LAT

Geoffrey;
Can you provide more info on these wind tunnels, I am willing to experiment. Either here or PM me.
Thanks

chris walrod

That is awesome!

Our tunnel is pricey at ~$3500/hr, 10 hr per day minimum -- 50% scale.

TB993tt

The extent of my enquiries for the 993tt was to quiz RS about their 210mph + 993s and especially that 221mph red one which just has stock rear spoiler and Strosek front PU - the answer was they all wander at very high speed unless you adorn them with Motorsport aero and then you will struggle going very fast....
I comunicated with Marc Bongers, Ruf's expert who stated that the Ruf CTR front PU does NOT give any additional downforce (I was impressed with his honesty)
I asked him about the Cd and CdA numbers he quoted in his book for the Turbo S (which were identical to stock body) and he said that Porsche had designed the S bdy to give additional downforce with the same drag - but no numbers anywhere.

I remember at the 993tt launch Porsche quoting that the 993tt has zero lift at 150mph - could that be true, can 27kg lift (measured by SA supertest) reverse into zero lift as the speed increases

I am pretty cynical about after market add ons, that spoiler which bb993tt pictured is made by Gemballa - looks functional but all the SA tests when they have put tuners Porsches into the windtunnel at 200kph have given worse results than the stock cars despite effective looking wings....

The new 997GT2 has 9kg downforce at the front and 29kg rear at 200kph, Techarts "windtunnel developed" bewinged GT Street has 8kg lift at the front and 6kg downforce at the rear at 200kph !! I aim to ask them some straight questions about this at the upcoming Essen Motorshow.....

Back to the 993tt, I have a new front PU/spoiler coming which has been "developed in a virtual windtunnel" and tested on the autobahn at 300kph - so we shall see what that is like

Jean

Here is a timely picture that was posted here before.. Interesting reading next to it. The rear deckild does get in fact massive airflow.. Check out the turbulence hot spots..

WHB Porsche

The above picture was from an article in which someone taped a bunch of short strings to the car in various places. The car was photographed extensively at mid speeds and the location of the strings shows airflow. Not the detached flow at the mirrors, windshield edges (exacerbated, no doubt, by the rain gutters), and the third brake light.

Jean

Yes it is on Autospeed.com

Geoffrey

Interesting. When I built my racecar, I paid close attention to flush mount everything I could, use the integrated GT2 Evo mirrors in the doors, and fabricate a undreside tray to keep the bottom as flat as possible. I'm also running stock rear wing compared to the bananna wing of most of the race cars. I haven't noticed any disadvantage against similar car, even in higher speed corners (110mph), and I can match speed with a 996 Cup car.

I don't know how much the small amount of airflow optimization I did helps the car, but it was fun nontheless. Perhaps I'll get it into a wind tunnel at some point.

graeme36s

I have to agree with Jean. The issue is not the back end but the front. Ignoring my 993GT2 as I have not had a chance to really wind her up my 9643.6turbo has seen the best part of 190mph although speedo/digital speedo only so probably sub 180ish. The front is the issue. The car had H&R 30mm lower springs and was dropped as far as it could go with the typical lower front stance. UK ride heights.

We were making these numbers a fair few times, 165mph before changing into 5th. Fairly quick to 175 but then the aerodynamics hit and took a while to wind up. You could really hear the wind noise change. At these speeds you knew that you did not want to be making any sudden directional changes and it was definately down to front end lift. I guess and hope that the GT2 arrangement will be much, much better. For increased stablity you definately need to be looking at the front end.

Ruf-Racer

First picture shows the add-on A pillar fairings are doing a good job! It's really cool to observe the air flow signatures,isn't it?

Cheers

R

TB993tt

I guess the "master" of 200mph + in a 993tt has seen this many times

The Ruf pillar fairings appear to do an amazing job. IF the flow lines accross the roof in the diagram below are correct (a big IF IMO since they are done at low speed) then the air flow in a straight linear fashion across the roof as one may expect.


With the Ruf inserts a fair lump od air appears to fire off the top of the Ruf fairing and shoot towards the middle of the rear window at that 75deg angle, with each side being a perfect mirror of the other - Could this be the rounded shape of the roof also causing this ?

MOD500

Great thread TB

Look forward to your thoughts on the new front PU.

At the recent v-max, a cross wind made piloting the banana absolutely terrifying, the way the car was wandering around at 180 plus was mind boggling and felt just too uncomfortable / unsafe. Think the sunroof coming out at 182 was maybe in some ways a good thing, as it prevented any further runs!!

Basal Skull

Is there some point where decreasing cd - sloped windscreen, loss of gutters - increase lift? I guess it is a compromise? Air flows over a longer distance over the car vs below like a air plane wing. By making the cars slipperier does it increase lift? May be the current windscreen/gutters help down force?
I'm surprised Jean and Geoffrey experience compressing down of the rear windows - would have thought it would be sucked out (like the sun roof that was lost - or did it cave in to the cabin) - longer distance traveled over the car vs below like a wing creating vacuum/lift above? Or is this just a case of me knowing a little about something but not enough to really understand phenomenon that I always get into...

Ag02M5

I was going to sell my RUF a-pillar aero pieces. I think I will go ahead and install them after seeing this. Great thread!

Jussi

I have also those RUF A pillar fairings and I think that they helped at high speed. They also reduce wind noise. Good value for money.

How about Turbo S model side air holes at rear arch? Do they lower air resistance?
I'm going to install them to improve air flow and cooling.

Felix

I've just checked my car as I still haven't washed it after a 2000 mile road trip on the continent and a run or three at Vmax. (Hey, it's meant to be driven, isn't it?).

On the driver's side (LHD car) the trace starting at the top of the A pillar comes off the trailing edge of the roof 28 cm from the rain gutter. On the right side the same meaurement gives 24cm. I can only assume this difference is from the wipers? No windscreen pillar inserts - yet.