Bill Lehman

I just returned from Watkins Glen after testing my Low wing angle with APR Gurney flap. Here's my speed data. The Blue line is High Wing angle and No Gurney (my fastest lap set last August), The Orange line is High Wing angle and Gurney flap, The Green line is Low Wing angle and Gurney flap. The cursor is set at the end of the front straight and the high speed shown is at the end of the back straight. Weather conditions were similar. The faster speed were set with old Hoosiers, the slower on much newer Hoosiers. I'm no pro so there could be driver inconsistencies.

Reborn996

Bill, not familiar with that type of graphing... can you share a layman's interpretation of which setting was best?

Bill Lehman

Generally aero devices such as wings add downforce to increase cornering speed. The trade off is that they add drag and reduce speed. My data would be easier to understand if I had only posted the speed graph but there could be value in seeing if Lateral G forces were higher with the additional aero bits. The Gurney flap is an addition to the trailing edge of the wiing which is supposed to add downforce with little additional drag. If you look at the speed graph you see the speeds of the car as it does a lap of the track. My speed at the end of the long back straight at Watkins Glen was 145.3 mph with the high wing angle and no Gurney flap compared with 141.4 mph with high wing angle and Gurney flap. On the shorter front straight the speeds were 133.6 vrs 130.9 The green line is low angle of attack with Gurney and speeds were similar to high angle of attack without Gurney. What this seems to show is that using a Gurney flap with high wing angle reduces speed on the straight and does does not add additional downforce to improve corner speed.

Reborn996

Thanks for the clarification Bill, the reason I was asking is I have the APR Gurney flap and the wing at high angle (along with Salter Aero risers) and was wondering if I should put it back to low angle setting. Sounds like that would be a good idea from your analysis which would allow me to keep straight line speed with no noticeable decrease in downforce for cornering.

Bill Lehman

I'm planning to remove the Gurney flap and run high wing angle on tracks with very fast corners (90 mph+) and try the low wing position with no Gurney on slower corner tracks. This thread started out about the gains made with the wing risers. I'd like to see that data, it certainly lets the wing get into cleaner air and most "real" race cars use a high wing.

mousecatcher

1.82 vs 1.69 lat g

aryork

Great thread, and I LOVE the CFD plot of the GT4!

ShakeNBake

Bill, that's really interesting info on the Gurney flap. I am going to attempt to do a test at COTA depending on how busy I get. I have way too much rear downforce right now, the car is pushing badly through 17-18.

Bill Lehman

The high Lat G corners tend to be the slow tighter corners where there is little aero downforce.

ShakeNBake

I didn't get data, but I was mostly looking at fixing a handling imbalance I introduced with upright extensions (bbi). My car has extreme high speed push on T17 and T18 at COTA since I added BBi uprights. After a ton of alignment changes, we've not been able to tune it out. So I tried playing around with the wing. I was running he highest angle and a gurney flap. Clearly too much cow bell. No gurney and the lowest angle was better, but it still pushes a bit. Higher top speed in the straights, but needs more data. Uprights clearly adds some downforce.

Bill Lehman

I've removed the Gurney flap and just swapped out Tarett rear toe links for TPC and am trying less rear toe. Next outing will be Summit Point which has slower corners than Watkins Glen but some long straights. I'll try high and low wing angle and collect data.

Phi19

I have just seen this thread. Very cool and interesting CFD, I am also very interested since I am also using Salter Aero uprights which IMHO are the best in term of look and probably efficiency as I think they give the best balance between height and distance increase towards the tail of the car as well as closest setup wrt GT3RS wing configuration. I recently did a trackday at the Nurburgring GP track and found the car with really good balance in fast corners, but I can not state the difference with OEM uprights as I did not test both on the same track. I am mostly wondering whether with this setup I should really remove the front flaps to increase downforce on the front while I haven't noticed more understeer than formerly, and knowing that it will be detrimental on the max speed. Anyhow I have largely compensated the loss of max speed with higher wing (if any) by installing Fabspeed Race Headers, full lightweight race exhaust line and BMC air filters, so my GT4 is breathing with full lungs :-)
This said, I am not a race driver, I reach my limits before the limits of my GT4 on track, but my car has been driven by a Porsche instructor who found it fantastic and he even managed to overtake several GT3, GT3RS, Nissan GTR Nismo which are way more powerful.... anyhow, awesome experience at the Nurburgring GP track. Nordschleife is way too dangerous for someone like me...

Am I wrong or from your CFD, I would conclude that the OEM rear diffuser is not functional at all ??

Verus-Paul

I'm the same person as plucas, just became a vendor so posting under a new name for your reference.

