MK5 Golf GTI
All Things Mk5 => Modifications & Technical Area => Performance Modifications => Topic started by: fuscobal on February 02, 2012, 03:26:28 pm
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Following Bruce's idea with the OEM parts, I thought we should also have a brother topic for aftermarket parts. If the aerodynamics of an OEM vehicle is more about improving mpgs, the goal of aftermarket parts is to bring more downforce while keeping the drag as low as possible. Generally there is a consensus regarding parts that should be added to a vehicle in order to increase downforce and thus cornering grip. The contenders are :
1) Front air-dam > can be part of the front bumper or an add on to the lower side of the bumper. This part alters the ratio between the high pressure slow moving air over the car and the low pressure fast moving air under the car. The lower a car it is, the more effective an air dam will be.
2) Front splitter > can be used with or without the air-dam to increase the downforce even more. It acts similar to the air dam by creating a high pressure area above it and low pressure area under it wich sucks the front of the car to the ground (see Bernoulli principle).
3) Front wing > this one's not practical for usual sedans but worth mentioning since it's highly effective on F1, Pike Peaks or similar other cars.
4) Front canards > these are small wings mounted on the sides of the front bumper in order to bring a little bit of downforce and help with the fine-tune of the front-to-rear downforce ratio. They can also produce vortices of low pressure air wich help to reduce drag.
5) Flat underbody > Flat panels installed to the underbody of a car cover the car's various mechanical parts and smoothen the air flow, keeping the low pressure and again sucking the car to the ground. They also help with the mpgs and reduce drag.
6) Rear diffuser > acts as a way of speeding up airflow (lowering pressure) and then slowing down airflow (increasing pressure), in an aid to create downforce and smooth out turbulent air exiting the rear of the car, matching the outside high pressure air while minimising drag.By providing what is essentially an expansion chamber at the diffuser's exit, the airflow has to flow and expand back to ambient pressure in the diffuser.
7) Side skirts > these make sure the low pressure air under the car moves to the rear only and doesn't interfere with the air outside the car.
8 ) Vortex generators > Vortex generators were firstly developed for the aircraft sector, this technology has made it's way into Motorsport and car design. The main function of this device is to delay air flow separation. Air flow separation is when the airflow of a object detaches from the surface and creates eddies and vortexes. This basically means that the car will result in more drag and will reduce top speed and potentially downforce due to the turbulent air entering other aerodynamic device ( rear wing for example) and the wake of air left behind the car.
So by positioning vortex generator over the rear of the roof, you effectively help to reduce drag and increase downforce via the rear wing. This will have the effect of reducing the overall drag created by the car travelling through the air at speed and the faster and faster you drive the more effect this device will have. Especially effective in speeds in excess of 60 mph (100 KMP) speed ranges.
9) Rear wing > this is essentially a reversed aircraft wing and acts to increase downforce while also increasing the drag. They usually have multiple mounting angles so that a good balance between downforce and top speed can be achieved.
This is only a short story of it but you can read more in detail articles :
http://www.rapid-racer.com/aerodynamic-upgrades.php
http://en.wikipedia.org/wiki/Bernoulli's_principle
http://en.wikipedia.org/wiki/Ground_effect_in_cars
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Now, starting from the list above, let's see what we can do on our Golfs to improve downforce for track days :
1) Front air-dam > there are many add-ons to the OEM front bumper but no downforce data available. Most are for cosmetics only, few have been developed on track but no data for these also. The answer I got from VwRacing for the only air-dam developed on track was a little dissapointing. They said they did not test the air-dam on a wind tunnel but their drivers said a difference can surely be felt on track with it on.
2) Front splitter > same as above, many carbon splitters to add under the bumper but too small to have a real effect on downforce
3) Front wing > I think we can skip this one.
4) Front canards > I think we can skip these too as they are not too aesthetical on our cars. No one makes them for us and the trouble of making custom ones would be too big for a small revenue.
5) Flat underbody > This has also been covered on Bruce's topic of improving aerodynamics with OEM parts. While the front of the car can be easily covered by the long tray, the rear is a little more difficult to to in one piece as there's no available part.
6) Rear diffuser > highly effective part if properly done. Can be seen OEM on several cars like EVO 10 or Clio RS but again is quite small to be very effective. A real diffuser goes very deep under the car and at an angle of 10-15deg to the ground. A real difficulty in making an effective diffuser would be avoiding the exhaust.
7) Side skirts > Many on the market but again no data
8 ) Vortex generators > Can also be seen on EVO 10 mounted as an OEM part but don't know how many would be willing to try them on their Golf. These would probably be quite easy to install (universal ones should be just good). Also, don't know how effective they could be on hatch-backs as they would be too close to a presumptive rear wing !
9) Rear wing > Although there are several world renowned rear wing manufacturers, no one makes a true wing for our Golfs but VwMotorsport wich again sells it through Bildon in US only (very weird decision of not making them available through an european dealer as it would be much cheaper for us this way)
PS : I bolded only the ones I considered useful for our cars
Waiting for your replies with thoughts, links of parts available for our cars and aerodynamic data that some of you may have !
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Thank you, interesting topic again !!
:happy2:
I' going to try providing some useful data and at least my opinion while you already have listed the main points.
First let's have a look at the aerodynamic lift we have on our cars at stock condition:
From German magazine 'SportAuto' Supertest Golf V GTI
Wind tunnel: aerodynamic balance
* A: 2.23 m²
* drag coifficient (cd): 0.33
* index (cd × A): 0.74 (more than Mercedes S-Class)
* front: 2 kg lift
* rear: 37 kg lift
@ 200 km/h (!!!)
Golf V GTI: lift 2 kg front and 37 kg rear
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328207486_3041.jpg&hash=0be0d093e33d201c80983b6abbaf29018277eec1)
Golf R32: lift 3 kg front and 36 kg rear
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328207787_3041.jpg&hash=93be28b012098d526cc61ca8e465636e6227a7e4)
Audi TT: 23 kg + 24 kg (wing position lifted)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328204924_3041.jpg&hash=47aa01efac494a925f985ad0a896eb87c55426eb)
Golf V: sadly no data
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328207959_3041.jpg&hash=174a49eae8830d46685898e1ff23809c9317084c)
Focus RS: currently no data - will add them later > 8 kg front downforce; 4 kg rear lift
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328207910_3041.jpg&hash=0a178dfa2914118199011dbdd9f9dca04ae6d5be)
So in the case of the Golf (like almost all hatches) rear lift is by far more an issue than front.
Even more it's interesting to know what parts of the car do cause what amount
of drag (and most likely lift):
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328210958_3041.jpg&hash=0976beb478334bdfe817587596809b420c1ea309)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211047_3041.jpg&hash=adafefa4b21b258555567e5087085d86e680ac59)
From reading books about aerodynamics I know underside and rear of the body are
most important. Rear roof + side spoilers (look at the Golf24) are the way to go.
But what are we able to achieve with a modded GTI?
The Scirocco R Cup has a downforce of 200 N (~ 20 kg) @ 200 km/h total both axles:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328210495_3041.jpg&hash=332b55f73f930668b0697ac10aefacf845bca123)
It's gonna be extremely difficult to get even more downforce than this kit car with
flat underside an rear wing.
So next question is what we have to do to reach this?
