GT wing - track use (SMP + WP)

[The Green Goblin]

Hey Guys,

I'm considering purchasing a proper GT wing (maybe voltex or arrive devil), the primary reason is to have more stability & traction at the rear for high speed corners/bends & the ability to take these corners faster. I find currently the ass slips out a little too easy when car is being pushed. Car is an NB8C.. proper suspension & sway bar set up running Rs3's etc.

from the very little i've read here is what i can expect;
- increased down force in corners
- increased drag on straights (may result in slower top speed)
- saving in time of upto 1.5 secs
- ive seen mx5's + S2000 owner comparisons & it seems pretty legit

from the online vids i've seen, some have reported nil drop off in straight line speed but improved corner entry & less traction loss, which is ideal. Hoping to get some more input from those who have done this mod, the results from it & what set up you have, primarily with the SMP GP circuit & WP tracks in mind - would this mod make a considerable difference & is it worth pursuing?

cheers,
Jas.

[The Green Goblin]

***Moderators - my bad - i think this may need to move the non state specific motorsport section, please move if so.

[greenMachine]

I am not sure what a 'proper GT wing' may be, but any wing will probably improve DF at the rear. The question is really more nuanced than getting a 'proper', or even 'the best', wing.

If you are going to play with aero, it needs to remain a balanced car (assuming it started that way). That means determining what is the end of the car that is hardest to get DF out of, and that is pretty much always the front. The next question is what aero/bodywork mods are permitted under your current (and future) rule set, and especially how extreme can you go at the front. That then points at what you might look at for the rear.

Just adding a wing to the rear is a recipe for high-speed understeer, not what you want at T1 at SMP or PI. If the car is unbalanced, that should be sorted first unless the imbalance is aero related (eg the rear end lift that MX5s experience at high speed).

Look at some of Lightyear's work on here, he has done a lot of work on aero and you can learn a lot from reading his posts.

A wing will always produce drag, and it will be proportional to DF, and it and DF will rise at the square(?) of airspeed over the wing. So lap time will be a tradeoff between top speed and corner speed. So on a slow circuit you might run lots of DF (and drag) for better corner speed, but on a high speed circuit you might try to reduce drag (and increase top speed) by reducing DF - lots of experimentation needed to optimise these settings for a particular car at a particular circuit so that the fastest laptime is achieved. This also highlights the importance of efficiency of the wing (L/D ratio), and things like endplate design and gurneys.

The 3D wings are pretty draggy compared to 2D wings. A 2D wing will be more efficient, and the higher it is mounted, and the further back, the more effective it will be. This is probably the most extreme example of a high mount 2D wing that is commercially available (that I know of).

A good wing will produce BIG loads on the mounts, especially if it is a turbo car doing 240+kph. How it is mounted to the car needs careful consideration. Same goes for the front aero.

Just some points to get you started thinking about the issues! I'd suggest you do some searching on here, there is quite a lot of info on this.

[Luke]

Sorry no feed back on the aero at SMSP.
I have dríven dríven 2 MX-5's with rear wings and front splitter setups at Wakefield Park, so no high speed stuff. Both were dedicated stripped out naturally aspirated revvy NB8A race cars.
To be honest I don't think the aero on either car made much difference at Wakefield Park other then turn 9 at full speed was a bit more comfortable than I am used to. Comparing them to my road going, non aero enhanced, heavy NB SE, nothing in it. All did 1'08's at Wakefield Park on Yokohama A050's. My SE speed wise at the end of the straights was in the middle of the 3 cars, which incidentally was also in the middle of the times as well. And nope my SE is not that powerful hence the middle of the pack top speeds. Just much more mid range torque and spring rates at about half that of the race cars. I make that point as I can ride the bumps and curves so much better.

But the real question I have to ask is why are you going down this path? I'm asking because of your tyre choice.
You are using what I assume is Hankook RS3's and you are looking at Aero. I thought proper R-specs would be the next progression, well before Aero.
And wouldn't you need to balance it with a front splitter or similar as well. Otherwise I gather it may become understeer city from what I've seen happen to some others that have gone and put a wing on the back.

What lap times are you currently doing around Wakefield Park and GP circuit and what speeds are you hitting before Turn 1?

[Magpie]

This will not be a short post...

This is from SMSP using data from WTAC, which in Kyle Forster used to design my new wing. This shows the difference (simulated) by changing drag/downforce etc without changing the cars power. The blue line is 8 secs (simulated) faster (1:36.19) with the orange doing a 1:41.15. Decreasing drag by 10% could achieve a lap time of 1:44.61 (brown), if I could drive it as per the simulation...



