What are the REAL downforce numbers for a stock 996 TT, and one with the factory Aero kit. Can’t seem to find it anywhere. Porsche’s marketing literature uses vague phrases like “ to lessen lift” or “increase down force” . Has Porsche published measured figures for these to iterations?

When I hear “lessens lift” , I read that at meaning that at high speeds your TT is experiencing positive lift.

You could find this info in the manuals or literature that came with the Ferraris 355 and 360 Spiders I once had. If memory served me right the 355 got 95 lbs of downforce at 120 or 150 mph. With more wind tunnel designing of the underneath, the 360 came in at 395 lbs downforce and very high speeds.

Has anyone seen published figures for the stock and aero Porsche TT’ only? Thanks.

 

It has to be an amount of vertical force @certain speed. The number changes linearly as speed increases.

Also the total force pushing the car to the ground is the resultant of downforce and lift which not change at the same rate...

 

Thx. I was after published figures showing the downforce ( or lift ? ) in pounds at a given speed, ie - 150 mph for a TT

[QUOTE=Gabriel]It has to be an amount of vertical force @certain speed.

 

LIFT!



Go Fast

There's indeed little information about lift and downforce numbers for these cars, let alone aerokits.

What the aerokit does is increase downforce to improve handling, but not neccesarily because the stock TT has negative lift.

To answer your questions, the 996TT has a coefficient of front lift of 0.02 and downforce of -0.01 in the rear. This means that the car is neutral at speeds of 125mph, close to zero lbs.

The 996GT3 with a protruding front lip and the aerofoil, has zero lift at 125mph in the front and close to 14 lbs of downforce. At 186mph, downforce in the rear becomes close to 30 lbs. I would think the 996TT aerokit to be similar.

The 996GT2 has seen a few changes vs the 996TT to reduce front lift via the opening on the top of the front bumper, air flows through the front bumper and is extracted by the opening on top, reducing effectively lift and also improving drag. Front downforce on the GT2 at 125mph is about 5 lbs and rear downforce about 17-18lbs, climbing to about double those numbers at 186mph.

Keeping drag in check while improving handling through incremental downforce is a real challenge, and Porsche for one are very concious of that, especially as new more powerful cars need a wider body and track to improve handling at high speeds and to serve homologation purposes in cup cars.

Hope it helps.

 

I just spent a full day at AeroDyn's Tunnel #2 with another model/brand of car, and although my Porsche TT wasn't in the tunnel, the operator constantly refered to the "Black Porsche w/GT2 wing in the parking lot" for reference to what "works".

Some things I learned... Near wake vs. Far wake... Getting the air to fall around and over the back of the car, and come from under the car meeting as far off the rear bumper as possible is what makes a car more stable, and faster. The GT2 wing extends further off the rear deck of the car than the Twin Turbo's. Some question if the GT2 nose would assist, but the tunnel operator, Bob Smith, who has tested a bunch of cars in his 30+ years said that the front on the GT2 doesn't produce significant amounts of down force. It is "better than the Twin Turbo, but not drastically better. The rear wing is where the money is best spent...

Best tip of the day... Air is measured coming thru the back out of the radiator of ANY CAR at.... 15 miles per hour... Amazing... Doesn't matter the speed driven, 80mph or 180mph... the speed of the air is so impacted flowing thru a radiator that it is slowed to just 15 miles per hour exiting the radiator...

http://www.aerodynwindtunnel.com/ for more info on the tunnel.

Mike

 

Why Ferrari has more downforce that Porsche in any model?
I think Ferrari is more like a racing car desing that Porsche....in a Ferrari like 430 or 360 the engine compartment is completely closed! and is a Porsche you can see the engine perfect!

I think Ferrari is better in CX and Downforce.....

 

Forgot to mention, in a few books on the 911 that I currently own, the CD #s are refenced for the 996TT as .308! As a point of reference, the C5 corvette (97-04 models) measured .287 CD.

I'll doublecheck when I get back to my office and see if they reference the downforce numbers.

Mike

 

Great posts, Jean & Mikelly!

As a benchmark, I was first hoping to see if there were ANY published numbers for downforce [ or lift] for a stock 996 TT.

Then, see if Porsche A.G. also gave any figures for a 996 TT with their factory Aero package. Or are they afraid to do so, lest Porsche have to admit that this $11,000 ( Cdn.), is merely cosmetic bling? ( This is the same company that will charge you $1,000 for foot-well lights. : (

Even if the numbers are neutral, that is useful info, as it means that any unweighting of the front wheels might only be from weight shift when accelerating.

Let’s face it the P-cars do hold their own in sc racing.

Regarding why the newer 4RE’s have good numbers, Paris. On the 355, there was a bit of undercarriage sheathing.

The 360 was developed in a wind tunnel.
They were able to design an inverted air foil and sheathed the entire underneath. It started at the front where there is a tunnel between the rads, and goes up again at the back. On the Enzo the downforce at top speed was so high they had to look for ways to decrease it ). At over 1,000 lbs, it would have affected the suspension. ( You can see these exaggerated rear diffusers on the GTI corvette & viper ).

But it would be nice to know the stock numbers for our P-cars. Thx for comments.

 

Well ferraris are wider, a bit lower, with less bulky cabins and more angled windshields...

I am sure porsche could do better in drag coefficient and downforce. I am not sure whether the product would look like a 911 anymore though.

 

Try C$1800. Ouch!

 

I'm filing that one away for when I have a few spare dollars for body mods. Thanks for posting!

Jeff

 

I asked Strosek about my front lip and rear spoiler when I bought them. This is what they said..

"Yes, the Strosek 996 Turbo has been wind-tunnel tested. We have a lot of data…but you will get through this rear wing about 40 kg more down-force at high speed as with the standard wing. The front spoiler will give you 18 kg more down-force at the front axle"

My guess is the factory aero kit is similar. Maybe more in front and less in back, but, again, that's an uneducated guess.

 

I thought Porsche advertised a lower drag coefficient for the 997TT, compared to a 996TT?