TB993tt

Based on Porsche's quote of 60% more downforce than regular GT2 and using Sport Auto mag's independant GT2 wind tunnel test numbers we have:

911SLOW

Very nice work! Wish you could add gt3 rs numbers to compare then it would be easier to guess its downforce from experience. Also to confirm what Porsche said about almost equal downforce with the gt3rs.

John

GTSilver

What are the differences between the 997.1 GT2 and 997.2 GT2RS rear spoiler ? aren't they identical, they seem to be.

sansh2o

Might have more to do with changes to the rear facia treatment/diffusers.

Z06

I am in! When do you think we will be able to order these parts?

Riz

I think they said it has less downforce that 997.2 GT3 RS.

911SLOW

Chris Haris "Aerodynamically, it’s quite similar to the 997 GT2, but runs a new splitter, new rear diffuser and an extra gurney on the rear wing. Doesn’t sound like much, but it nearly has as much downforce as the GT3 RS"

John

TB993tt

Here you go....



Bare in mind with the above that the GT3RS numbers of from the Sport Auto independant test in the Mercedes wind tunnel, the GT2RS numbers are extrapolated from the SA test of the 997GT2 with 60% added on as per the stated "extra downforce" to the press - presumably Porsche meant 60% extra onto their numbers..... regardless 60% is 60% so it should be correct.

The GT2RS has some amazing numbers for such subtle spoilerage....

911SLOW

Little bit of creative thinking here but the number should be close to the real deal. Also we don’t know about the front yet because the 60% you quote I think was for the rear and it matches the 60% larger wing surface area I read about.
I would like to see a picture from the top and compare it with the 2008 to see if that confirms visually.
Great post nonetheless

John

TB993tt

The surface area is not 60% greater Edit actually it is probably the gurney which is 60% bigger ! it is a very subtley bigger (10mm I think) gurney which protudes with slightly more angle, but hard to tell the difference from the pics.... Manthey offer a similar bigger gurney replacement but only claim 8kg extra downforce or so.....
It is the front splitter which appears to be making the difference and of course how that works in conjunction with the new rear gurney shape appears to give these awesome numbers but at quite a severe drag penalty of Cd 0.34 vs 0.32 (bigger front tyres/wheels/arches also contribute) - amazing how such subtle differences can work

911SLOW

^
From the press release: http://www.porsche.com/uk/aboutporsc...&id=2010-05-12
How on earth 1 cm adds so much downforce? Strange.

John

C.J. Ichiban

shape and placement of the aero parts has just as much to do as size at the trailing edges of these things...if something is completely vertical vs slightly angled that makes a much bigger difference even if they're the same size parts

911SLOW

CJ i see your point but if we take for granted that the only change is the sitting higher by 1cm it is weirf that it amplifies the downforce by that much.
So maybe we are missing something from the aero facts of the gt2rs.

John

Jean

For future reference...Since it happens that I have the GT2RS Sport-Auto test in hand, the numbers are not too far from TB's calculations..here they are:

Downforce Numbers:
At 200kph (124mph): Fr 14Kgs, Rr: 35Kgs
At 330kph (205mph): Fr 25Kgs, Rr: 142Kgs

Front Area: 2.06Sq.M.
Cd: 0.35
CDxA: 0.71

Forgive me if this has already been posted elsewhere on this forum.

TRAKCAR

So, I would have 60% more downforce with my 10mm Gurney flap on the GT3RS?

Sounds like a lot but I believe it, I could really tell the CUP front lip and Gurney flap in the same conditions, within the hour on the same track...