The orange is using full pro-am type aero and down the main straight you can see the impact that drag will have. However through the corners there is a gain and hence why faster, despite the sacrifice of straight line speed. This is the trade off you need to consider. However, to have high corner speeds requires tyres (and a suspension setup) capable of achieving them. A G Plot is very useful for this.

Hmmm by Eipeip, on Flickr

When considering a wing, not only do you need to consider the type (2D, 3D, twin element) but how this will impact the cars aero balance. A 3D wing works better at lower speeds and can be effective if it is not in clean air because of the 3D shape. Whereas a 2D or twin element needs clean air. The key is to keep the air attached as it comes down the rear window.



If the air does not stay attached to the rear window then it can not be fully utilised by the wing, you want 'clean' air at the wing not disrupted flow.

Another point to consider is how the data is portrayed by makers. For example with my wing the data is published as if the wing is in free air, that is not mounted. real world testing shows that the mounts have an impact on the airflow and hence the wing is not as efficient in real life as the published data.

This then goes to the argument of swan neck vs 'normal' mounts. Again a real life experience with a boot mounted mount was as the car went faster the boot was pushed down further (against the seals) hence the AOA was changing for the worse as downforce was reducing. Further it can deform the boot if you do not keep a close eye on it. The benefit of the swan neck is that air flow under the wing is not impacted, however requires extensive 'body' modifications to install and make effective.



By the way, my current wing (and mounts) could be available in July...

Saving weight will allow the car to accelerate faster where as drag will allow a faster speed. Downforce MUST come at the expense of drag, hence evaluating what you will benefit most from is critical.

With respect to drag, I would suggest you do coast down test to evaluate different setups. Suggestions to decrease drag:

1. Remove rear bumper/difusser and test if drag is reduced. If 'better' then cut bumper down (or remove completely). Then consider if a difusser can be designed to improve aero. With a dual element wing a difusser may not be required.
2. Use vortex generators on hardtop. Evaluation can be done with wool tuft testing.
3. Removing the air from inside the wheel arches. This can be evaluated by differential air pressure tests.
4. Making a front air dam and 'splitter'
5. Brake duct holes to inside the 'mouth'.
6. Mouth size could be reduced. Reducing the mouth size is easy to test (coast down). This should be done with caution as it will decrease air flow into the radiator.
7. Canards to improve from downforce, again this will be a major consideration if a dual element wing is used. Canards are more 'tweaking the balance.
8. Remove rear/front mud flaps

If you have data logging capabilities then you can use this to evaluate drag. A quick way to check how changes have impacted the ca is to compare acceleration, ACCEL = 'Accel G Force'*9.80665. This converts the Accel G Force into acceleration m/sec².

The picture below shows Sydney Motorsport park in 2017 (blue) was accelerating faster than red (2015) at the same speed.

ACCEL by Eipeip, on Flickr

Happy to provide some more feedback/real world tests. As others have said you need to decide what direction you are going and if you want to use your horsepower for straight line speed or to overcome drag and increase corner speed. Also, do not neglect your suspension as downforce will impact available travel on your dampers...
This is a good thread to read through https://www.miataturbo.net/race-prep-75/post-your-diy-aero-pics-63769/

[Tony]

Jas,

I agree with everyone above. Aero is a whole lot more than simply bolting on a wing. Aero balance and centre of pressure have been mentioned. Kyle's videos in the following link are a good place to get a whole range of info on aero (and on lots of other stuff too).

https://www.youtube.com/user/Kyleengineers/videos

I find currently the ass slips out a little too easy when car is being pushed. Car is an NB8C.. proper suspension & sway bar set up running Rs3's etc.

If properly set up the back of the car shouldn't move around too much. So, if it were me I'd get the suspension checked and set up by a professional shop that does chassis tuning, with a good alignment and a corner weight; and also take the next step to R-spec tyres.

[Magpie]

I find currently the ass slips out a little too easy when car is being pushed

Is this happening on corner entry, apex or exit?
Does it start out fine and then starts after a few laps?
Alignment?
Tyre pressure/temps?
Rake?

[madjak]

I found my home made wing made a massive difference on certain corners. I can carry far more speed through the long sweepers with the wing on vrs when it's removed. The car is far more settled and has a lot more traction.

I think the whole drag vs downforce issue is overstated on most Australian tracks if you are using any modern wing profile. The gain from corner exit speed well and truly negates the loss of speed down the straight. Maybe Bathurst is the only track in Australia where that rule doesn't necessarily apply. On an MX5 you do need to get the wing up into clean air unless you are running a lightyear fastback or something that flows the air better over the boot.

There is also a fallacy that you need power to compensate big aero. This is pretty much wrong. You can have a stock 1.6 NA kitted out with a front splitter, rear diffuser and big wing and it will lap faster with more aero than without on 98% of the track in Australia. The loss in acceleration (which occurs at high speeds) can never negate the corner exit speed gain on any track that I've seen (bar Bathurst).

