James88

Lots of good info here.
I'll be doing a track day soon with mainly slow corners and one fast one and two long fast straights.
Last time I was there, a 981 spyder wasn't far behind me, there wasn't a lot of difference in straight line speeds.
I'm considering putting the front blocks back in and rear wing back to less downforce.

paradocs98

Viperguy324

I also see a loss of roughly 5kmph into turn 1 on the NurGP track. That said, I do not have to Lift in the MS-S T9-10 (Reduced Both understeer and a slight walk I had without aero)... So the increase in height and dive planes are doing their job. Also noticed less understeer in the Val-K T6.

Current setup
Front flaps removed
Dive Planes
Increased rear wing struts

Reborn996

Wonder if we could get the details on the analysis results for the addition of the gurney flap on the clubsport wing? Would be interesting to see...

plucas

Not sure on this wing the gurney and without gurney performance. It wouldn't be too hard to find out. Also, not all gurneys are the same. I have seen some wings that are very sensitive to gurney height where even 1mm taller increases drag a good amount without any increase or even sometimes a decrease in downforce.

With uprights. Remember that lifting the wing might not create a more downforce, but still could make the car unbalanced. The higher the wing is on the car, the higher the drag moment is on the rear axle (acting in the direction that would lift the front). A great way to tweak aero balance with components is to move them and adjust the moments they create.

It is because most people can't run proper CFD analysis. It is a skill that takes years and years of work to become competent at usually with the help of university. It is also very expensive, especially from the software and hardware side. We use ANSYS Fluent and I know a year of that software cost $35k which can then increase depending on how many HPC licenses are needed. I also know OpenFOAM which is free but much more difficult to use to get meaningful results. Hardware is a totally another animal that can get very expensive quick, especially with the size of models in the automotive field.

I can get this information if there is enough of a want. I would just need gurney heights and I can test that without a problem. I can run each problem in about 1/2 a day.

Bill Lehman

I dropped my Gurney flapped wing to it's low position this morning. I tried to measure angle of attack before and after. Measured 3 degrees in low position and 4 degrees in high position. These numbers are based on simple tools and my memory of trig. The height of the APR Gurney Flap is about 14 mm .I'll be trying this at the Metro NY DE @ WGI in about 3 weeks and will report any findings from my data.

plucas

14mm seems way too tall for the gurney flap on this wing. According to my CAD, the wing's chord is ~260mm which means the gurney should be anywhere from 3-10mm based on my past work and 10 would most likely be large also. I have also found some 3d profile wings like the factory wing do not perform better with a gurney but that has been the rare case. I would try and make the gurney around 6mm to start and see if performance improves.

GTS_Ninja

it's def not 14mm tall. Maybe you are talking about the mounting surface which is def wider than the height of the flap.

sigar

Cool thread.

Yargk

I was wondering about this as well. The gurney on the GT4 clubsport is quite large...

futurz

My 981S has the GT4 front end and a Getty GT3 replica wing in the rear. Higher than the GT4 but lower than some other uprights that are being sold.
The wing has the Dundon GT3 Gurney Flap which is 9.5mm tall.
The wing is set at 2.4 degrees. Any more than that I lose a lot of speed on the straights.
The car is very well balanced.
FWIW

Bill Lehman

The chord is about 260 mm and I agree that the Gurney flap looks too high. Attached are some photos, my height was measured at the back of the flap, first photo.

911tac

I'm running the APR Gurney on the Nordschleife and on Spa where I'm tracking regularly.
On the Nordschleife especially on the fast bumpy sections like Schwedenkreuz the gurney is one of the best improvements on the GT4.
In Spa which is a much planer tarmac and where the high power, fast sections are essential for laptimes it seems like the gurney together with the steep setup of the wing hurt more than it helps.
I'm planning on trying the flat wing setup together with the gurney on the next go.
In terms of balance i.m.o. the GT4 can use a lot more downforce in the back before the balance is starting to hurt.

Jamie@dundonmotorsports

We're working with Paul and Verus Engineering on bringing some science to the Porsche aerodynamic aftermarket. We suspect, like most things, Porsche had to compromise on aero for any number of reasons and bringing a complete kit out that adds downforce, preserves balance, is modular and upgradeable. We're working on a number of projects with them and wish there was more time in the day to get them all done!

Alan C.

Looking forward to seeing what you come up with.