Without any doubt it's easiest not to make own developements but have a look at
Golf based race cars instead:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211129_3041.jpg&hash=9f69fcce778b9039c6da83fabe11add9807cd524)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211186_3041.jpg&hash=3b4d7eeed3551d3dcfd8a5bb0097d5b58c2017af)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211358_3041.jpg&hash=4d4001da41ffa64426bb76ce380481f812a50ca7)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211730_3041.jpg&hash=d6b528cb321b8444255eb62a4fb111e62c28f5f1)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211815_3041.jpg&hash=de77296586190e568b4963f1bb8cf631c9465c42)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211942_3041.jpg&hash=5dda7a47d74aa7ade575f393a2f31e434f265b36)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211420_3041.jpg&hash=79e98d4abc931d2a60ce6f848265089a247e8c66)
(of course no rear muffler fitted, but have a look for the Mk.VI Milltek which is extremely sleek)
Some high performance street cars:
997 GT3 RS:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328212138_3041.jpg&hash=993c6b1bb0d10fb0b0183735046b6669085e8516)
Panamera:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328212230_3041.jpg&hash=f0907767d6b1840cc174714ad66e0a8c0947b00b)
Ferrari F355:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328212267_3041.jpg&hash=70c6ff56bdb6dc2572e87bcf73e5fc36a4e61f2a)
Nissan GT-R:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328212457_3041.jpg&hash=b5ad951b8be69af550c0e4c908903d64b512c40f)
Mercedes SLR:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328212726_3041.jpg&hash=7fcf628ea2a62908922d25c1afd95e2faebd4a40)
All of these have a flatter underside compared to a Golf. Some have a diffuser that
may work. But don't get confused: these cars do not have real downforce. They just
have less lift !!
1) Front air-dam:
Fuscobal, Im with you. I think the VWR is the most efficient. The Rieger looks the same
in shape. I run the Volkswagen/Votex which seems a more elegant alternative to me.
2) Front splitter:
Kerscher make one:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328213544_3041.jpg&hash=d908d05123200960787b56ed435cb6f891271c94)
Of course before purchasing one (or making one on your own) I'd think about the
question if you really need one.
Another idea is to make a splitter as part of a complete underbody tray including a
rear diffuser.
6) Rear diffuser:
To me the Clio RS diffusor seems to have a proper shape:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328214145_3041.jpg&hash=d693949bb488ea59f4e09f8989c09fb7dc5aca70)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328214393_3041.jpg&hash=16be53a97859fe10e318d4c24a6f210a7fc58a14)
9) Rear wing:
If you don't want to fit a huge wing some roof spoilers may be a less efficient but
more elegant alternative:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328212927_3041.jpg&hash=d230c62705d9e7f6f0a67e6e09ba2a43dc682c4c)
> www.vary.co.jp
There's so much I like to say/write about it, but that's it for now. ;)
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the clio 197 diffuser definitely reduces lift. i think it ads 20kg of downforce or something.
when i head my clio it would suck leaves etc up off the road and stick to the underside and back of the car so I'm sure it was working.
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these reckon 70kg of downforce! doubt that but I'm sure it was 20-40kg or something
http://www.autoexpress.co.uk/carreviews/firstdrives/68538/renaultsport_clio_197.html
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Thanks for this link. :happy2:
Bespoke body panels add a sporting, muscular image to rival the Clio V6 - especially from the rear, where it has a huge aerodynamic diffuser under the bumper. Those custom panels are bigger than on the standard version, too - although they need to be to house the 10mm longer wheelbase and 5cm increased track of the 197.
The changes aren't only for visual impact. That diffuser really works, and can add up to 70kg of downforce.
Well, they speak about "up to 70 kg", so it seems this is at top speed (or downhill).
Next question is it the rear axle downforce value (which I don't believe) or just the
amount which the diffuser adds to whole aerodynamics. So there may be some lift
at the rear roof (as always on a hatch) and up to 70 kg downforce at the diffusor
which may give a total near zero lift.
A by far better value than on a Golf of course. :wink:
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its definitely better. the RS 197/200 is a seriously good handling car and the brakes actually give some confidence, unlike the golfs! :sick:
the amount of debris you get under the car is crazy on the 197/200 though. i had to remove mine a few times to clean all the wildlife out from it!
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Wow, very good info Bruce. It's for the first time I see the downforce numbers for the Golf GTI. The 2kg of lift on front could probably be negated by the VwRacing air-dam (wich I've already ordered by the way) and maybe even have a little downforce. Does anyone have an idea of how much downforce can an air-dam bring to a street car ? (I know it may vary a lot from car to car but a medium value would give us an idea). s for the 37Kg on the rear, we probably need a large wing to negate that and add downforce. I tried contacting VwMotorsport and Becker Carbon but no answer so I would look into Simon McBeath wings (made by Reverie & DJ Racecars). Some links for these :
1) http://www.djracecars.com/carbon-fibre-wings-and-aerofoils.asp > 100mph, 1400mm span wing downforce data > http://www.sm-designs.ndo.co.uk/images/singleDfvalpha.gif
2) http://www.reverie.ltd.uk/225mm_chord_wingdata.php > very nice data of downforce vs drag vs BHP absorbed vs angle of attack vs span ...
3) http://www.sm-designs.ndo.co.uk/ > Simon's website from UK > This guy seems to have a huge background in wing design. Look at the cars he did until now !!!
PS : The downforce of the Scirocco Cup can be without doubt bettered because those cars are limited by their category. The wing cannot be installed higher than the roof of the car or further back than the rear bumper wich limits its effectiveness. They may also have a limited span. I would do a wing wich looks more like this one >
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.autoblog.nl%2Fgallery%2FVolkswagen%2FScirocco_R24%2FVW_Scirocco_R24_10.jpg&hash=32f9e5f569c59867c61c8657b5a997a7c73fca6d)
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I quite like the look of the gurney strip for the spoiler. Wonder is any European manufacturers make one?
http://www.vary.co.jp/reife.html
I like th look of this too but don't know what the quality would be like and if it would actually make a difference
http://www.ebay.co.uk/itm/110717469037?redirect=mobile&autoredirect=off
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Fuscobal,
You know I had 5 kg + 35 kg in my mind, but compared to 1.4 to of a complete Golf it's almost the same.
Many people tell about the rear feeling light at high speeds. When braking it is light on rear !! :grin:
I strongly believe I already have (very small) downforce on front with my Votex + undertray + lowering.
I guess the VWR should give you ~ 5 kg. You are already lowered as well, so you'll have some downforce then.
Yes, the Scirocco R Cup uses the OE Votex rear wing which has to be mounted in a TÜV conform position.
It does not givve the amount of downforce on these cars possible with a higher position and steeper angle.
Keep in mind a diffuser is more efficient than a wing. A well designed diffuser provides both downforce +
reduction of drag at the same time. Any wing will allways produce some drag as well.
But there's also a good point on this: drag produced on top of the car will lift the front (by a small amount).
So not only the wing's downforce, but even it's drag will optimize front/rear balance.
If you like to mod your exhaust (eliminate rear exhaust for example) I'd consider a diffuser as well. The Clio
RS diffuser seems even small enough to combine it with the Milltek Mk.VI exhaust:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328224591_3041.jpg&hash=e0cbcb77f1712564e5d690bfae38a0ba17532fb5)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328224652_3041.jpg&hash=3badc9db69fef00570d1a0092af6473069f9839f)
If you watch the GTI24 pics carefully you will recognize the small 'spoilers' on the sides
of the rear window:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328225047_3041.jpg&hash=52bfae7f878e45f34db8fcd5ebb168e095f8c569)
All Sciroccos come with it from factory:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328225457_3041.jpg&hash=686c1df6d30607c7f3ec7e111c5e69171a4dbd21)
and even many other cars:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328225166_3041.jpg&hash=5cc14d79060c2336968e5f83ff57d26cc6c67660)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328225087_3041.jpg&hash=f561f1b458d96f3f1f4586ca10842ebc72631781)
Renault Scenic and many more as well . . .