Just make sure whatever you add is not crazy heavy, and is balanced front and back.

[Nuddy]

I find currently the ass slips out a little too easy when car is being pushed

Is this happening on corner entry, apex or exit?
Does it start out fine and then starts after a few laps?
Alignment?
Tyre pressure/temps?
Rake?

Seems to me that you need to get the handling sorted first, before ctomolicattivng the issue with aero.
Like Magpie says and in addition spring rates, damping, sway bar settings.
Once you have the handling sorted then move up to the best tyres you can afford before spending on aero that may or may not help.
The previous owner of my car recorded his best lap times without aero. I bought the car without the wing, which he sold separately.

[Tim_cyc03]

If you want a GT Wing, then buy a GT Wing. If you don't like it you can always take it off.

Having a quick look through your thread there are a lot of other ways you can gain some loss of lap times at the track, but sometimes you just need a bit of wing.

I have not used the Voltex or Arrive Devil wings, so the following comments are just from looking at pictures, but I would not recommend using them. However pretty sure Voltex have their own wind tunnel, so probably know what they are doing.

https://www.miataturbo.net/race-prep-75 ... ics-63769/

Study that thread if you haven't already, I'm sure you will find all the answers you need there somewhere in the 80 odd pages.

What class are you building for and what are you limitations?

The singular wing is the best of the lot IMO.

[The Green Goblin]

wow thanks all for the detailed comments..

having a read of these just shows how very little i know in this space & how complex an effective aero set up can be.. i.e. me thinking that its a simple case of slapping on a wing & read to rumble, not considering impact it would have with the front of the car.. turn in.. understeer etc. in addition my car's level of development is not yet at that stage.. it would need much testing, analysis & data logging which to be honest isn't my forte.

to clarify, this idea came about when chatting to a mate in his s2k.. he removed his voltex wing on a SMP day & said that there is noticable difference with respect to stability around longer bends & how fast he can enter a corner, he ran slower times without the wing, said it was of great help & that he can really feel the difference let alone see it in his times using or not using the wing however, he had no other aero on the car (no splitter, canards, diffuser etc). I didnt get to ask him if adding the wing changed the characteristics of the car.. there was another s2k at the track with the same spoiler who i matched in most corners quite well except turn 1 at SMP.. which he entered into much quicker, which when seeing both examples, it led me to beleive that all that's needed is the spoiler, again reading your posts ive realised it aint the case, the last thing i want is to change the handling characteristcs of the car & induce understeer..

about the car - full street trim, untouched engine besides full exhaust (racing beat manifold) BD roll bar, i have monotube tein dampers, set to a above medium (not full stiff) setting, front + rear sway bars with end links, agressive/track wheel allignment (set up by corse automotive who specialise in race car set ups), the car has been corner weighted & i was told that it's balanced quite well out of factory. Car sits fairly flat with minimal body roll around corners & other people who have dríven my car or sat passenger gave me their approval that it's a decent set up (friends, race instructors, mechanic etc.)

the only things i can think of & thanks to you fine gents for pointing out one of them which i totally did not even consider are:
1. use of R spec tyres (current are hankook Rs3's which are road legal - semi slick), i will look into this in near future
2. the car does have slight rake, in that iv'e used tein's recommendations when lowering the car.. the rear is slightly higher than the fronts (literally 1cm or so), would this have bearing with respect to weight shift - am i better off having leveled height front & rear?

the car slips in corner entry predominately.. i find hard braking/weight shift is the contributor of this, which is evident in the below vids:

WP:


SMP:


all other advice welcomed. i dont compete in any race series.. just me myself & I against the time.. for now.

cheers,
J.

[plohl]

What are you spring rates and sway bar thicknesses? Are the sway bars hollow?
If you don't know this info, what brand is everything. If you don't know the brand... figure it out. This is bread and butter information needed to set up the car.
Next, what are you alignment specs?

[Magpie]

When comparing with another car, were the tyres the same (heat, cycles, temps, pressures, size), weight, brakes, driver skill, etc etc etc. it is very difficult to make specific comparisons between different cars. What works for one does not mean it will work for you.

Adding aero is not as simple as just adding and forgetting, more times than most it makes you slower.

As I mentioned, set a baseline, add changes and test/evaluate.

Looking forward to reading your posts on how you progress.

[lightyear]

I am starting to make wings. If you want one you just need to specify the wing width and mounting width. It's an SM183, google it to find the info, it's the best go to wing profile to suit a wide range of cars. Also have the second element, but you won't need that unless you are going real fast.

[lightyear]

And if you run a real wing such as mine you will need a proper front splitter to balance it out.