JEBDOG hope you dont design airplanes!!!!...lol if what you say is right about original design then its true the wing dos afect the air flow(positive or negativly) IT IS A LARGE AIR FOIL!!... ever noticed the dust trail behind a 928? or how the road grim builds in the back...airflow travels all the way down the back....but thanks for your guess. > tommytomaso

 

From Porsche Excellence was Expected..... " Wind tunnel tests showed the chosen contours ....at maximum speed lift at either end was no more than sixty pounds..." That was the original no spoiler design . Lift never was never an issue for the 928. Unfortunately wings spoilers ducts scoops flaired fenders have all been generally accepted as looking like a race car. The reality is a properly designed body shape needs none of those. The 911 turbo had to have all the additions because the basic 911 design was never wind tunnel tested simply drawn by eye and originally ran rims about 5 inches wide ! Porsche refers to the S-4 rear "wing" as simply a spoiler which like the S rear lip spoiler probably has more to do with creating some turbulence to get the air to tumble down and help fill the void created by the car passing through the air to reduce drag. Much about aerodynamics is NOT intuitive.

 

the 928's shape is very smooth and many spoilers are just for looks... and the original 911's whale tail is more for cooling? air feeding? than handling. but the Audi TT is a very good example of how little an airfoil has to be to be affective. im thinking that eather the "betterbodies" S4 wing is a improper copy or that its just not a good design for the OB short tail. if you took a section view of the wing it is a near perfect airfoil(airplane wing shape) ....but i have just thought of a way to test it..
ill not compleatly close the hatch and make sure thiers no air flow inside the cabin and see what happens. if it lifts the hatch(till air rushes in) so it should go up and down(bobing) unless its doing its job..or no job at all(it should stay down) ill tie it down just incase.
Now was the original S4 wing adjustable? club sport? or are people confusing the fold up design for adjustable?...and if it was adjustable dos it make that much of a dif?

 

The S-4 rear spoiler was not adjustable the flip up early 87 was to make it easy to clean the window. The 911 body had about 320 lbs of rear lift at 152 mph this was in a car weighing about 2000 lbs as raced in 1970-71. The addition of the Burzel or "ducktail" spoiler on the 1972 Carrera RS reduced the lift to 93 lbs and dropped the drag coefficient from .41 to .40 . The later turbo picnic table rear spoilers featured extended upcurved sidewings for more down force then evolved to bulkier flatter designs to house the air to air intercoolers. Like I said the 911 shape had a BIG problem one 911 racing variant even had a second rear window rear hatch section mounted more horizontally above the factory parts!

 

I am in the process of a complete repaint( original "slate blue") on my 84S, I am assisting the body shop in tear down, prep and assembly, and we removed the rear spoiler and air dam today. Im my opinion, the work required to install these items would not be worth the time and expense. The rear three piece wing requires two tabs per quarter panel to be welded on after you remove the windows and replace the mouldings and the hatch would require drilling for the screw and four stud install. Before you spend the money and hours you might want to consider the mindset of having a "rare" 928"...

 

I am hearing alot of this... but, my car is headed in for a full body repaint also... done by a 928 guy. well, after it is sorted out if it will ever run again (praying). anycase. would you or anyone say if it worth it that I am getting the rear hatch with the spoiler already installed, and the side spoilers, plus the correct windo trim, for $250? I mean, at that price, the hatch alone is a deal, no?

 

If you are getting a hatch with the spoiler,(all three pieces) for $250 and your are planning to do a paint job by a 928 guy, I would consider doing the "upgrade" if you have to have it. Also, don't forget about the window molding differences and welding the front two tabs, bolting the rear two tabs. I think I still like the spoiler-less/naked look just because everybody wants to have them...

 

actually, it is better than that even... I already have a hatch with the S4 wing, I will have a hatch with the S spoiler, and I have a hatch from the 79 that is naked... perhaps I should weigh all options before commiting to one.