Difference between gtc 200 and gtc250 apr wings

[rueyme]

Does anyone have any opinion the difference between the gtc200 and gtc250 wing for the z4m coupe? I notice apr now only lists the gtc200 for sale on their website. Please let me know the difference if there is any major diff.

[TRiCC]

The gtc200 is a “3D” profile/plane and the gt250 is a “2D” profile/plane

[rueyme]

Originally Posted by TRiCC

The gtc200 is a “3D” profile/plane and the gt250 is a “2D” profile/plane

thanks for the reply. I assume 3d profile is more modern and efficient?

the GT250 seems more costly however, so I'm wondering why the 2d is more expensive.

[Azeka1]

Disclaimer: I am absolutely no expert in this stuff and can only go off of my personal experience and research.

I currently run a GTC200 "3D Profile" and I find that it is a great entry level wing for mild downforce. It offers good adjustability and pairs well with a smaller front splitter (< 2" out from front bumper). With an APR front splitter, I currently run 4* AOA without a Gurney Flap and find the car has a slight push at corner entry but balanced through mid and exit. New suspension going in this year so this could change.

- A 3D foil will be more efficient at lower speeds with a low AOA (less drag & more downforce) compared to a 2D foil. However, if you try to get higher downforce from a 3D foil with a high AOA, it will be less efficient than the 2D with a much lower downforce ceiling.

- A 2D foil - like the GT250 - will give you much greater amounts of downforce at higher AOA with less drag.

In short: if you plan to run streetable front aero (ie, APR splitter) the GTC-200 will balance well. If you plan to run higher front downforce with a >2" splitter and dive-planes, go with the GT-250 to efficiently balance the rear.

To put it all in perspective, review this document comparing Downforce and Drag figures.
https://www.evolutionm.net/forums/at...ison-chart.pdf

[rueyme]

Originally Posted by Azeka1

Disclaimer: I am absolutely no expert in this stuff and can only go off of my personal experience and research.

I currently run a GTC200 "3D Profile" and I find that it is a great entry level wing for mild downforce. It offers good adjustability and pairs well with a smaller front splitter (< 2" out from front bumper). With an APR front splitter, I currently run 4* AOA without a Gurney Flap and find the car has a slight push at corner entry but balanced through mid and exit. New suspension going in this year so this could change.

- A 3D foil will be more efficient at lower speeds with a low AOA (less drag & more downforce) compared to a 2D foil. However, if you try to get higher downforce from a 3D foil with a high AOA, it will be less efficient than the 2D with a much lower downforce ceiling.

- A 2D foil - like the GT250 - will give you much greater amounts of downforce at higher AOA with less drag.

In short: if you plan to run streetable front aero (ie, APR splitter) the GTC-200 will balance well. If you plan to run higher front downforce with a >2" splitter and dive-planes, go with the GT-200 to efficiently balance the rear.

To put it all in perspective, review this document comparing Downforce and Drag figures.
https://www.evolutionm.net/forums/at...ison-chart.pdf

thanks for the simple to understand explanation and breakdown. When you say lower speeds, assuming I'm averaging around 110 max and around 70-80mph throughout the track that is more like low speeds vs the higher speed setup?

I noticed you have the GTC200 on your car and the APR front so I am going to get the same. I wonder how much of a difference btw, we're talking about in terms of additional downforce at higher speeds between the two models. And is there any way for it to be calculated outside of computer simulated models?

[Azeka1]

Apologies, saying “lower speeds” was probably not the best way to put it. It really comes down to angle of attack and the amount of rear downforce you need to balance the front of the car.

The Gtc-200 begins to get less efficient as you approach the 8* range and caps out at around 260 (without a gurney flap). The GT-250 is capable of producing much more downforce efficiently at higher angles.

Unsure of other ways to test this aside from real world trial and error. Hope this helps and maybe someone with better knowledge on aerodynamics can chime in.

[Finnegan]

Great discussion! I was just about to ask the same questions. Thanks for the insight!

[Vanne]

Gurney flap is a great idea and a must have.

[Michael9218]

The design idea of the 3D wing is to equalize the AOA of the air coming over the roof line. On a wide wing (full body width), especially on a sedan body shape, the airflow out at the ends of the wing will be different than the airflow coming off the roof. The higher you mount the wing, the less this is a factor. At best, wings like the APR are guessing at where this transition takes place, and of course, it will differ for every car shape and wing placement, which they don't accommodate. If not done right, you end up with a wing with mixed angles of attack. This will result in suboptimal lift and excessive drag. Given the coupes sloped roof line and unless you plan to run a wide wing (70") low on the deck, I would say the 3D wing would be less effective than a 2D wing.

[rueyme]

Originally Posted by Vanne

Gurney flap is a great idea and a must have.

where can I get one?

thanks

[Azeka1]

Originally Posted by Michael9218

The design idea of the 3D wing is to equalize the AOA of the air coming over the roof line. On a wide wing (full body width), especially on a sedan body shape, the airflow out at the ends of the wing will be different than the airflow coming off the roof. The higher you mount the wing, the less this is a factor. At best, wings like the APR are guessing at where this transition takes place, and of course, it will differ for every car shape and wing placement, which they don't accommodate. If not done right, you end up with a wing with mixed angles of attack. This will result in suboptimal lift and excessive drag. Given the coupes sloped roof line and unless you plan to run a wide wing (70") low on the deck, I would say the 3D wing would be less effective than a 2D wing.

Thanks for the very helpful insight!

rueyme APR sells them on their website.

[rueyme]

Originally Posted by Azeka1

Thanks for the very helpful insight!

rueyme APR sells them on their website.

Yes I noticed they sell the model but not the one meant for our cars anymore. If you look at the car application only the 250 is available for z4m coupes.

[Azeka1]

Great video by AJ Hartman -FKA RHR- (manufacturer of Michael9218’s Wing) comparing 3D and 2D wings in a wind tunnel. Extremely informative!

[Michael9218]

Thanks for posting. Excellent video from RHR. Cuts through marketing hype and shows actual performance!

I can tell you that with their wing you can feel the difference in AOA. I run mine at 0 relative to the ground unless wet. I turn it down a few degrees in the wet and you can feel the improvement in rear grip.

[Michael9218]

Also note that their reference point for AOA is the ground, which isn't the aerodynamic AOA. He discusses this towards the end of the video. Looking at the image below of a Z4 coupe, you can see the air stream is at 3-5 degrees downward angle depending on your wing placement. So while it may look odd, a wing turned up will still make downforce. It would've been interesting to see the results if they had put the wing at -5 degrees AOA relative to the ground.



Also worth noting the impact of the Gurney flap. Basically provides "free" downforce. Meaning little drag penalty for the increase in downforce. My only criticism of their Gurney flap is that it is too large. Most sources suggest it should be 1-2% of chord. So on their 14" wing, the Gurney flap should be 1/4", not 1/2". Would be interesting to see what this difference would make.