John 996 TT Cab

OK, color me confused. If you have the Sport Design kit (Ducktail) do you also get the "Wing" that goes up at speed? I have an X51 991S Cab coming with the Sport Design kit and find this interesting. There haven't been any Sport Design optioned cars arrive at the dealer in Vancouver yet (nor even ordered other than mine) so I can't check it out at the dealer.

rosenbergendo

I have run many laps with my best bud's 991 with PDCC, PTV,SC, and MSS. He is nowhere even close to me (997.2 GT3) on either PBIR or at Sebring. I can catch and pass him quite easily on both tracks. Maybe the Powerkit will make a difference? I cant imagine a 991 is even close to an RS. I know Porsche's Ring times said they should be, but all the Euro magazines like SportAuto havent gotten any where close to their Gt3/RS times.

chuckbdc

Porsche listed times at the 'Ring that had the 991S (on its street tires) as fast as a GT3 on R rated tires).

I thought the RS had more HP, suspension goodies, stiffening and better rubber than the GT3 and so was going to be substantially faster. They sure look the part!

Dr.Bill

No, just the ducktail spoiler. The added wing is fixed and is part of the aerokit.

The local dealer has one on the lot:
http://scottsdale.porschedealer.com/...81439/info.php

They also recently had a powerkit cab with the ductail spoiler. I guess it got sold. I took that one for a test drive. It would have been an awesome GT car!

FastLaneTurbo

Comparing the Aerokit Ducktail plus Wing on GT3inTX White car, it appears similar, if not identical, to the latest "spy" photos of the 991 GT3 Rear wing. Wings on cars get their downforce from the Vacuum created by air passing over Convex surface on the bottom of the wing "pulling" the wing down rather than pushing it down from the top, the reverse of airplane wings. The Ducktail below the wing acts as an airdam forcing more air between the wing bottom and the ducktail and accelerating the airflow, and thus the effective downforce. I modified my 1995 993 TT GT2 Factory Race car adding a second wing to create a similar airflow pattern and was amazed at how much of an increase It gave me on downforce.
The new Aerokit / GT3 wing configuration should be extremely effective.

FastLaneTurbo

Perhaps you are a better driver than your best Bud? GT3 Times are very close:
w/o Pwr Kit 991 C2S GT3
Nurburgring 7:37.9 7:40
Mireval 1:33.14 1:34.00
Bedford 1:22.8 1:23.3
Laguna Seca 1:39.3 1:39.52

I agree that on most tracks, the GT3RS is 1-3 seconds faster than both
the 991C2S and the GT3, but the GT3 and 991S are very closely matched
even with street tires on the 991. I would expect the new 991 GT3 to be
several seconds/lap faster than the 997 GT3RS.

ArashApollo

Correct! Fluid dynamics 101

dasams

Which also tells us there's a trade-off between downforce and top speed. I'd love to see Porsche documentation about what, if any, top speed is lost when the aerokit is specced in combo with sport design. That has got to have more drag than sport design sans the wing. dave

DrJay

I may get flack for asking this considering fuel economy is not the most important factor in the purchase of a 911, but how much of a hit to the fuel economy does the ducktail create? What is your best guess?

chuckbdc

I know from direct experience that ducktails reduce lift and drag. I put one on a 1974S (along with a front spoiler lip) and together they generated a very obvious stability improvement in a fast downhill curve in particular, and slight increases in straightaway speeds on the track I frequented. I don't recall Porsche suggesting that it generated downforce- killing lift was the thing at the time.

But a 1974 911 is far less aerodynaminc than a 991, and generated a lot of lift at the rear starting at speeds over 75. Moreover the standard 991 spoiler when deployed, has a lot of surface area and angle, so the comparative effects should be smaller.

So a guess- the ducktail spoiler is purely ornimental below about 80mph with respect to downforce and drag reduction, may lower drag enough to notice better fuel effeciency compared to one with out it to about 100, and beyond that the proportion of effect so sharply decreases as a factor in fuel consumption that is would be lost in the wind, so to speak.

DrJay

That's very interesting to hear, thanks for sharing.

Bigfra

Priced up retro fitting the x51 kit at Porsche Glasgow today. won't achieve peak performance until 6750 miles or so and will cost in the region of £9500 and that's if you already have the sports exhaust so roughly $15350 in yank money. Not f*ckin cheap for 30 bhp but at least it keeps the warranty

chuckbdc

At that rate the standard 400 HP car should cost $204,400. Makes the S look a bargain!

(OK OK I know horses beyond i.75 HP/cubic inch require extra grooming).

Bigfra

Good way to look at it

ny991

Just to be certain, the ducktail does not deploy like the standard spoiler? From what I see here it is fixed and does not move regardless of speed?