Why not the Golf?
ps:
I was looking for a roof spoiler similar to the Vary/Reife, but never could find one.
If you have a Mk.VI be happy to have a much more efficient rear roof spoiler from
factory than the M.V came with.
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My trouble with the big rear wing would be how to fix it to the roof of my car. The one seen on the Scirocco 24 pic posted by me seems to be fixed only by some adhesive (I can't see no screw/bolt there). If I have the wing, I think I can replicate those black aluminium pieces (I will have to cut a cardboard on my car's OEM wing and use it as a mold for the aluminium part (the OEM wing does not have perfectly straigh shapes so I will have to take the mold on the cardboard first and then make the aluminium part after the cardboard). There are 2 question here :
1) Will it be enough for me to use an adhesive to hold the wing into place (50-70Kg of downforce is quite some weight). The 2 aluminium pieces catch on the OEM wing like a claw (from under and above) but the cantact area is really thin (like 5mm or whatever the width of the aluminium board used is) !
2) Supposing I find a strong enough adhesive, will the OEM wing hold the big rear wing + 50-70kg or will it break > I don't know if the metal boot lid has a reinforcement that goes inside the OEm wing as well or the OEM wing is a simple plastic add on to the metal boot lid with no metal reinforcement !
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Ford Focus RS:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimg3.sportauto-online.de%2FFord-Focus-RS-fotoshowImage-f95bf2fd-255720.jpg&hash=b19ac153c46f253acaa7c159daf2dd742c490c76)
Fahrzeugstirnfläche (A): 2.350 m²
Luftwiderstandsbeiwert (cw): 0.36
Luftwiderstandsindex (cw × A): 0.86
Vorderachse: 8 kg Abtrieb (front downforce); Hinterachse: 4 kg Auftrieb (rear lift)
Ford Focus RS Raeder Motorsport:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimg2.sportauto-online.de%2FRaeder-Ford-Focus-RS-Aerodynamik-Windkanal-fotoshowImage-58ba5851-449517.jpg&hash=a1139cbca8f663e74b345f991460936495778bdb)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimg2.sportauto-online.de%2FRaeder-Ford-Focus-RS-Aerodynamik-Windkanal-fotoshowImage-a9f95302-512955.jpg&hash=f5ce61306cb7129722ad9fc687b2325d3ee93211)
Fahrzeugstirnfläche (A): 2.350 m²
Luftwiderstandsbeiwert (cw): 0.35
Luftwiderstandsindex (cw × A): 0.82
Vorderachse: 0 kg Abtrieb (front zero lift/DF); Hinterachse: 9 kg Auftrieb (rear lift)
Während der Serien-Ford Focus RS im Windkanal an der Vorderachse mit leichtem Abtrieb (rund 80 Newton) gemessen wurde, zeigt die Raeder-Variante bei der Messung an gleicher Stelle eine neutrale Null. Eine etwas stärkere Auftriebstendenz offenbart sich auch an der Hinterachse, die bei 200 km/h nunmehr um 85 Newton (Serie: 40 Newton) entlastet wird. Der tiefere Grund für die geringfügige, gleichwohl ohne Konsequenz bleibende Verschlechterung dürfte in der Tieferlegung zu suchen sein. Trotz der breiteren Bereifung fällt der cW-Wert mit 0,347 (Serie: 0,36) tendenziell aber etwas besser aus.
http://www.sportauto-online.de/supertest/raeder-ford-focus-rs-im-supertest-fronttriebler-wird-zum-porsche-schreck-3383831.html?show=2
Golf Mk.VI GTI Edition 35:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimg4.sportauto-online.de%2FVW-Golf-GTI-Edition-35-Windkanal-fotoshowImage-70c3f98f-526848.jpg&hash=fdb879afa0a364f23720f6fa388626f30c1b8dc8)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimg2.sportauto-online.de%2FVW-Golf-GTI-Edition-35-Windkanal-fotoshowImage-5b8ed7af-526847.jpg&hash=5c88f2f3f76c27406d02b1917e45672e4e68488c)
Fahrzeugstirnfläche (A): 2.230 m²
Luftwiderstandsbeiwert (cw): 0.31
Luftwiderstandsindex (cw × A): 0.69
Vorderachse: 0 kg Auf-/Abtrieb (front zero lift), Hinterachse: 31 kg Auftrieb (rear lift)
In aerodynamischer Hinsicht hat sich in der nunmehr sechsten VW Golf GTI-Generation einiges getan. Obwohl der cW-Wert signifikant verringert werden konnte, und zwar von vormals 0,33 auf jetzt 0,31, sind auch die Auftriebswerte verringert. Die statisch mit 882 Kilogramm belastete Vorderachse bleibt bei 200 km/h unberührt, das heißt der Auftrieb liegt bei null.
Der cW-Wert hat sich signifikant verringert (von 0,33 auf 0,31) und der Auftrieb erfährt eine Verbesserung: Bei 200 km/h geht er gegen Null.
Golf Mk.VI R:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimg4.sportauto-online.de%2FVW-Golf-R-fotoshowImage-75ffd0c3-420732.jpg&hash=d71250e90a712beee0a1f98cf1e48f798bdd862f)
Fahrzeugstirnfläche (A): 2.250 m²
Luftwiderstandsbeiwert (cw): 0.33
Luftwiderstandsindex (cw × A): 0.75
Vorderachse: 5 kg Auftrieb (front lift), Hinterachse: 33 kg Auftrieb (rear lift)
Der cW-Wert fällt mit 0,33 nicht so windschlüpfig aus wie erwartet. Das lässt sich aber sowohl mit der großen Stirnfläche von 2,25 m² als auch mit den großen Kühlluftöffnungen in der Front und den breiten Reifen leicht erklären. Während der Auftrieb an der Vorderachse mit 47 Newton vernachlässigbar gering ist, steigt er an der Hinterachse bis 200 km/h auf 326 Newton an, was einer Entlastung von etwa 33 Kilogramm entspricht.
Audi RS3:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimg1.sportauto-online.de%2FAudi-RS-3-Sportback-Seitenansicht-Windkanal-fotoshowImage-d316fce0-498406.jpg&hash=e533bb20382d0e270e7f072563bf9b30be9df012)
Fahrzeugstirnfläche (A): 2.180 m²
Luftwiderstandsbeiwert (cw): 0.36
Luftwiderstandsindex (cw × A): 0.78
Vorderachse: 21 kg Auftrieb (front lift), Hinterachse: 1 kg Abtrieb (rear very slight DF)
Aus der Stirnfläche von 2,184 m² und dem cW-Wert von 0,355 errechnet sich ein Luftwiderstandsindex von eher mäßigen 0,78. Die ungleichmäßige Gewichtsbalance von 60 zu 40 Prozent (Vorder-/Hinterachse) wird durch die aerodynamische Konstellation etwas gemildert. Der Auftrieb an der Vorderachse beträgt bei 200 km/h 203 Newton. Die Hinterachse wird mit Abtrieb bedacht - auch wenn es nur vernachlässigbare 14 Newton sind.
