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Theoretically speaking all other variables being the same, lift is proportionate to the wing area.
GT2RS wing area ~0.44 Sq.m
New wing area ~ 0.56 Sq.m => increased downforce 27%
Here is the data for the wing (not full car downforce) at max Angle:
Impact of Angle of attack @ 100Mph
I also designed custom wing uprights that are higher by about 2.2 inches, have a more pronounced rearward angle, and has adjustments from 0-17 degrees angle of attack possible. Also larger side plates and added a 15mm gurney.
GT2RS upright vs. new uprights:
To balance the front added a splitter (see picture on previous post above), also added a GT2RS diffuser as well.
I have not tested this new setup given the ongoing circumstances.
But with the GT2RS bodywork (front bumper and rear wing only) on a rather fast F1 circuit 5.4 miles configuration, I improved my lap times by over 2 seconds and took the circuit lap record. Part of that gain is because last year I ran with a partial limp mode. So based on my datalogs, the net aero impact from GT2RS front bumper and rear wing (no fender louvres and no rear diffuser) was about 0.5-0.7 seconds on a 2:07s lap time.
Great stuff man! Your hard work and hard earned money definitely doesn’t get unnoticed.
I’ve been back and forth with a few fab companies and I’m getting mixed opinions of designs of the uprights. One says your design (Pic 1) creates a bit more drag compared to a solid upright (Pic 2). What is your take on it?
With that said, if you intend to track these cars i would be very cautious of this much down force and increase in drag while solely relying on the stock mounting points. There is a reason why all of Porsche race cars uprights sit on the frame and not attach to the decklid. I believe Jean took other measures to make sure his use would be safe.
Micky360, I suspect the drag impact is negligible. I wanted to keep the stock look of the uprights. Otherwise the GT3 cup solution is perfect, although not very high quality.
Pdtp, this Dundon kit is really great..! The swan uprights are a nice addition and have more efficient Lift/Drag ratios. I love the products they put in the market and they support it with CFD data, Only downside I see is the price, considering it cost me 1/3 of that and I am using top quality CF and wind tunnel tested larger wing and splitter.
You make a good point about high downforce, brackets need to be reinforced or bolt the rear wing to the frame. Also the suspension needs to be much stiffer, so whoever wants to go this route needs to know that the expense is much much greater than it seems to have a balanced car. I actually would not recommend any of this unless one has the addiction of testing and finding the limits of the turbo on circuit. It all doesn't make much sense.
Micky360, I suspect the drag impact is negligible. I wanted to keep the stock look of the uprights. Otherwise the GT3 cup solution is perfect, although not very high quality.
Pdtp, this Dundon kit is really great..! The swan uprights are a nice addition and have more efficient Lift/Drag ratios. I love the products they put in the market and they support it with CFD data, Only downside I see is the price, considering it cost me 1/3 of that and I am using top quality CF and wind tunnel tested larger wing and splitter.
You make a good point about high downforce, brackets need to be reinforced or bolt the rear wing to the frame. Also the suspension needs to be much stiffer, so whoever wants to go this route needs to know that the expense is much much greater than it seems to have a balanced car. I actually would not recommend any of this unless one has the addiction of testing and finding the limits of the turbo on circuit. It all doesn't make much sense.
yes it is pricey. I was very surprised. Came onto it today trying to look for front floor mounts on the .2 Cup with Simon today. Good data though and I’m sure it’s top quality.
Jean,
Appreciate this post greatly! Makes an aero eng. happy to see! I saw the GT underbody diffusert for sale via Suncoast... wondered what it took to fit it and if this would/should be the first add on for aero for the 991TT with wider side skirts to keep underbody flow accelerated and pulling down at speed. Any ideas on the numbers from these?
Jean,
Appreciate this post greatly! Makes an aero eng. happy to see! I saw the GT underbody diffusert for sale via Suncoast... wondered what it took to fit it and if this would/should be the first add on for aero for the 991TT with wider side skirts to keep underbody flow accelerated and pulling down at speed. Any ideas on the numbers from these?
As an aero engineer you know exactly what you are saying The most efficient aerodynamic part of a race car is the diffuser and flat bottom, highest downforce/drag ratio. I read some time back on some technical document that the 911R doubled its downforce thanks to a specially made diffuser.
I ended up buying the GT2RS Porsche engineered diffuser after many failed attempts of building a custom CF diffuser with a specialized shop, heat management and lack of guaranteed result made me drop it. To fit the GT2RS diffuser you need the brackets and diffuser, both sold by Porsche or Suncoast or others.
I would definitely go for a diffuser before anything else on a stock turbo. The side skirts are more for show and not really efficient as they're not really sealing the sills to the floor, they do help channeling air around the rear wheel.
Here is a very interesting video from Enrique Scalabroni, one of the world's top aerodynamicists explaining very easily the diffuser impact on rear downforce with water and a spoon, a must see.
Also a snapshot of a study done by Willem Toett, the Sauber F1 head aerodynamics engineer on their F1 car showing highest downforce being generated by the flat floor design and diffuser. An F1 car being so low, the effect is much higher than our cars of course but the principle remains true I think.
It is always interesting to watch someone who thinks in three dimensions explain something, versus most of our two dimensional thinking. Thanks Jean, very informative, and well beyond my mathematical skill set.
I assumed the same on the sides skirts (but hoped = cheap mod for both zing and bling).. My other concern was the stock suspension height may not be low enough to really avoid "spillage" and have the same benefits of the GT2RS
I've really been trying to figure out the best way to help carry more speed in long corners so want to keep it balanced. only so many variables - sticky tires (burns up faster), more downforce (always there), more contact patch (Camber/suspension changes). I don't like how that GT3RSs have another 15mph on me there.
It is always interesting to watch someone who thinks in three dimensions explain something, versus most of our two dimensional thinking. Thanks Jean, very informative, and well beyond my mathematical skill set.
Thanks 2fcknfst, all this is borderline boring actually, and of very little use to almost anyone, but could one day help someone save a penny by making informed decisions.
I assumed the same on the sides skirts (but hoped = cheap mod for both zing and bling).. I don't like how that GT3RSs have another 15mph on me there.
I know what you mean, not fun seeing GT2RS and GT3RS making it seem easy while we are holding to our lives.. But weight rather than downforce is your biggest enemy in those long fast corners, the inertia you are subject to is much higher than the lighter cars.
01-27-2020, 08:07 PM
