dzander

I will be removing the rear wing on my GT4, and am wondering if anyone has come across blanking plates to seal the slots through the top of the trunk for the vertical supports . I've called a few vendors, and nobody has heard of any available yet. To the guys that have removed your wing, what did you do to seal the slots? Does anyone have experience with 3D printing? It seems like it would be straightforward to commission some blanking plates from a parts maker. If there aren't any available, do any other wingless drivers want to get together to have some made?


Thanks in advance!

Petevb

What are you doing up front to balance out the aero? I prefer the wingless look as well, but if you don't reduce front downforce in proportion you run real risk as you approach triple digits.

stout

Aesthetically, I think I'd prefer it, as well.

I don't hate the GT4 wing because it's a functional piece and I like the way it breaks up the 981's too-smooth-for-me hatch, but 000 magazine commissioned Steve Anderson to do some illustrations of a 981 Cayman 2.7 with Spyder (GT4) front and rear bumpers with the Spyder spoilers, Spyder wheels, no GT4 side scoops, and a 904-like hatch—and it looked tremendous. I suspect a GT4 would be a lot of "fun" on that wheel/tire package, though it would lose a fair bit of rear-end grip. PeteVB can attest to that. On a 2.7, it would have been plenty of grip—maybe too much!

Based on the 981 Spyder, I suspect this setup might still be aero-balanced "enough," though that's just a guess. I suspect a quick and dirty path would be a Spyder front lip plus blanking plates for the rear wing. I'd rather add the Spyder rear spoiler, but that might take some work and $,$$$.

dzander

I don't plan to make any changes to the front to balance out the aero. As my car is a daily driver, I am rarely approaching triple digit speeds. The downforce provided by the wing (or even any reduction of lift) at sane speeds is minimal, and likely well within tolerances allowed given anticipated differences in fuel levels at the front and loads in the rear trunk. For the occasional track day, I will reinstall the wing...

Petevb

Let me still suggest that you consider swapping out the front splitter from the Boxster Spyder when you pull the rear wing. I'll explain why:

You're correct that at sane speeds aero forces are relatively small, and in a straight line they do work very much like different fuel loads in the car. Not many crashes occur in a straight line, however, and when cornering the dynamics are very different.

The Supertest wind tunnel shows the iron rotor GT4 has 38 lbs of front downforce at 124 mph, 68 lbs rear. Remove the rear downforce and the front will increase to around 50 lbs- think seesaw.

We don't have aero data for a Cayman without a wing, but we can bracket it. A Boxster Spyder makes 15 lbs of lift @124 with a deployable spoiler, a stepped rear deck and no front downforce, so we know it's well more than that. Meanwhile an old no spoiler 911 made nearly 200 lbs of lift at the same speed. The spoilerless Audi TT was 150 lbs; I'd guess at a bit less than either of these.

If we split the difference and go with 90 lbs due to shape, then add a bit to both the front and rear due to the seesaw effect again (load added to nose of the car will lift the rear up) to come to a guess of 60 lbs front downforce, 100 lbs of rear lift.

As you rightly point out you could easily come to similar relative values by running a bunch of heavy luggage up front with a full tank, so it doesn't sound so bad until you consider the dynamics.

The great thing about downforce is that it's extra force pressing the tires into the road without the normal penalty. The 60 lbs of downforce is going to increase front axle grip by 4%, but without an extra 4% of mass the front wheels need to push sideways when cornering (as if you just added luggage). Basically the front will get 4% more stuck, while the rear will get 6% less stuck.

A 10% difference might not sound like a lot, but think in terms of fitting 10% less sticky tires, MPSC2s up front and old all seasons in the rear, and you start to get the picture. Obstical avoidance on the freeway is probably worst case- you swerve violently to avoid something on the road, the front sticks like glue and the rear steps out.

The original Audi TT was recalled worldwide when an aero imbalance of a smaller magnitude killed a number of drivers back in 2000. The crashes occurred mainly in Germany, as below 100 mph even bad aero isn't all that bad. Thus if you're diligent and serious about keeping your foot out of it you should be ok, but you should be aware of what will happen if you ever get more enthusiastic. This effect will grow exponentially, and by 150 it will get positively lethal. The Spyder spoiler lip would be cheap insurance if you're in doubt- the numbers suggest it will nearly balance the aero out, and I'd happily drive the car that way.

Back to your original question, most common 3D printed parts will be very UV and heat sensitive and unlikely to last long even when painted. They will also need some surface finishing. There are some more durable 3D printed materials that are far less common, or some low volume resin castings made from 3D printed parts and silicon molds that might be more suitable if you can get a small group together. For one off I'd probably simply bite the bullet and machine from aluminum.

Beantown Kman

Subscribed. I'd be happy to remove the wing if there was a good solution to cover the slots. I'd also consider the spider front lip. The rear wing is a bit much when I'm tooling around town.

dzander

Pete - Thank you for such a complete and well thought out analysis of the aero effects. Certainly a lot to consider. I will look into a Spyder front lip, and always keep the possible imbalance in the back of my mind when burying the throttle! (Is that your long hood in the picture?! How can I learn more about that? It's amazing!)
I spoke to a engineer friend of mine today, and we came up with some ideas for creating a blanking plate. I'll update this post if/when we come up with something.
If you come across this post and know of someone already making them, please let me know. If you are interested in blanking plates for your own car, let me know and I'll start a list. More than likely, the more we make, the less they'll cost.
Thank you!

4carl

Years ago I experimented with taking the wing off of my Exige S. It supposedly provided 100 lbs of down force. Never liked the look so I took it off at a track day at BW . The first few laps it felt different almost lighter. Then approaching Magic mountian on 13CW @95 the back end just lifted huge OFF totally blinded buy shovels full of dirt being thrown in my face waiting for impact. Did 3 loops and stopped two feet from the guard rail. Learned my lesson on downforce and aero balence. Frankly up until then I thought a lot of it was bullsh-t. Carl

Petevb

Thanks, happy to share.

Yes the long hood is mine. If you click on the first car in my sig below it will link to a mini build thread...

bhk1004

I must be the only one that likes the wing...

RNGRJAG

Nope, I like it too. Please correct me if I am wrong, but I think all Porsche GT cars come with a spoiler. (911R not branded as such). Take the same wing and add it to a car that did not come with it OEM and I would hate it, though.

stout

To be clear, I like the wing, too—it is functional and, like (most of) the other wings on GT cars, really well handled. But I like wingless cars, too. Less advertising, and cleaner lines. Even so, I wouldn't mess with my GT4 to remove the wing.

However, if a (balanced) wingless setup had been offered by Porsche, I might well have opted for it.

switchface

I've always loved the ducktail type of look. Here is a carbon fiber ducktail like wing I had made for my previous 987.1 CS




I've seen a few awesome pics of RS's with the wing removed and it looks pretty mean.

tstafford

I liked it and like the one on my RS. Mostly I like that it helps keep the car on the road surface at the track.

jphughan

It's strange, when I first saw pictures of the GT4 I thought the wing might be a bit "much" on a DD, but somehow in person it works well, maybe because the car in general is low enough that it's not in your face? But now when I see a non-GT4 981 model it looks incomplete to me. Somehow the smoothness of the rear styling inevitably makes me think of a frog poised to jump whenever I look at it from behind.