-
Weird...why does the Raeder Motorsport Focus (wich is has lower ground clearance) has more lift than the stock car ? Shouldn't be exactly the opposite ?
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Yes, and it is loosing downforce on both ends :confused:.
-
It has 265 mm wide tyrers (at least 275 mm in real). Wide tyrers disturb aerodnamics.
Pardon me for the German passages. it's the genuine SportAuto text.
Reifenmarke: Dunlop Direzza 03G
Reifen: 265/35 ZR 18
Felgengröße (vorn): 9,5 J x 18
1.4 g instead of 1.2 g stock. :wink:
-
interesting to see the audi control arm covers appearing on one of those race cars!
-
Right. I know the owner and driver of this car and I may have inspired him
with talking about this topic for some years. At least I hope so. This Golf
is one of the fastest Golf TDIs ever on the Nordschleife. From origin it has
been a Golf TDI Cup car before (which Volkswagen did in Poland).
ps:
of course the lower arms change position when the car stands on it's wheels :wink:
-
Hmm, knowing the front wheels seem to bring a lot of drag and lift, maybe a well designed air-dam/splitter can also deflect the air around the wheels. As I can see from your graphs Bruce, if you find a way to deflect air around the front wheel you can have a huge benefit in both drag and downforce !
-
Just buy a pair of the small spoilers that are in front of the rear wheels and fit them
in front of the front wheels. I would not fit bigger ones as this may weaken brake
ventilation (unless you have some ventilation hoses).
-
From what I've read you need to avoid to big a dam in front of front wheels if you have a large overhang in front of it as you can add a significant front lift, so if you fit them as far forward as possible or limit the size.
You could fit two smaller ones like on the front of the new mondeo or focus.
-
Yes, such wheel spoilers can cause lift as the are fitt closely to the wheel (while still reducing drag).
You can just fit some cheap plastic profiles to the frontal edge of the front lip but these parts do
live quite dangerous on a daily driver. And keep in mind front lift isn't any issue on a GTI.
-
Info about the VwRacing air-dam added to my topic here > http://www.mk5golfgti.co.uk/forum/index.php/topic,12484.msg492709.html#msg492709
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A good airdam IMO is the one from Opel/Vauxhall Corsa OPC Nurburgring Edition
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi818.photobucket.com%2Falbums%2Fzz106%2Fstefandragnea%2Fopc.jpg&hash=433b6b1cd80d942526053126446bc1e5bbb4ed28)
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that looks similar to the maxton design one for the mk6 gti
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Elise and Exige owner's life is somewhat easier:
https://www.eliseparts.com/products/show/13/44/exigemotorsport-diffuser/
https://www.eliseparts.com/products/show/13/86/motorsports-rear-spoiler/
Same wing on ebay: http://www.ebay.de/itm/270914104756?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1558.l2649
Might be worth considering for the GTI as well. :wink:
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Don't worry bruce, we'll get there even if it's harder :smiley:.
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Actually Bruce's adice is very good. I'm thinking that wing is very similar to the Reverie ones but much lower price. If we can find one over ebay that has not been damaged, it may be the way to go ! Who cares it's a Lotus wing ?...it looks just like the Reverie straight ones but it's even larger 250 x 1500 vs the 225 x 1400 that I wanted to buy from Reverie !
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2) http://www.reverie.ltd.uk/225mm_chord_wingdata.php > very nice data of downforce vs drag vs BHP absorbed vs angle of attack vs span ...
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.autoblog.nl%2Fgallery%2FVolkswagen%2FScirocco_R24%2FVW_Scirocco_R24_10.jpg&hash=32f9e5f569c59867c61c8657b5a997a7c73fca6d)
Well guys, after searching for solutions for the rear spoiler both fuscobal and myself are seriously considering buying a Reverie wing and manufacturing the mounts(supports) for the wing.
Now, the issue is that these mounts have no obvious fixing points.
I am thinking of using the OEM trunk hinges.
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi1237.photobucket.com%2Falbums%2Fff469%2Fvladpanut%2Fsite_P2187589.jpg&hash=2042b923cbc07b7431efa5adea79149c32b55105)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi1237.photobucket.com%2Falbums%2Fff469%2Fvladpanut%2Fsite_P2187590.jpg&hash=458d918bc4bfe92487c1671e816813905a87f620)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fi1237.photobucket.com%2Falbums%2Fff469%2Fvladpanut%2Fsite_P2187588.jpg&hash=594923fcddaae6affb0469956bb7672e1924a1a6)
As you can see, if I am to use the OEM hinges I would have to cut through the rear spoiler (through 2 metal sheets).
My questions are:
1. do you guys have any other ideas for mounting the rear wing? Do you know how other Mk5 enthusiasts mounted their wings?
2. is it possible to cut the brake light cable when drilling the spoiler? Do you know where the line go through?
Cheers!
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Impressive ambitions !! :drinking:
Just two ideas:
- glueing alloy brackets to the rear window that distribute pressure sufficiently
- purchase used rear lid, weld a bracket to it and change lid before trackdays
It even wouldn't need any wiper w/ motor, inner panel etc. . . . :wink:
-
Thanks Holger!
- the gluing part is a good idea. From the prohots the Scirocco seems to do that also. I guess we'll when we design the mounts.
- I also thought about buying a used rear lid but I think it makes everything more complicated... I might go this path if I find a trunk lid with Privacy Glass and at a reasonable price. But I might be using this on winter/summer bases, not installing it before every track day.
:drinking:
-
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimg2.sportauto-online.de%2FBMW-M3-04-fotoshowImage-91b73221-219515.jpg&hash=3803f3aa46654a379702c3f42205038213dbc615)
Windkanal: Aerodynamische Balance
8 von 10 Punkten
Fahrzeugstirnfläche (A): 2.170 m²
Luftwiderstandsbeiwert (cw): 0.33
Luftwiderstandsindex (cw × A): 0.71
Vorderachse: 10 kg Auftrieb Hinterachse: 23 kg Auftrieb
Der mit auffälligem Powerdome auf der Motorhaube sowie angemessen ausgestellten Kotflügeln auf sich aufmerksam machende M3 tritt mit etwa demselben cw-Wert an wie die bisher sportlichste M3-Variante, der CSL. Die Hilfsmittel zur Reduzierung des Auftriebs bei hohen Geschwindigkeiten sind dafür etwas dezenter ausgefallen. Der auf der Kante des Kofferraumdeckels platzierte Gurney hilft, die ungewollte Wirkung des Fahrtwinds auf ein vernünftiges Maß zu reduzieren. Das Heck wird bei 200 km/h um lediglich 227 Newton entlastet. An der Vorderachse wurde ein noch geringerer Auftrieb, nämlich nur 102 Newton, registriert.
cd: 0.33
cd x A: 0.71
lift:
front: 10 kg
rear: 23 kg
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Interesting to see how much lift can even super spot cars have. This is probably due to the fact that they want to keep the ground clearance as decent as possible for street use. Also, by protruding with an air-dam or splitter further away to the front wheels you have a bigger chance of hitting on a ramp !
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i read somewhere that the PQ34 cars had problems with drag due to air collecting in their engine bays. the TTs however had vented wheel arch liners to vent this air and improve the drag.
is this something that the PQ35 chassis cars are also afflicted with? OSIR do vented wings for the A3 8P that i've considered purchasing when i next go over to the USA but i'm wondering if it's actually worth the trouble/expense?
