GT4 Wing Development pt1

GT4 Wing Development pt1

March 03, 2020

We've been working on designing a new wing for the GT4 to significantly increase the overall downforce production in the rear of the car. But how did we end up deciding to design and build an entire new wing? We're going to take you a little bit on our development journey because there are so many ways to do this and a few options already already exist out on the market. Today we will go over wing angle of attack changes and wing heights.

1. Wing AOA (Angle of attack)

First up, let's take a look at increasing AOA. We wanted to explore this as a feasible option because of the simplicity of reusing the OEM wing. All we would need to do is design is a different wing mount and voila! Instant downforce without much increased cost! Or is it? Here are the approximate downforce numbers and corresponding drag relative to the 1deg setup on the OEM rear wing from our CFD analysis. The CFD was run at 80mph at the stock height. We choose to do most of our tests at 80mph because the average turn speed at the track is around 80mph. This will show us what you can expect on most turns.

1deg: 42lbs/ ~5lbs drag

3deg: 44lbs/ +1lb drag

5deg: 45lbs/+2lb drag

7deg: 47lbs/ +4lbs drag

9deg: 48lbs / +6lbs drag

11deg: 49lbs / +8.5lbs drag

So as we raise the wing AOA, we do see an increase in downforce but also an increase in drag. Here we can generate almost +9lbs at 11 deg AOA which is ~22% increase in downforce. Even though there are gains in downforce from running 11deg, the increase in drag levels is quite high. This is actually a sign of boundary layer separation at high AOA and you can see that we don't get a good efficiency tradeoff for downforce and drag. We can clearly see that the wing was never designed to run at such high AOAs. The optimal gains would probably be around 7deg AOA. A final note on the OEM wing is that the wing was designed to produce very little drag and not much downforce. 

2. Wing Risers

So far I don't believe anyone has released information on the effect of wing risers on downforce. Everyone has just speculated about the cleaner air but no one has actually shown the CFD analysis. Here are the results at 5deg AOA, 80mph, and 100mm increased height.

OEM height: 45lbs

+100mm height: 51.5lbs/ +0.5lbs drag (vs. OEM height)

We can see a small increase in downforce of 6.5lbs from raising up the wing just 100mm (~4"). This is about +14% increase in downforce with almost no increase in drag. Wing risers are not a bad way to increase downforce but even with the increased height and AOA, the net results only add +10-12lbs of downforce. Throw a 10 lbs weight into your trunk and see if you can notice the difference when you take an 80mph turn. I know it's not the same but that's kind of what you should expect when you raise the wing and add a little bit of AOA.

Next up... we'll explore gurney flaps and how they increase downforce on the GT4 wing!


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