sport Trac which probably got 15 MPG at best so 23/24 is awesome for me but yea, there are many better options but how may of those can give you whiplash with just the go pedal. (i also only have the WRX but a lot fo that still applies) I was really amazed at how crappy the MPG was for such a small car.

STIKleinWagon > OPPOsaurus WRX 11/18/2014 at 11:54

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I put the COBB 93 tune on mine and it gained like 1-2 MPG. They have a fuel saving map (which basically turns down the boost) that can gain you quite a bit of MPG, but where is the fun in that?

STIKleinWagon > Aaron M - MasoFiST 11/18/2014 at 11:55

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Yeah you get flow separation (and no flow to the intercooler) at higher airflows.

OPPOsaurus WRX > STIKleinWagon 11/18/2014 at 12:04

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maybe it was another tune, again this is coming from a friend who was talking about a co-worker so I can;t say how reliable the facts are. He was supposedly getting 28-30 mpg with a bump in HP. He said Subaru programmed the fuel mixture to be unnecessarily rich

Aaron M - MasoFiST > OPPOsaurus WRX 11/18/2014 at 12:14

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I get 28-30 mpg highway with mine. I used to do 25 mpg combined but the new clutch (and lighter flywheel, specifically) killed my city mileage. Where I used to get 20-22 I now get 17-19.

Aaron M - MasoFiST > STIKleinWagon 11/18/2014 at 12:15

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I gained about the same amount when I went Stage 2. My fuel economy stayed consistent as I kept upping the power, until I had to do the clutch/flywheel.

OPPOsaurus WRX > Aaron M - MasoFiST 11/18/2014 at 12:28

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28-30 stock? i've gotten 26 but that was drving like an old lady

Gizmo - The Only Good Gremlin, but don't feed me after Midnight > claramag, Mustaco Master 11/18/2014 at 12:33

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You may also want to look for Land Speed Racing sources. LSR designers have some great reading for you about spoilers, wings, diffuser, etc. The LSR forum has a section dedicated to educating the amateur.

Aaron M - MasoFiST > OPPOsaurus WRX 11/18/2014 at 12:35

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Is yours stock? The stock tune is pretty rich off-boost, so a tune improves your fuel economy. I get 28 on a typical road trip, I can get 30 if I keep the speed below 75.

Also, the 06/07 has a 3.7:1 final drive, all the other WRXs have a 3.9:1 final drive...that makes the 06/07 the hypermiler of the group (comparatively, of course).

OPPOsaurus WRX > Aaron M - MasoFiST 11/18/2014 at 12:39

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i have a '14 WRX hatch, 100% stock

Aaron M - MasoFiST > OPPOsaurus WRX 11/18/2014 at 12:44

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I bet you can start seeing 27, 28, maybe 29 on the highway with a tune, but I think cresting 30 may be limited to those of us with the lower final drive.

claramag, Mustaco Master > Gizmo - The Only Good Gremlin, but don't feed me after Midnight 11/20/2014 at 09:06

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Oh wow that site is full of all sorts of resources.

Aaaaand bookmarked

Gizmo - The Only Good Gremlin, but don't feed me after Midnight > claramag, Mustaco Master 11/20/2014 at 11:17

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Good for you. My friends and I set a couple new street car LSR records at the Texas Mile last month. Even the newbies understood, it takes 1100HP+ to drive a CTS-V 200MPH+ in a standing mile and almost half that power is overcoming wind resistance.

Ac a side note, one thing we verified was the OEM design of the brake ducts and undercarraige tray makes the tray and the front inner fender skirts blow out at ~187MPH - we had to zip tie all the parts together cause the push pins failed.

claramag, Mustaco Master > Gizmo - The Only Good Gremlin, but don't feed me after Midnight 11/20/2014 at 12:24

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And I'm just over here zip tying bumpers on because of their incompatibility with parking lot lights

Still, I'm digging the science behind high speed aerodynamics; it's like inverse flight. What with it's extended high speed run times maybe I ought check out NASCAR...