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Great read:
http://www.google.de/imgres?q=OEM+Underbody+Aero&hl=de&client=firefox-a&sa=X&rls=org.mozilla:de:official&biw=1366&bih=637&tbm=isch&prmd=imvnsfd&tbnid=fwiOnIhJWk8ikM:&imgrefurl=http://www.rx7club.com/showthread.php%3Ft%3D873466&docid=kL9oEOrXUkJBOM&imgurl=http://www.madpsi.net/Aero-kits/MadPSI/Rear%252520Diffuser/Madpsi%252520-%252520F430%252520Underbody.jpg&w=640&h=395&ei=15KcT4StN4fEsgaM-tlK&zoom=1&iact=rc&dur=441&sig=106977374515276114731&page=4&tbnh=112&tbnw=181&start=66&ndsp=24&ved=1t:429,r:18,s:66,i:255&tx=82&ty=43
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Good read indeed. For our Golfs there aren't any options for a full underbody. Just took a look under the car several days ago and the cat + horisontal exhaust pipe are lower than the 2 horisontal flat sides so in order to install a full underbody wich can probably be made quite easy from flat panels, you have to lower the entire underbody by about 3cm. Then, for the rear diffuser, the rear muffler (resonator) stands in the way and is lower than the rear bumper (in my case at least). I've looked there and there is no space to move it upper so it has to be much flatter than already is to allow a diffuser to go under it. A better option is to simply remove it and stay with only the pipe but the noise will probably be too much for me !
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Fuscobal... I looked at the under carriage. If we just give up the rear muffler and possibly install another muffler in the center of the car we might just install a diffuser and not make so much noise...
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I think you can manage a couple of panels on the rear to cover the areas by the fuel filter and the first muffler for a start by using aluminium panels that aren't heat dependant you could improve the flow and another sheet could extend from this out between the rear suspension arms over the exhaust, it doesn't have to function as a diffuser it just has to smooth the flow to reduce the rear lift
If you can also create an amount of expansion by creating an angle to expand the air flow to reduce drag all the better and add some small ridges to control the lateral movement of the air then that is all the better I think it isn't that difficult rear fixing could also be metal strap fixed to the exhaust rear muffler.
-
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211420_3041.jpg&hash=79e98d4abc931d2a60ce6f848265089a247e8c66)
Guys.. why is the exhaust so long? Is there any reason why it shouldn't stop where the diffuser begins?
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Yes. Otherwise it would burn the diffusor.
There also may be some reasons dependent on the rules (RCN).
-
Bruce your friends car in the picture does it have the standard fuel tank or a race version, just wondering if he has fitted that panel flush under the fuel tank.
You don't have more pictures of the whole underside?
-
ATL Fuel Cell - keep in mind it's a diesel.
http://www.erft-racing.de/fahrzeug.php
http://www.erft-racing.de/galerie_bilder.php
Unfortunately I couln't fid any additonal pics that show the underside, but I guess the above pic
shows most you need to know.
:drinking:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fhighspeedfotos.de%2FCoppermine%2Falbums%2F242009Corso%2F24h2009RCN109.jpg&hash=1bc51292f424512bb84ef049597c23ab8cb07399)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Flh5.ggpht.com%2F_i1GUNpeTgoc%2FSmQR-fJfEtI%2FAAAAAAAAa0I%2Fs4HIsQAKB14%2Fs720%2FIMG_3213.jpg&hash=26390a7ebefac4d7ef10404bf9c6462c37d3b3d9)
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Looks like serious downforce: :smiley:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fk59%2Fdawnskaybug%2FIMG_0198.jpg&hash=76cf5278c4c46b8bac89068dc1ae5f22d5ed5229)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fk59%2Fdawnskaybug%2FIMG_0201.jpg&hash=2e15ca44e746550fabac7136d8125756fc2659df)
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Looks way too much for a FWD car. The drag must be terrible too!
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Awesome pics Bruce. Do you know the chord and span of those wings ?
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Ha ha... I also saw the Scirocco Cup cars in last August.
The rear wing is not adjustable and the chord seems to be somewhere around 150 - 170.
Personally I do not like those rear wings.
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Sadly I have no specific data. :confused: They seem to have these huge wings now. In their first season
the Cup Roccos just had the small Votex Wing. I guess VW Motorsport know what they're doing.
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9) Rear wing:
If you don't want to fit a huge wing some roof spoilers may be a less efficient but
more elegant alternative:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328212927_3041.jpg&hash=d230c62705d9e7f6f0a67e6e09ba2a43dc682c4c)
> www.vary.co.jp
....I can't find that carbon add-on roof spoiler on the 'vary' Jap link. Do you have any other info, please?
It looks less 'in-yer-face' than the OSIR rear roof spoiler.
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http://www.vary.co.jp/
First click on the 'Golf picture' above, then on 'Golf 5 GTI'. After that you will be here: :wink:
http://www.vary.co.jp/reife/golf5_gti.html
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.vary.co.jp%2Freife%2Fgolf5_gti%2F11.jpg&hash=fd809c10409838b4cf7a2b9ec6416485115c9ad2)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.vary.co.jp%2Freife%2Fgolf5_gti%2F10.jpg&hash=cbfe56f77e7b9654f184f743d065f25c90890ec5)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.vary.co.jp%2Freife%2Fgolf5_gti%2F12.jpg&hash=64d3f0469b3355b2893ac8c8cf4e7156dcbf0f1f)
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^^^^
Thanking You!! :drinking:
Now where can I get one!? (if not too expensive). I don't really need one but I don't really need some of my other mods either.
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Thanks bruce so no under body fuel tank makes that much easier to fit a panel under there as the standard one the tank dips below where the panel would be :sad1:
ATL Fuel Cell - keep in mind it's a diesel.
http://www.erft-racing.de/fahrzeug.php
http://www.erft-racing.de/galerie_bilder.php
Unfortunately I couln't fid any additonal pics that show the underside, but I guess the above pic
shows most you need to know.
:drinking:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fhighspeedfotos.de%2FCoppermine%2Falbums%2F242009Corso%2F24h2009RCN109.jpg&hash=1bc51292f424512bb84ef049597c23ab8cb07399)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Flh5.ggpht.com%2F_i1GUNpeTgoc%2FSmQR-fJfEtI%2FAAAAAAAAa0I%2Fs4HIsQAKB14%2Fs720%2FIMG_3213.jpg&hash=26390a7ebefac4d7ef10404bf9c6462c37d3b3d9)
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The tank isn't the problem, Ric, but rear exhaust + lower arms are. :fighting:
-
Bruce is right but for an efficient diffuser it depends how much further away from the rear bumper you want to go. As the slope/angle is constant (I've read 10-12deg would be best), if you want to make a rear diffuser that extends to the rear wheels, you need to either start the diffuser very low, either reach a high point on the bumper. The diffuser needs to be trimmed around the rear arms as they need to be able to move up-down while the car is on a ramp !
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Hi bruce it is the problem in front of the rear control arms, where I have fitted the larger stone guards backwards is a very messy area that I want to clean up as well as the area across the rear muffler.
I know you guys are after extra down force but i think this is difficult so I think first and to keep the car looking oem the first task is to try and further smooth off the underside of the car as much as can be.
I have some small panels that I want to try over the exhaust and area by the fuel filter as the fuel tank blocks the are in the centre, what I really want is a larger panel to run from the rear axle mounting points I have them on both sides for the pass at panel with cut outs for the suspension arms over the exhaust and finally mount on the rear bumper to fit flush with the tiny lip I think this will give a smoother air flow and hopefully improve the aero up to higher motor way speeds beyond the existing blue motion panels. And the shape I think will have some diffuser qualities such as an expansion to slow the air.
