Porsche 911 GT3R aerodynamic drag influenced by rear wing settings

Hi!

I have issue with Porsche 911 GT3R 2019 rear wing aerodynamics drag depending on wing settings.
With rear wing max. settings top speed on Paul Ricard was 269,9 kph. Than I set up to rear wing to min. drag and top speed was 271,4 kph. So difference was only 1,5 kph. I think It should bee 10x bigger difference.


Rear wing on Porsche 911 GT3R 2019 is one of biggest in GT3 class because of cars architekture . So rear wing setting must have big impact on car top speed.

I have a realistic 3d model of that car.So I will make CFD simulation on this car how does rear wing setting influence aerodynamic drag. If anybody is interesting I will share my results.



I will use OpenFoam for CFD calculation. Results will be aerodynamics forces (downforce, dragforce and aero ballance).I will do it for min. and max. rear wing settings.
Then I will put those results to Bosch LapSim simulator to calculate top speed on racing track.

 

Statement does not logically follow.

 

Thank you Alex for response.

Porsche has much bigger wing. Its chord is 390mm and span 1900mm and it has 15mm gurney flap on it. So forces from such a big aero device must be much bigger than on APR 250 profile.


From CFD simulation for this wing alone CDA for wing is 0,140 at agle of attack 5deg in centerline and near endplates 11deg. L/D for this setting is around 10.

 

Out of interest, which single part of the car generates most drag? Would it be tyres, front splitter then mirrors maybe?

 

I found "real world data" for Porsche Cayman 987 by Verus engineering for comparison.
Car features single element rear wing 1900x300mm, spront splitter with diffusers, dive plates and rear diffuser.
So aero features of this car a more or less like GT3 cars but not as much refined.
Verus engineering gives us aero data of their car.



From that table I calculated for:

Rear wing AoA 0 deg : CDA=0,851
Rear wing AoA 10 deg : CDA=0,944

and inserting in LapSim and go to test at Monza:


Results for RW AoA 0deg - top speed is 277,0kph
Results for RW AoA 10deg - top speed is 271,3 kph

So you can see 5,7kph speed difference. And that car has only 300mm chord wing and with no gurney flap.
Back straight in Paul Ricard is longer than in Monza S/F straight difference in top speed will be bigger there too.

 

It is not GT4 car. It is tuned GT4 car with more aero like GT3 cars.
Also i pluged 500hp for engine to be more like GT3 car. So actually it represents GT3 car with Cayman 987 Verus tuned car.
From that perspective simulated top speed 277kph is in GT3 region.

I also have old Ferrai 458 GT3 car wind tunell test from racecar engineering and will post those numbers later.

 

Here is aero data for Ferrari 430GT3
Wing at 0 deg, CD=0.463,CDA=0,926
Wing at 9deg, CD=0.540,CDA=1,080
Data come from racecar engineering july/2010
and that include rake change .
So delta CDA is 0,154 when comparing min. downforce setting to Max. downforce setting.
Your Can see that delta is even bigger that on Cayman 987.
Wing used on F430GT3 was used by Ferrari 550GT1 back in the days.
Dimmension of wing is 2000x400.



In my simulation i will do some test with rake change and how it will affect aero forces too.

 

And another example of AMR Vantage GT3 from racecar engineering magazine.

Rear wing of that car has 3 settings. Max is 16deg and min is 11,5deg (which is quite extreme). Dimmension of that wing is 2000x370mm
They cant show absolute value only percentage of change of forces.
So you can see that 4,5deg of rear wing change make 6,9% of total drag. If CDA of that car is 0,9 , detla CDA would be 0,062 and that with only 4,5deg of rear wing change!

Later today my simulation of Porche will be done so I will post results. I´m testing rear wing in 3 positions - 0deg, 5deg and 8deg. So I avoid extreme settings.

 

It differs very much depending on what type of car you're looking at.

F.e. on a F1 car it's the rear wing (~30%), followed by the rear wheels (~20%) and front wheels (~15%) that create the most drag. But of course that's mainly due to the fact the rest of the bodywork is so streamlined it barely produces any.

 

So my CFD simulations are done and here are the results for Monza track:
Car spec: 529hp, 1375kg (1295kg+80kg) based on BoP 2021 for VLN series

Porsche rear wing AoA 7deg - baseline set up, top speed 268,3 kph
Porsche rear wing AoA 0deg - delta CDA = - 0,116, top speed 274,6 kph, delta rake angle +0,15deg due to less force from rear wing



So my next simulation will be with rake change of 0,15deg (more rake angle for rear wing AoA 0deg) to see effect on top speed