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Login to post Forums » Grassroots Motorsports » Downforce, is it real?

Sept. 19, 2010 8:19 p.m. BigD New Reader

Ok I can believe that a car whose entire body is designed to effectively be an upside down wing, and travels at truly high speeds, like an LMP or Formula1 car. But do wings really make any significant difference in sedan racing, such as, say the Conti challenge cars?

I was watching a rerun of the last race yesterday and one of the Mazda3 wagons was tagged from behind which made its hatch pop open. I watched as it lapped the track with the hatch in the fully open position, never coming down, even in the straights and fast turns. Dorsey made a crack about the car being in "high downforce setting" but after a chuckle, I though, well where is the downforce? If a whole HATCH can't produce enough pressure to overcome the shocks/springs which are merely designed to keep it open... (I obviously didn't expect the hatch to close but become more or less horizontal on the fast bits) then do those wings actually do anything except slow the cars down?

Has anyone tried to put a pressure sensor of some kind, to see what difference the wings we run on our sedan derived track cars actually make?

Thanks! D
Sept. 19, 2010 8:31 p.m. Knurled HalfDork

It's been done for Fox Mustangs.

I can believe the hatch thing, if the windows were open. On further thought, they're probably not running super high downforce on that front-driver, just enough to add high speed stability.
Sept. 19, 2010 8:35 p.m. BigD New Reader

Cool, thanks! Do you remember what kind of pressure the wings generated? Like a rough speed vs force?
Sept. 19, 2010 8:55 p.m. Jensenman SuperDork

Dunno how much downforce an open hatch would make, but I'm going to hazard a guess that the hatch created a lot of drag but little or no downforce. Car sized wings do next to nothing at lower speeds (like highway speeds), they need a lot of speed to do anything at all. Also, if the ends of a wing or etc have no 'end fence' the air spills off the sides, meaning no downforce. For a perfect example, look at the size of the wings on a 200 MPH F1 car and notice the size of the end fences.

Or look at a 300 MPH Top Fuel dragster, notice how big the wings are and again how big the end fences are.
Sept. 19, 2010 8:59 p.m. Giant Purple Snorklewacker SuperDork
Sept. 19, 2010 9:17 p.m. JoeyM Dork

Jensenman wrote: Car sized wings do next to nothing at lower speeds (like highway speeds), they need a lot of speed to do anything at all.

Indeed. That's why A-mod autocross cars typically look like this: It takes a LOT of wing to generate meaningful downforce at autocross speeds.
Sept. 19, 2010 9:27 p.m. BigD New Reader

Good points, thanks guys!
Sept. 19, 2010 9:35 p.m. Jensenman SuperDork

JoeyM wrote:

Jensenman wrote: Car sized wings do next to nothing at lower speeds (like highway speeds), they need a lot of speed to do anything at all.

Indeed. That's why A-mod autocross cars typically look like this: It takes a LOT of wing to generate meaningful downforce at autocross speeds.

Yeah, that's George Bowland's BBR Shark. You should see those wings from the front!
Sept. 20, 2010 5:19 a.m. 11110000 Reader

I saw that hatch move too.

Besides the hatch being a completely wrong shape, and not sufficiently elevated above the air coming off the roof of the car, I think the pressure of all the turbulent air coming up from underneath the car, and around from the sides, was just about equal to the pressure on top of the hatch. If you heard the comment made when he came into the pits, you'd understand where the air is moving around in that situation - in a lot of cars with a near-vertical hatch or wagon door in back, if you drive with the hatch open, exhaust fumes push into the cabin and can make you feel really sick in a hurry.
Sept. 20, 2010 6:53 a.m. Raze Dork

These guys have a wing from a Cesna on top their Lemons racer, I've personally seen it in action. It's capable of generating so much downforce it can literally compress the suspension to the bumpstops at speed:

for more info www.perpetualdownforce.com/
Sept. 20, 2010 1:44 p.m. tuna55 Dork

Raze wrote:

These guys have a wing from a Cesna on top their Lemons racer, I've personally seen it in action. It's capable of generating so much downforce it can literally compress the suspension to the bumpstops at speed:

for more info www.perpetualdownforce.com/

Quick thumbs up to what may be the second best Lemons team ever, next to the Tunachuckers, of course.
Sept. 20, 2010 2:17 p.m. Grtechguy SuperDork

IIRC, the MKIV Supra wing generates 70lbs of downforce at 60mph
Sept. 20, 2010 3:10 p.m. 93celicaGT2 SuperDork

In before someone says that FWD cars never need wings.
Sept. 20, 2010 3:12 p.m. Grtechguy SuperDork

I believe the taller rear end on the vette acts as a spoiler. There's been studies done by BMW proving a taller rear end makes the car more efficient and controlled
Sept. 20, 2010 3:15 p.m. Stealthtercel Reader

I read somewhere that that dorky wing on the back of a Cobalt SS actually helps... if you're drafting John Heinricy around the Nurburgring. And if you're not, well, at least you look like you could.

Personally, I would take the wing off for a low-profile look. Not being noticed counts for a lot. Besides, Cobalt coupes with no wings or spoilers at all are surprisingly good-looking cars.
Sept. 20, 2010 4:08 p.m. wbjones Dork

93celicaGT2 wrote:

In before someone says that FWD cars never need wings.

I tend to agree with you.. except for all the Civic and CRX drivers in yrs past (don't know 'bout this yr) at the SCCA Nationals that have had the max amt of wing on their cars... ST/STS/SM etc... I figure that they've put a lot more time and money into their experiments than I'm willing to
Sept. 20, 2010 4:50 p.m. blaze86vic Reader

Yes they do. The biggest issue is that people don't take into account their vehicle speeds. But unless you have massive wings, they won't do much till you are going faster than 50mph (which is very little at auto-x events). At speed wings and such do generate a lot of downforce.

In the case of the open hatch, it's not the hatch it self that generates the downforce. It's the area of high pressure in front of the hatch that acts on the roof of the car that is causing the generated downforce. It's acting like a large spoiler.

There are three general methods to generating downforce on a car.

1: Is to cause an area of high pressure on the vehicle. On the rear this is typically called a spoiler, as it is attached to the trunk or rear most part of the roof, and is protruding into the air flow as to spoil the smooth flow of the air....hence being a spoiler.

2: Is to cause an area of low pressure under the car, with things such as diffusers, and snow mobile suction blowers.

3: Is to add a new separate component that has localized differences in pressure that yield downforce. Wings are a good example of this is, as they make downforce because of the difference in the pressures above and below the air foil. Splitters are also a separate system. As they mainly work by creating high pressure on top of the splitter, and low pressure on the bottom.
Sept. 23, 2010 4:38 a.m. bill New Reader

A protest is in order - the lift springs were obviously non-OEM, and the tap was intentional.
Sept. 23, 2010 6:15 a.m. Luke SuperDork

No. Downforce is actually a conspiracy perpetrated by tuning companies to sell huge rear wings to kids in old Hondas.
Sept. 23, 2010 7:18 a.m. Mikey52_1 Reader

Luke wrote:

No. Downforce is actually a conspiracy perpetrated by tuning companies to sell huge rear wings to kids in old Hondas.

And here's the crux of the issue...Hondaboyz will put anything on their cars that the latest forum tells them to. Blessed little original thought involved, and no research.

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