Aluminium can also touch the exhaust without fear of melting and can act as a heatsink.
-
Need to get myself a new bluemotion undertray :sad1:
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the bruce this ones for you
never thought id say it but i really want a volvo!
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fh456%2Felbowsg450x%2F4e81386d.jpg&hash=bf4c5e7b6034bd5c501bcc1f719eabc89202b1b8)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fh456%2Felbowsg450x%2Ffb371a7f.jpg&hash=035a3a51b7d401ffa9ed99c3682521fb8341e983)
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Thank you Ken, have your pics on the other forum.
Did you have a view at the underbottom?
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no i didn't sorry. it was flat though but no large rear diffuser
-
I will probably go with a Reverie wing but have 4 options at this point :
Chord > 150 ; Span > 1250 ; Downforce @ 160kmh and AOA of 10deg > 380N ; BHP absorbed > 2.9
Chord > 150 ; Span > 1400 ; Downforce @ 160kmh and AOA of 10deg > 427N ; BHP absorbed > 3.2
Chord > 225 ; Span > 1250 ; Downforce @ 160kmh and AOA of 8deg > 574N ; BHP absorbed > 5.1
Chord > 225 ; Span > 1400 ; Downforce @ 160kmh and AOA of 8deg > 617N ; BHP absorbed > 6.3
1) To convert to kg we need to divide by 10, so for ex. 380N = 38kg
2) Those figures are in a freestream of air wich means on our car they will be smaller. Also the extremes of the wing wich hang out of the car's limits are the most efficient so in reality, the difference between 1250 and 1400 might be larger. The car has about 1050 at the upper side of the trunk lid, wich means a 1250mm wing will stick out 100mm on each side, while a 1400mm will stick out 175mm on each side !
The wings will be straight and will have endplates of course ! From what I could approximate on Supercopas and other similar racing hatchacks their wings seem closer to 150mm but they also have diffusers to help them with downfoce. From the Golf 5 GTI aerodynamic data presented earlier, the rear had a lift of 37kg @ 200kmh wich will probably be like 25kg @ 160kmh.
How would you guys judge this problem and what would you choose ?
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I guess your thoughts are right. All these wings work. If you don't care about top
speed go for the 225 chord wings and choose span due to your taste.
You will also play with different angles and even with wing position. If rear DF seems
to be too much you decrease wing angle or probably even wanna add a front splitter
to the VWR spoiler.
-
i have the S3 engine shield
im considering bluemotion exhaust and tank and rear axle shields
do these make a real difference or is it just in the head do you think?
-
wrong thread, Ken. Choose one of these:
http://www.mk5golfgti.co.uk/forum/index.php/topic,22986.msg306740.html#msg306740
http://www.golfmkv.com/forums/showthread.php?t=163575
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diffuser parts:
http://www.elise-shop.com/aerodynamicabody-c-6_75.html
brake vent parts:
http://secure.chassisshop.com/categories/6013/
http://butlerbuilt.net/2010_Tree/products_Air_Managment_Systems_Ducts.html
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Interesting option:
fitted my cupspoiler :evilgrin:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fbuzz1231%2Fcupra%2FDSC_0988.jpg&hash=b6be38feb313c33c85795e31b6a1cb2dfa2a45da)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fbuzz1231%2Fcupra%2FDSC_0990.jpg&hash=e92a351d69efab9bbbbda22b59b7d13a4687e861)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fbuzz1231%2Fcupra%2FDSC_0992.jpg&hash=3cc80280b7a603d2d66f39382c1981642c96e97e)
I know - he's not the only one. :wink:
But - does it fit to the Golf ???
.
-
^^^^
Thanking You!! :drinking:
Now where can I get one!? (if not too expensive). I don't really need one but I don't really need some of my other mods either.
ON their sit it gives prices
FRP wing tip £47
Carbon Tip £282
-
^^^^
I don't know why I'm thanking you, Miles! (I hope it is Miles and not Myles)
I don't want to spend £282 on a small bit of carbon just for styling.
-
^^^^
I don't know why I'm thanking you, Miles! (I hope it is Miles and not Myles)
I don't want to spend £282 on a small bit of carbon just for styling.
Same goes, If I wont spend money on brakes I am not likely to be spending money on a wing tip :signLOL:
It is Myles btw :grin: :grin:
-
It is Myles btw :grin: :grin:
....I can remember that: It's Myles as in Tamiyoman :happy2:
-
Ok, my wing is here and I sent it for custom mounting it on the car. Follow up on my thread in a few minutes !
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Time for some updates. Took the car from my mechanic abouth 1 month ago and it's working fine, except for the same rough idle who seems to never go away. There's some sort of a cyclic noise at idle and don't know why but while on the road the car behaves normally. Didn't have the change to WOT it yet but will do it after installing the wing....wich reminds me of the second update :)
The custom Reverie wing came and it's very well manufactured. After talking to Reverie guys, they advised me to go for the smaller 150mm profile instead of the 225mm one. They said it should be enough for a FWD car and that a larger one would ruin the balance of the car unless I also have a large splitter in front. The wing was made with a span of 1300mm and a 515mm distance between the drop tabs. After speaking to the guy designing the mounts, he said we can't use the car's hinges of the trunk lid so I've distanced the tabs 50mm from the hinges on each side. Didn't weigh the wing yet but it seems to be about 7-800grams only !!!
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimageshack.us%2Fa%2Fimg33%2F5043%2Freverie8.jpg&hash=6abdd0f4cbc6549200cf8562b231ae8f6aa59f8e) (http://imageshack.us/photo/my-images/33/reverie8.jpg/)
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(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimageshack.us%2Fa%2Fimg688%2F2443%2Freverie10.jpg&hash=2c0cc7234e325efbbc7fc693114de04654cb04d0) (http://imageshack.us/photo/my-images/688/reverie10.jpg/)
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(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimageshack.us%2Fa%2Fimg407%2F4567%2Freverie12.jpg&hash=9b84a925ec01bdb7d13c64162198b905f666efd3) (http://imageshack.us/photo/my-images/407/reverie12.jpg/)
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(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fimageshack.us%2Fa%2Fimg528%2F8406%2Freverie13.jpg&hash=079d62bbd9a2ba73fe8a407c2e91ab3a6fbb5a8e) (http://imageshack.us/photo/my-images/528/reverie13.jpg/)
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By interpolating between 1245 si 1400mm, at an AOA of 10deg, we get about 43kg@100mph. From an older post over here, the wind tunnel says the OEM GTI has -2kg on front si -37kg on rear @ 200kmh. Those values mean the car has lift at high speeds(but then again most street car have lift). Knowing I'm lowered about 1'' and I have the VWR front air-dam, the real values on my car might be a little better, say +5kg on front and -30kg on rear. In order to compare the downforce brought by the wing and the values we have for the OEM car, we need to calculate the wing's value @ 200kmh. 43kg*(200kmh2/160kmh^2)^ = 67kg . So, at 200kmh, the car should have about 0 to 5kg of downforce on front and 30-35kg on rear (67-30 = 37 but I'm considering less because the wing's data has been acquired under freestream and not disturbed air like on the car) !
