[Phat Toni]

@GMS , I like that there's a carbon trunklid designed to support the wing instead of trying to strengthen the OEM one hoping it doesn't warp or crack.

Are there end plates in the works for this wing or a reason why this design wouldn't benefit from any?

 

[GMS]

We've been testing the wing and the hood quite a lot lately, even at speeds above 240km/h and so far so good. I still haven't decided on the end plates design yet as this is the part that is hard for me to make it effective and at the same time look right. Of course, the end plates are nothing but benefit on the wing as they reduce drag and increase downforce. They will be incorporated therefore, but are not key process at this stage of testing and development. Also, for some reason, the entire car, with wing on, but without end plates, looks less aggressive, than with them, so perhaps for the street, some, might even care to run without, as the ultimate drag and downforce is not what you are probably looking for on a street.

 

[4C-ophe]

Maybe the Germans can help you out. Were just released/spotted last week:

 

[GMS]

The idea of "Swan neck" wings (mounted on the upper side) is to reduce the air disturbance as the bottom of the wing is generating more downforce than the upper side of the wing, therefore also the end plates are always longer on the bottom side than upper side. Personally I'm not much of a fan of "Swan neck" mounting style as it requires bigger mounts which at the same time means more air disturbance (but on top), so the effect are somewhat diminished and for my taste makes the car look too "racey".

The mounts on that Cayman above are weird and too much angled, like toe out (following rear hood line). Probably it's just a render as I doubt the final design will be like that.

The reason the 911 series run such big wings, now even dual element, is that they can't equip an efficient rear diffuser as the engine right at the back. Probably next series will be MR (engine first and then gearbox) platform and not RR anymore (gearbox first and then engine) which will allow for proper diffuser among other benefits of MR vs. RR. They are just making slow transition, not to loose the die hard 911 fans and to send out new 911 version every 2-3 years, but they will eventually move to MR platform with 911 series, I'm confident in that.

BTW, here is a photo I've just received from a fellow Alfista in USA.

 

[4C-ophe]

Don't like swan necks either. Was more for the end plates I showed the pictures. I'm more a diffuser guy than a wing man btw.

The 911 in competition version (GT2 RSX2T5-i-don-t-know) has its gearbox and engine switched already.

Alfista for the States was on Facebook, and not many seemed to know where the parts came from (I pasted the links), but were very approving!

 

[GMS]

Hey Rudi,

Would you upload a picture of the view from the rear view mirror with the louver installed? I am curious to see how much it affects the visibility.

Thanks.

Sorry, I missed your post.

I can upload a pic, but it's not much to see and I rarely look back.

 

[Knievil]

Looks like Mikey Turbo upgraded his car on his latest video.

 

[4Canada]

For those interested in more technical aspect of this project here is some data from CFD analyze.

View attachment 121606

What speed generated these results, and do you have similar tables for other speeds?

 

[LP560-4C]

Duck tail / wing fan here. 3 for 3 in the garage right now, but one will soon be gone and replaced by a 4C spider............. NO 4C ducky 4 spidey ?

It's not going to ever be in the works for them ?

 

[GMS]

What speed generated these results, and do you have similar tables for other speeds?

160km/h, CFD analyze provided by the wing supplier. It's an UK based company that supplies wings for Ultima GTR and Lotus cars so I tend to trust them.

160km/h is somewhat average track speed for street cars so hence we used that one. On our track average speed is 158km/h with our 4C.

You can make out further rough estimations of relation between fownforce/speed according to this:

Duck tail / wing fan here. 3 for 3 in the garage right now, but one will soon be gone and replaced by a 4C spider............. NO 4C ducky 4 spidey ?

It's not going to ever be in the works for them ?

Maybe one day. We'd like to sort 4C's front end aero first (hood).

Fun fact - Gen 1 Audi TT was recalled to have rear spoiler retrofitted as the car generated sever lift at high speeds, resulting in numerous crashes on the highways. More about it here...

 

[goldmax]

Six people died in those crashes in Europe

 

[goldmax]

I would like to fit a wing if it makes my car more stable at high speeds, up to 100mph it feels fine but over this speed I really lose confidence as it starts to feel light and I'm worried what might happens next, very small feeling of left to right sway. I always end up easing off and coasting back down to 80 or 90 where she feels safe. Heavy powerful front engine cars probably don't experience this, I know it's to do with lightweight and mid engine but if a tail could anchor the car down a bit and keep it stable that would be great. I have Jamie's blocks fast road fitted to help.

 

[Alfanut]

I would like to fit a wing if it makes my car more stable at high speeds, up to 100mph it feels fine but over this speed I really lose confidence as it starts to feel light and I'm worried what might happens next, very small feeling of left to right sway. I always end up easing off and coasting back down to 80 or 90 where she feels safe. Heavy powerful front engine cars probably don't experience this, I know it's to do with lightweight and mid engine but if a tail could anchor the car down a bit and keep it stable that would be great. I have Jamie's blocks fast road fitted to help.

In that respect I feel Cipsonys’ side diffusers seem to make a difference. No need to ask how I know. At speed you can feel the rear plant itself more securely. No measurements apart from those that Cipsony made but my arse felt more confident at speed with them.

 

[goldmax]

In that respect I feel Cipsonys’ side diffusers seem to make a difference. No need to ask how I know. At speed you can feel the rear plant itself more securely. No measurements apart from those that Cipsony made but my arse felt more confident.

I'll have a look at those, are they easy to fit? Also ground clearance ?

I wonder how the car would feel with a proper wing and Cipsonys side skirts combined?

 

[Alfanut]

I'll have a look at those, are they easy to fit? Also ground clearance ?

I wonder how the car would feel with a proper wing and Cipsonys side skirts combined?

