G Man

I really like the look of the "s" model rear wing or spoiler or what ever it is called. How much trouble is it to retrofit this to a non "S" car? Will I have any negative effects if I installed this without the front spoiler?

autochicago

No negative effects persay, except to your wallet. You can generally find one used for around $150, up to $300 for a pristine one or probably similar for new parts. But, that's the easy part, besides drilling the holes in the hatch to mount it, also easy. You also have to replace the rear 1/4 window seals and somebody correct me if I'm wrong, also the glass is a different part. See the vendor catalog. You will see. All in all, it's not a difficult proposition, but a pretty expensive one. You're better off going with a GTS style rear wing, if you like that style.

jaymz

do you meen the s4 type wing or the standerd s wrap around??

Lizard928

to install the S rear wrap around wing to a non S car you will need, S rear quarter panel window trim and seals and of course the wing, you can drill your existing hatch to accept it. and just below the rear quarter panel window for the bracket to mount the side pieces

928FIXER

Pano did an article on how to do this about 10 years ago.I do beleave it was penned by Kim Crumb

heinrich

I wish I could delete my rear apron and front frock ... I love the clean ob look.

BrianG

Ya, the grass is always greener on the other side. I'd like the S4 wing on mine!!

Jim bailey - 928 International

There is no drilling needed on the rear hatch the metal trim is removed and trim clips removed and the center section bolts through the existing holes. The 1/4 window rubber is different as is the trim AND two brackets need to be added for the side portions of the S spoiler. The aerodynamic effect of ANY stock front / rear spoilers is next to nothing. The body lift of a no spoiler 928 at 140 MPH is very few lbs. I firmly believe that the S spoilers and S-4 wing were influenced far more by the Marketing department than by Engineering.

SharkSkin

Nicole mentioned at one point that the S spoilers took the car from a .42 to a .36 drag coefficient IIRC... Would be interesting to know the source. I too doubt that there is any meaningful downforce to be gained from the mod.

autochicago

Good point by Jim about not having to drill holes. My comment about drilling holes was misleadingly guided by a fiberglass GTS replica that somebody put on my early hatch.

Still doesn't make it an easy job. You and heinrich should trade parts But you're still going to need new 1/4 window seals IMO.

I haven't ever tried to get them out intact ... anyone else had any luck?

G Man

Thanks for the input folks. I didn't know what was involved, but it doesn't sound too bad. I'd be game for a trade if Heinrich is game.

heinrich

Jim I'd be all over that offer were it not that I'd have to fill two holes in my rear fenders and of course up front on the fenders .... As to lowering drag, impossible. poilers and splitters make a car less slippery and more sucky. Suckage ~ Drag .... So, make the car suck better (more downforce) and you immediately increase drag. Lower drag and you don't necessarily lower drag, unfortunately. And by adding downforce aids, you often increase frontal area, increasing drag.

Add spoilers and splitters, add drag, add downforce

SharkSkin

Not necessarily, if they help guide air properly. Depends on the design. Designs intended to create downforce must increase drag, because the downforce has to come from somewhere. Designs intended to simply smooth out airflow can actually reduce drag. IIRC that was the intent behind the "S" stuff, but hey, maybe I don't recall correctly...

Nicole

G-Man: Contact Beth in Napa and pull whatever you need from the carcas she has sitting in her driveway! While doing so, you will see, if you want to go through the trouble on your newly repainted beast.

The factory has issued a service bulletin at some point that the rear spoiler should not be mountd without the front spoiler. REason being that at high speed this could cause instabilities.

To add to Sharkskin's post about downforce: These spoilers might not bring a lot of direct downforce, but that does not automatically mean they don't reduce lift because of the revised air flow. The 928 technical documentation book eplains it in a sense that the load on the weels no longer changes as much at high speed. It also states that the front spoiler improves air flow under the car and improves drag coefficient significantly.

I don't have any lift/downforce data, but the S spoilers (both) reduce drag coefficient from 0.42 to 0.385. That's about 10% reduction in drag. For comparison, the S4 is down to 0.34, the GTS up a little to 0.36. I have to find the source again - has been a while since I last looked it up.

Jim bailey - 928 International

from The book; Excellence Was Expected...."at it's maximum speed of 140+ mph the lift at either end was no more than 60 lbs ". So a 3,350 lb early 928 with a 150 lb driver will at 140 plus still have about 3,370 lbs pressing down on the tires. The 928 body shape was wind tunnel tested unlike the 911 which was eyeballed.