PS : For those wanting to compare the downforce level of a track-prepped street car and an F1 car, at 200kmh I would have about 1450kg and 40kg of downforce (2.8% of the car's mass) and a formula 1 car would have about 700kg and 1400kg of downforce (200% of the car's mass !!!). I think it's easy to understand how an F1 car can generate such tremendous downforce levels, knowing that the downforce does not generate inertia !
:happy2: :happy2:
Can't resist to add that to this topic. :wink:
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interesting find:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.stri-racing.com%2Fmedia%2Fcatalog%2Fproduct%2Fcache%2F6%2Fimage%2F9df78eab33525d08d6e5fb8d27136e95%2Fg%2Fo%2Fgolf_6_middle_skid_diffusor_plate.jpg&hash=f913c472870aad4ee8e41bdb7cfe35442cc849d2)
http://www.summit-racing.eu/homepage/center-cooling-panel-diffuser-vw-golf-vi-11.html
We already know this:
http://www.nengun.com/garage-vary/vw-golf
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The flat bottom is very interesting but way too expensive !
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Is that fitted on top of their Summit-Racing braces?
Summit have totally missed the structural 'X' factor advantages which the UNIbrace UB has. Personally I would far rather have the added stiffness of a UNIbrace than this aerodynamic 'improvement' which anyway doesn't convince me as being worthwhile on a Golf.
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It's worth Robin but only if you want to extract the last bit of performance on the car and probably if you also add a diffuser !
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From what I see that car also has a Unibrace fitted.
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From what I see that car also has a Unibrace fitted.
....Are you sure? Wouldn't they have fitted their own Summit cross braces?
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From what I see that car also has a Unibrace fitted.
....Are you sure? Wouldn't they have fitted their own Summit cross braces?
Yes, there's a bit of it to be seen on the left and right of the tunnel.
On a side note: You might also find some inspiration here:
http://www.mk5golfgti.co.uk/forum/index.php/topic,59674.msg669054.html#msg669054
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Interesting how they designed the brackets:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.smp-motorsport-fotos.de%2Fimages%2Fvln-7tes_saisonrennen-6h_adac_ruhr-pokal-rennen-nuerburgring_2010_07_31%2Fvln-7tes_saisonrennen-6h_adac_ruhr-pokal-rennen-nuerburgring_nordschleife_schwalbenschwanz_055.jpg&hash=a5696a155cfe41f92a6085a6c16d4a6afbc1057c)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.smp-motorsport-fotos.de%2Fimages%2Fvln-7tes_saisonrennen-6h_adac_ruhr-pokal-rennen-nuerburgring_2010_07_31%2Fvln-7tes_saisonrennen-6h_adac_ruhr-pokal-rennen-nuerburgring_nordschleife_schwalbenschwanz_005.jpg&hash=aae5acd95166e619308534ba4b5cdc6ff1743bca)
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Interesting how the designed the brackets:
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.smp-motorsport-fotos.de%2Fimages%2Fvln-7tes_saisonrennen-6h_adac_ruhr-pokal-rennen-nuerburgring_2010_07_31%2Fvln-7tes_saisonrennen-6h_adac_ruhr-pokal-rennen-nuerburgring_nordschleife_schwalbenschwanz_055.jpg&hash=a5696a155cfe41f92a6085a6c16d4a6afbc1057c)
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.smp-motorsport-fotos.de%2Fimages%2Fvln-7tes_saisonrennen-6h_adac_ruhr-pokal-rennen-nuerburgring_2010_07_31%2Fvln-7tes_saisonrennen-6h_adac_ruhr-pokal-rennen-nuerburgring_nordschleife_schwalbenschwanz_005.jpg&hash=aae5acd95166e619308534ba4b5cdc6ff1743bca)
Seems they are trying to get the wing out in more undisturbed air
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^^^^
Thanking You!! :drinking:
Now where can I get one!? (if not too expensive). I don't really need one but I don't really need some of my other mods either.
Was thinking the same thing in fact i dont even want it in carbon. :party:
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Yes, I told fuscobal to keep the templates so it will be easier to have a wing mounted later on.
I also want to have a rear diffuser but this is a costly job since I want to change the whole exhaust with the new diffuser.
But both these chapters require spending money and I prefer to spend the money on going to Hungaroring and/or Nurburgring instead. There is enough time to do all the mods...
The biggest challenge is you need to remove the rear exhaust muffler. This implies to
content oneself with a center muffler or even without any at all.
The diffusor itself is made with just some cheap parts (you already know this example):
(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fwww.golf5gti.com%2Fupload%2Favatars%2Futool_f_1328211420_3041.jpg&hash=79e98d4abc931d2a60ce6f848265089a247e8c66)
The big advantage of a diffusor is it provides downforce without any drag penalty worth
mentioning (which a wing has besides the cost).
BTW, there's another 'cheap trick' which cannot substitute a wing, but will at least reduce
lift by some 10 N (at 200 km/h): a gurney flap. It's easily made by some piece of plastic
and fitted to the roof spoiler before you visit a track.
Unfortunately most of the known literature depends on mounting a gurney flap to wings.
Nevertheless it also works on a rear spoiler.
http://en.wikipedia.org/wiki/Gurney_flap
http://www.insideracingtechnology.com/tech104gurney.htm
http://www.dept.aoe.vt.edu/~mason/Mason_f/AIAA2007-4175.pdf
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Yup, I know about that diffuser. That is my template also at the moment.
I know I have to get rid of the rear exhaust muffler, that is why I want a new complete exhaust.
Interesting read about the gurney flap.
As I can see it is even used on the diffuser above...
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Good findings on the gurney flap. MAybe I'll make one on my wing as well. Let's take my wing and make some small assumptions :
- Wing > Reverie 150mm chord with 1300mm span
- Desired gurney flap > 1.25% to 5% of chord, meaning 1.875mm to 7.5mm (these are quite small and barely visible on the car)
- Downforce @ 160kmh & 12deg AOA with no gurney > 45kg
- Downforce @ 160kmh & 12deg AOA with 1.875mm gurney > +20-30% wich means about 54 to 58.5kg ( 9 to 13.5kg increase !!!)
- Downforce @ 160kmh @ 12deg AOA with 7.5mm gurney > +40-50% wich means about 63 to 67.5kg ( 18 to 22.5kg increase !!!)
If these values (taken from the last link Bruce provided) are not highly optimistic, then the downforce addition from these small devices is tremendous and easy to achieve !
It seems that I did not pay attention while ordering the wing since they also have carbon 5mm and 10mm gurney flaps available for 90-130L)
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According to Joseph Katz:
From an aerodynamic standpoint when on track with a production car rear downforce is
by far most important, then front DF and drag is neglicible. Even more with a Golf which
has more rear lift than most sedan style cars.
Rear DF allows for a more aggressive suspension setup which will help on small radius
corners (where you don't have DF worth mentioning).
Well, the gurney flap is one of the very few parts invented first in automotive racing (by
Dan Gurney) and then established in aviation. In the latter case such flaps are just needed
on take off and landing. On journey low drag and highest possible efficiency is what plane
designers are seeking for.
Contrary to this at car racing drag is nothing reace car designers worry that much. Most
prototype racers have a Cd of 0.7 to 0.8, open wheel cars have even more.
Even production car based racers have much more drag compared to it's stock brothers
(which as you all know are in the 0.25 to 0.35 area today).
Highest downforce you can get is faster than highest possible efficiency. That's the point.
This is why the same applies to a wing on a car. Downforce is more important than efficiency.