I’m talking about the diffusers, not the side skirts. I’ve bought those as well but haven’t fitted them yet. I’m yet to purchase the coil overs as I predict the lean with the standard suspension on sticky Hankooks will probably be an issue. I’m getting the occasional scrape of the fins over dips and bumps at speed which is annoying. In normal daily driving they don’t scrape but clearance adjacent to the tyres is reduced (just over 2”). I’m thinking something up front would be beneficial too but I’ve not found anything absolutely to my liking but I have ideas. Again, Cipsony has come closest.

That being said, having tasted @alfa1105s’ 4C a couple of weeks ago, his combination of wheels, tyres, springs, front splitter and rear wing felt very secure.

GMS I think has done a great job with his wing to eliminate as much drag with his wing as possible while adding downforce. For those who spend a lot of time at the track it is surely part of the answer.

 

[4Canada]

160km/h, CFD analyze provided by the wing supplier. It's an UK based company that supplies wings for Ultima GTR and Lotus cars so I tend to trust them.

160km/h is somewhat average track speed for street cars so hence we used that one. On our track average speed is 158km/h with our 4C.

You can make out further rough estimations of relation between fownforce/speed according to this:

View attachment 124121
..

Yeah, generic downforce / drag vs speed is pretty .... generic.

TBH, the two tracks that I most likely to be see on are perhaps too slow for real downforce to be effective. On my home track, I have an average speed of about 105 and a fast sweeper where I can feel that rear traction is the limiting factor - mid 90’s through there is the best that I can do, with sphincter fully puckered. Obviously, I have a lot of things that I could (and should) adjust before going to aero (not the least of which would be suspension so that I could fit wider tires, then the wheels to accommodate those). But regardless of tires, aero will always improve this corner. Not sure how much the other corners on that track will benefit though (mostly too slow, I fear).

The reason that I asked about the speed, and charts for different speeds, is that both lift and drag are quite geometry-specific, with drag varying by the square of change in velocity. Whereas a high aspect ratio wing will have a better lift to drag ratio at lower speeds, a lower aspect ratio (even at a higher angle of incidence) will still outperform it at higher speed). And of course, the wing in isolation is only part of the story - it’s interaction with the airflow around the car will limit what it can really do (although we’ll leave those kinds of calculations for F1 teams for the most part ). Although the discussion is far above my abilities in driving or physics, I would think that understanding the details would be critical to wing selection and adjustment.

 

[GMS]

I agree. We chose the most effective (large but low drag drag profile) single element wing that we could fit within 4C's dimensions. The CFD analyze for the wing is done in free flow, so yes the numbers are probably a bit off, but it's out of our budget range to afford wind tunnel and 4C has other critical aero issues to sort out priority (front radiator air stream flowing under the car).

It's step by step improvement, even though small. First we reduced the rear end weight by GMS carbon rear hood to decrease oversteer tendency, lower the CG and provide supprot for the wing. Then we added the louver, to decrease the aero lift (with closed rear glass, the airstream going down the roof towards the end of the car is trying to lift the hood, but with open slots in the louver, it can't so, the lift is decreased and the hot air is sucked out of the engine bay instead). Third step was the rear wing which is the major element to the rear downforce. And we need to remember, that it's the fast corners that big improvements in lap times can be made, not the slow, especially if you're low on power, like the 4C is compared to other big guns. Accelerating out of a tight corner from 45km/h, instead of 50km/h is not much of a game changer in terms of lap times. Bringing 175km/h out of the corner to the main straight, instead of 170km/h it is. And if we take a look at the CFD downforce/drag charts, the drag bhp consumption is not nearly as bad as the downforce is increased. Roughly we sacrifice only about 3% of bhp, while downforce is generated in amount of about 17% of the rear end car's weight (600kg rear axle weight vs. 100kg of downforce). That's decent. For me, it's a fair deal, I'll take it. So far, we've shaved 2.5s off our lap times from 1.38.8xx to 1.36.3xx with increased aero, and no change in power, yet I believe we can take another 0.5s off, with fine tuning the rear wing's AOT in combination with suspension fine tuning. So the rear wing helps us a lot, as the car finally feels more stable at high speed sweepers, but surely, entire car could be even further optimized by the use of wind tunnel etc., but that just ain't happening. We must stick with methods that are economically viable for us. For me, if the lap time will drop next time after next mod, the job is done. And that will be the front hood with reversed airflow (above the car, instead under the car).

 

[LP560-4C]

Yeah, generic downforce / drag vs speed is pretty .... generic.
Obviously, I have a lot of things that I could (and should) adjust before going to aero (not the least of which would be suspension so that I could fit wider tires, then the wheels to accommodate those). But regardless of tires, aero will always improve this corner. Not sure how much the other corners on that

What tire size you run that you may need wider ? go more than 275 ? just curious

 

[LP560-4C]

seeing if this link works w/ a tire size comparison 235/35/19 vs. 275/35/18 are as close as you can get w/o much impact on the speedo..........

Tire Size Comparison

Tire size comparison the easy way. Use our tire size comparison calculator to compare diameter, width, sidewall, circumference and revolutions per mile.

tiresize.com

 

[4Canada]

What tire size you run that you may need wider ? go more than 275 ? just curious

Rear 245, but with stock (not track) shocks, despite the beefed up roll bars, she corners like a torpedoed battleship. Anything wider (would like to go at least 255) will rub the bodywork. Also, 215 fronts with such wide rears would probably not be ideal, but I would have the same problem there.

In any event, the suspension would have to be well sorted before adding significant aero anyhow.

I’m keen to see what Rudi comes up with for the front end. Certainly, reversing the radiator exhaust (to come out the hood) will help and ads front downforce with really no drag penalty, but I’d be surprised if that is sufficient to balance such a monster wing. Again, a stiffly sprung car must help here.