You might not notice anymore understeer as you might just like the feel of a more rear biased car so you drive it better. Would adding something like dive planes / canards on the front improve the feel and times around a track? That would be very hard to answer as it really depends and I could only answer about our parts. Our dive planes add a good amount of downforce, 90lbs at 120mph with a small drag penalty of 17lbs. These will shift aero balance forward, but more forward to make the car feel more unbalanced to you, that I do not know. The only way to really find out is to try them out and see, but that cost money and might not improve your times. I would say it is up to you on that. One benefit our dive planes have though is that they direct more air to the engine inlet ducts to improve airflow to the engine. If you want to know more on that, see our specific dive plane thread here

The OEM diffuser is not functional at all. It is for looks, and I hate to even call it a diffuser at all. It is more of a bumper cover to make the backend look nice. It isn't a diffuser in the way a motorsports diffuser is or like the one we are coming out with is.

Phi19

Ha! Ha! now I understand Paul, as I was indeed talking to you on the other thread about the dive planes. For the latter, you have fully answered my questions.
May I ask you a similar question whether you have a CFD airflow comparison or quantification of increased downforce or airflow quality between this wing configuration (I understood with Salter Aero uprights) and OEM configuration (with OEM uprights)? ... and comparison with your Mega Wing under development?

Finally it would be appreciated if you could share what are the main drivers and performance expectations which lead you develop your current Mega Wing (similar to Cup Cars) and active diffuser for the GT4.

Verus-Paul

I do not have a comparison of the factory to Salter uprights as the car that was scanned (Dundon Motorsports car) already had the Salter uprights. I could compare our wing to the OEM wing at the Salter height though fairly easily. I just haven't done it yet. I will get all that ready when we release the rear wing kit for the GT4 though.

Drivers and Performance Expectations for the Verus Engineering Wing:
Sorry if this gets too detailed for some, but I want to make sure I am as thorough as possible with my explanation. First, the main goal for us is always efficiency. What I feel sets us apart from others is the fact that we put a lot of effort into proper R&D on the aerodynamic side and one way that is shown is with the efficiency we get out of our aero parts. Efficiency is just another word for L/D or the relationship of lift over drag. In motorsports, this number is negative because we are looking at downforce, but we just use the absolute value of this. We want to make as much downforce as possible without it becoming a detriment in drag. This was first done in 2d and starting with an off the shelf profile as there are thousands of them. From there, we ran optimization metrics to improve L/D values by morphing the airfoil profile. This was done using the adjoint solver in ANSYS Fluent. Basically, the adjoint solver finds sensitivities on the surface for values we specify. Since we are looking at downforce and lift, we set the solver to look for sensitivities on the surface of the airfoil which affect these 2 key areas. From there, we set goals within the software and iterate. We did this at multiple Reynolds numbers that a wing would see on the track and at multiple angles of attack. During this part of the development, we also set out to have a convex recovery on the underside of the wing. Convex recovery basically means that when the wing stalls, it is a trailing edge stall. A trailing edge stall is preferred as you do not have a massive drop in downforce when the wing stalls. Say you have a heavy braking zone and when you brake, the wing stalls. If you have a trailing edge stall, very little downforce is lost which is why it is also known as a soft stall. If you have a leading edge stall, you will lose a large amount of rear downforce under heavy braking which could lead to very unstable or a car which crashes. I spent about 6 months on this aspect of development as we use this profile on a 3d wing also.

From the 2D CFD, we moved to 3D. This is where the downforce goals became the deciding factor. We knew based on some initial 3D testing, we wanted to be in the 250-300mm chord range. We decided on the larger chord of 300mm. This would allow the wing in most classes that limit chord length. It would also allow a good amount of downforce and we could limit the amount with wing angle choice and span. We can make the span at any length up to 1950mm. The 3D CFD helped us verify the trailing edge stall and start figuring out where the final numbers will lead to. We then moved onto optimizing endpates which we did both in free-stream and on the car to make sure the endplates were functioning properly. We probably spent about a month just developing the endplates by refining and optimizing. After the endplates were finalized, we ran the wing through all the angles of attack for final performance numbers at different spans. Also somewhere in the 3D phase we also figured out the optimum gurney height for the wing if the customer wants to install it.

From this CFD model concept, we went to the manufacturing model. This is where we relied on a carbon manufactures expertise on the internal structure and we worked with them during manufacturing to make a super strong and lightweight part. The entire wing at 1800mm with endplates weighs right at 8lbs. Overall a lot of work went into the wing development. I can go into further details in specific areas if you have further questions. Hopefully that answered that question.

On the diffuser question, are you talking about the rear of the front diffuser (our front splitter kit has front diffusers).