While you get the best efficiency with a wing without a flap a wing with a gurney flap will
give you more downforce at higher angle of attack without stall. Stall will occur later than
without the gurney.
Conclusion: It's better you fit a gurney if you want the most DF (and you will want DF).
There are some not-so-expensive CF lips on ebay, but any black plastic profile which is
not too brittle will do. Just take care to fit it to the upper (high pressure) side. No part of
it should disturb the flow on the lower (low pressure) side of the wing.
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Yes, seems pretty clear I should add it. At 1-2% of chord the gurney adds no drag enalty at all and at 2-5% it adds increasing drag but still nothing to worry about if you compare to what it brings. I've read some technical papers and it seems that a 4-5% of chord gurney can add up to 40% downforce. For me, even adding a conservative 25% would mean about 10-12Kg @ 160kmh ! Not bad at all !
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Did some approximations on the real downforce level with my wing at max downforce position. For this I used the following data :
- OEM car rear lift > 37kg @ 200kmh (as posted by Bruce some time ago from a wind tunnel test)
- Reverie wing downforce > 30kg @ 160kmh (could be 35 but better be conservative so let's say it's 30)
- I've considered a 25% downforce addition from a gurney flap wich is 4-5% of the wing's chord
- Formula used to extrapolate from the 2 values I have was DF @ new speed = DF @ old speed x (new speed ^ 2 - old speed ^ 2) wich mean practically downforce increases with the square of the speed
Speed in kmh > Stock lift > Wing DF > Total 1 (Wing DF - Stock lift) > Wing + gurney DF > Total 2 (Wing + gurney DF - Stock lift)
80 > 5.92kg > 7.50kg > 1.58kg > 9.38kg > 3.46kg
100 > 9.25kg > 11.72kg > 2.47kg > 14.65kg > 5.40kg
120 > 13.32kg > 16.88kg > 3.56kg > 21.09kg > 7.77kg
140 > 18.13kg > 22.97kg > 4.84kg > 28.71kg > 10.58kg
160 > 23.68kg > 30kg > 6.32kg > 37.5kg > 13.82kg
180 > 29.97kg > 37.97kg > 7.99kg > 47.46kg > 17.49kg
200 > 37kg > 46.88kg > 9.88kg > 58.59kg > 21.59kg
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If there is stock lift and wing dowforce, in order to see the benefits you should add the 2 values (or improvement = WingDonwforce - ( - Stock lift)).
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Lift and downforce have opposite directions so you simply add them (one is vertical up and has -, the other is vertical down and has +). The bolded values are the final result wich is a small amount of downforce, knowing the wing bring a little more downforce @ a certain speed thn the lift of the OEM car @ same speed !
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First: Think we should a link here to your pictures:
http://www.mk5golfgti.co.uk/forum/index.php/topic,12484.msg698714/topicseen.html#msg698714
To me it's better to read this way:
speed >>> stock lift >>> wing DF >>> Total 1 >>> wing + gurney DF >>> Total 2
in km/h . . . . . . . . . . . . . . . . . . . . . (wing DF - stock lift) . . . . . . . . . . . (wing + gurney DF - stock lift)
80 >>>> +5.92 kg >>>>> -7.50 kg >>> -1.58 kg >>>>> -9.38 kg >>>>> -3.46 kg
100 >>>> +9.25 kg >>>> -11.72 kg >>> -2.47 kg >>>>> -14.65 kg >>>>> -5.40 kg
120 >>> +13.32 kg >>>> -16.88 kg >>> -3.56 kg >>>>> -21.09 kg >>>>> -7.77 kg
140 >>> +18.13 kg >>>> -22.97 kg >>> -4.84 kg >>>>> -28.71 kg >>>>> -10.58 kg
160 >>> +23.68 kg >>>> -30.00 kg >>> -6.32 kg >>>>> -37.50 kg >>>>> -13.82kg
180 >>> +29.97 kg >>>> -37.97 kg >>> -7.99 kg >>>>> -47.46 kg >>>>> -17.49 kg
200 >>> +37.00 kg >>>> -46.88 kg >>> -9.88 kg >>>>> -58.59 kg >>>>> -21.59 kg
Added a '+' to the lift values and a '-' to the downforce ( negative lift) values.
Most interesting - What to conclude?
I'd guess depending on track most important turns are between 80 and 140 km/h. I'd say:
1.
At 80 km/h it may be of lesser significience if you have 6 kg of lift on rear or 3.5 kg DF.
2.
At 140 km/h it definitely matters if you have 18 kg lift or you have a downforce of 10.5 kg
instead, even more if you turn in and have still your foot on the brakes.
3.
If you apply the brakes at the end of start/finish rear grip will be vastly improved.
37 kg lift compared to 22 kg downforce - it's a difference of almost 60 kg at a moment when
dynamic corner weights are often below 100 kg !!! Rear wheels now have a chance to take
part of deceleration.
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Oh, fuscobal, now I understand... We were both right!
You were calculating the DF you have at various speeds and I was looking to see the gains over the stock setup...
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Rex, gain over stock is exactly the columns wing df or wing + gurney df :)
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Interesting...had a discussion with Simon from Reverie today and looking at my pics he said my wing is almost in freestream and there is no way that I lose 25% of the downforce as compared to freestream. He said I may lose very little or nothing. In this case it's safe to replace the 30Kg value with a 40kg value !!!
speed >>> stock lift >>> wing DF >>> Total 1 >>> wing + gurney DF >>> Total 2
in km/h . . . . . . . . . . . . . . . . . . . . . (wing DF - stock lift) . . . . . . . . . . . (wing + gurney DF - stock lift)
80 >>>> +5.92 kg >>>> -10.00 kg >>> -4.08 kg >>>>> -12.5 kg >>>>> -6.58 kg
100 >>>> +9.25 kg >>>> -15.63 kg >>> -6.38 kg >>>>> -19.53 kg >>>>> -10.28 kg
120 >>> +13.32 kg >>>> -22.5 kg >>> -9.18 kg >>>>> -28.13 kg >>>>> -14.81 kg
140 >>> +18.13 kg >>>> -30.63 kg >>> -12.49 kg >>>>> -38.28 kg >>>>> -20.15 kg
160 >>> +23.68 kg >>>> -40.00 kg >>> -16.32 kg >>>>> -50.00 kg >>>>> -26.32kg
180 >>> +29.97 kg >>>> -50.63 kg >>> -20.66 kg >>>>> -63.28 kg >>>>> -33.31 kg
200 >>> +37.00 kg >>>> -62.50 kg >>> -25.5 kg >>>>> -78.13 kg >>>>> -41.13 kg
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Revised my conclusion: :wink:
1.
At 80 km/h it may be of lesser significience if you have 6 kg of lift on rear or -6.6 kg DF.
2.
At 140 km/h it definitely matters whether you have 18 kg of rear lift or you have -20 kg
of downforce instead, even more if you turn in and have still your foot on the brakes.
3.
If you apply the brakes at the end of start/finish, rear grip will be vastly improved.
37 kg of lift compared to -41 kg of downforce !! This is a difference of almost 80 kg at
a moment when dynamic corner weights are often below 100 kg !!!
With such a wing rear wheels of a FWD now have a chance to take part of deceleration.
again: :happy2:
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Simon McBeath states in his book that a 2005 BTCC car has 1150kg and 38.9 to 61.9kg of downforce (3.4 to 5.4% of weight). By comparison, a LMP3 car has 605kg and 230.2 to 291.1kg of downforce (38 to 48.1% of car's weight)