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- - spoiler (http://986forum.com/forums/performance-technical-chat/3700-spoiler.html)

Quote:

Originally Posted by MNBoxster

Hi,

If you want to keep the spoiler up all the time, raise it manually and then pull the Fuse! :)

So far as the Aftermarket Wings, these are very different from Spoilers. They really aren't 'Wings' at all, they're much more like Ailerons. A 'Wing' uses the motive force of the Car (Engine) to Push the Air out of it's way. Since Newton's 2nd Law of equal and opposite reaction is present, an equal amount of reverse force is exerted on the Wing pushing the rear end down, just like the Ailerons on an Aircraft.

A Spoiler operates under a completely different priciple. An actual Wing doesn't really create Lift, that is a misnomer. Air flowing faster on one side of a suface than another experiences a Pressure Drop (Bernoulli's Principle). A Wing works because the air on the upper (or curved) surface flows faster and so has a lower Pressure and actually Sucks the Wing upward. The airflow going over a Boxster moves faster at the rear of the Car than the air flowing underneath it, so it sucks the rear upward. By slowing this air down, or, Spoiling it, the negative pressure it exerts on the rear of the Car is reduced.

So a 'Wing' actually Adds a Force to the equation, while a Spoiler removes, or prevents it. Hope this helps...

Happy Motoring!...Jim'99

PS A Partial Vacuum creates quite a bit of Drag (robbing power and speed), by using the Spoiler to cleanup the Airflow on a Boxster, the Cd (Coefficient of Drag) is actually reduced by an additional 0.4 according to Porsche. A 'Wing' on the other hand would create quite a bit of additional Drag on the Car.

Great explanation on this! One question as the spoiler is actually disrupting air flow how is that lowering cd? I would think any object side mirror or solid spoiler would negatively affect airflow because of additional drag.

Quote:

Originally Posted by gRed04

Hi,

Well in aerodynamics, all things are pretty much a trade-off. You're quite correct that the spoiler would cause additional drag. But, a couple things:

The spoiler isn't necessarily in the airflow (I can't be certain of this not having any actual Wind Tunnel Data on it), but, it does sit pretty low on the rear. Although as you say, it very well may add some Drag.

But, the AirFlow (due to the Negative Pressure it generates) may add even more Drag, so the overall effect of the Spoiler is to reduce the total Drag on the system resulting in a net overall lower Cd.

Another Real-World example of this are the Wingtip Vortex Generators you now see on several Commercial Aircraft. They generate a vortex which is very Drag Inducing, but they help more than they hurt by containing the air on top of the Wing which wants to flow off the outside edge interupting Laminar Flow (which creates Huge Drag Penalties), resulting in lower overall Drag.

I studied Aerodynamics in School many years ago (BS, MS), but computer modeling was such, that these things were, at that time, undiscoverable. Since then, Computers have advanced the science tremendously.

Happy Motoring!...Jim'99

Check my spoiler

have got alot of good comments..peeps like alot...

i really would like to have a spoiler that goes in the stock position, moves up and down, but goes higher up at speed than the stock spoiler.

Quote:

Originally Posted by series 7

i really would like to have a spoiler that goes in the stock position, moves up and down, but goes higher up at speed than the stock spoiler.

Hi,

My first impression of your post is Why? Porsche spent a lot of wind tunnel time determining the proper shape and deployment height of the spoiler.

You might think more is more, but I suspect that if you raise it higher, you diminish it's effect. And, the back end of the Boxster will get very squirrely at speed without it. Aerodynamics is a very complex thing, you can't just arbitrarily do this or that, the results, more often than not, will be negative.

If it's the look you're after, you'd be trading off looks for function. In this case, not a good trade IMHO.

Happy Motoring!...Jim'99

Interesting discussion, but does anyone really think they are going to improve the years and expertise the Porsche designers have instilled in their product? Porsche is in the business of making fast cars...it is in their best interest to have fast cars. Take a look at the Coefficient...it is one of the lowest around when you don't factor in supercars.

Great discussion on aerodynamics. I wish the planes I flew were fast enough to worry about winglets and vortex generators.

Cheers