Rich Sandor

$50 says they will be pointing down the hatch.

Mighty Shilling

I'll also place $50.00 towards that...

Porsche I know spent way too much time in the wind tunnel with these cars.

luckett

Yeah, around the inside of the intake tube in front of a Tornado (www.tornadoair.com) and an electric supercharger. That should be good for at least a 50% increase in HP/torque...

Mighty Shilling

Chris, I thought it'd be at LEAST 95% increase...

Fishey

I heard from this one kid with a honda with a similar setup that his car actually makes a blackhole do to the fact that not even light can escape the intake flow! Now his 1/4mile is .00000000000001 with a trap of ∞!

IMB951

He must have gone with this setup:

Crackmonkey

My friend and I had been toying with the idea for awhile I wanted to see what every one thought about it he has installed them on air planes before. I will deffinatly Perform the string test before I do anything. But if it causes lift ah just forget it.

BeerBurner

I prefer this method for cooling my beer.

BB.

88BlueTSiQuest

That only works if drag racing on water, where they allow a running start at the light tree. If you remember, in order for the generator on the DeLoreon to work properly, it had to achieve 88mph. And we all know that a DeLoreon won't hit 88mph during a ¼ mile run

Owain

Another application for vortex gernators in automotive aerodynamics is to help manage the flow of air under the body of the car. Generally, if you can limit the amount of air flowing under the car you can create a low-pressure zone and therefore a little suction (downforce)(technically speaking you're really trying to counteract a car's natural tendency towards net lift). This can be done by having an air-dam and splitter at the front, "splitting" off some of the air that was going to go under the car, and sending it elsewhere.

Then, though, you have a problem with the low pressure sucking in higher pressure air from beside the car. In F1 they found they could run vortex generators just behind the front wings, having the vortex run down the length of the car between the ground and the outside edges of the undertray. This would effectively create a barrier to separate the air under the car from the rest of the environment, maintaining the low pressure. Not as effective as the plastic 'skirts' they used to use as a seal but still a good compromise after the skirts were outlawed.

I'm not sure how effective these would be on a 944, though. The vortex would have to deal with the spinning wheels and might not survive past the front ones. Only one way to find out...TO THE WIND TUNNEL!

Also, the idea of using vortex generators to maintain laminar flow over the back hatch wouldn't be to maintain the natural lift but to increase the effectiveness of the rear spoiler to counteract that lift. It's counting on good airflow to do it's job. Just by eye, I would agree that the 944 probably does well maintaining the flow over the hatch, but only testing would tell. I once had an old Datsun 200sx that, over about 50 or 60 km/h in the rain the back hatch glass would remain completely dry. Great flow over the back of that car. There are lots of production cars with rear spoilers and wings that are probably completely useless, or minimally effective because they can't maintain the flow over the surface of the car. Production car designers are usually more concerned with airflow's accoustic properties than it's downforce/drag properties.

luckett

Don't some of the new BMWs have vortex generators on the mirrors?

Owain

On the wing mirrors? Interesting. Do you know what they're for?

Lousailor

Well here's my cut, and some of this has been said already. Vortex generators come in different versions. The most basic is a row miniature pieces of aluminum angle, mounted diagonal to the oncoming airflow. Another that was used on one of the planes I've flown was a triangular wedge, the base flush at the front and rising to a point at the rear (approx 18" thick). The goal of both of these is to stave off boundary flow seperation at lower airspeeds and higher angles of attack. Laminar air flow (air flow that is parallel to aerodynamic surface) builds up a lot of sheer force (re drag) and at lower speeds and/or high angles, this drag force interupts the air's momentum and causes turbulence and separation, usually resulting in random swirls and a lot more drag. Take your hand palm forward through a pool of water and you'll feel the increased resisitance as well as see the swirls behind it. Hold your edge forward, and you'll note much less resisitance and see much less swirling water. By creating small vortices in the boundary layer, you infuse the airflow with energy, overcoming some of the laminar drag effects, and allowing the entire boundary layer to stay attached to the aerodynamic shape longer. Since this technic is used primarily to increase wing lift at low speeds, and high AOA it really doesn't apply to cars, whick are trying to decrease drag as well as lift. But if you wanted to use a fairly drastic spoiler to create downforce, vice just killing lift, they may have some benefit.

sharky47

I am the "friend" in question here. I used to be an aircraft mech. and installed several VG kits on different aircraft. They work on aircraft by "attaching" the airflow longer, and at higher angles of attack to the control surfaces. This lets you maintain control of the aircraft in near stall and stall situations.

I was thinking about using them on the 944 to attach the airflow to the hatch longer to make more use of whatever wing you have back there. Yes, they would increase lift slightly, but if the end result is to make the wing more effective, then that would surely outweigh the amount of lift generated. The key is keeping the air in the hatch area non-turbulent, the wing or spoiler can work much more effectively using "clean" air rather than turbulent air.

This is all based on *if* the 944 needs it, I was planning on attaching several hundred pieces of string to the hatch and observing the airflow patterns at various speeds. If they stay strait back most of the time, then there is no need for VG's. If they are pointing backwards or waving about, then it might be worth further investigation.

Daddio

1. Laminar flow is low drag, not high drag. Good primers on this topic are Alex Strojnik's "Laminar Aircraft Design" and Bruce Carmichael's "Laminar Lightplanes."

2. Vortex generators act to keep the flow over a wing turbulent, but attached. In some light aircraft, properly designed and placed VGs increase wing efficiency such that much lower landing and stall speeds are available, meaning shorter takeoff/landing roll and therefore better safety.

3. Vortex generators on the top of our cars may well result in enhanced lift from flow over the car body, WHICH IS JUST EXACTLY THE OPPOSITE OF WHAT WE WANT.

4. If you want better handling and traction at speed, look to front spoiler or splitter solutions, to keep air from being trapped beneath (and so lifting) the nose. If you go the wing route, remember that the wing must be elevated into reasonably clean airflow, unlike the rinky-dink wings used on ricers, which are purely cosmetic. Remember also that the wing airfloil is INVERTED, so that it pushes down on the car, holding it snug to the road. Such downforce should be applied at a point in front of the rear axle, lest the axle act as a fulcrum and lift the nose somewhat.