aerodynamics - better feel, increased efficiency

[the bruce]

Let's talk about aerodynamics and have a look at serious some sportscars and current Golfs.


("Auftrieb" = lift; "Abtrieb" = downforce)


Some Porsches first:


997 II GT3:

downforce: 152 Newton front and 186 Newton on rear

http://www.sportauto-online.de/bild...332080.html?fotoshow_item=15#fotoshow_item=16



2006 GT3:

http://www.sportauto-online.de/supertest/porsche-911-gt3-auf-der-rennstrecke-nuerburgring-hockenheim-1040952.html

[img]http://img4.sportauto-online.de/image-fotoshowImage-348acdd3-220043.jpg

2007er Vergleich zwischen GT3 und GT3 RS:

http://www.sportauto-online.de/supe...ser-denn-je-der-neue-porsche-gt3-1345012.html



2007 GT3 RS:

http://www.sportauto-online.de/bild...041046.html?fotoshow_item=10#fotoshow_item=11

rear downforce 100 N > 10 kg/22 lbs.



2011 GT3 RS:

@ 200 km/h downforce:
front 110 N
rear 490 N
(due to RSR-style wing)

M3 E92:

(A): 2.170 m²
(cw): 0.33
(cw × A): 0.71
front: 100 N lift
rear: 230 N lift

Some Golfs and similar cars:


Golf Mk.VI GTI Edition 35:

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)



Golf Mk.VI R:

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)



Golf Mk.V GTI:

Aerodynamische Balance

* A: 2.23 m²
* cw: 0.33
* index (cw × A): 0.74

* VA: 2 kg Auftrieb
* HA: 37 kg Auftrieb

bei 200 km/h (!!!)

Golf R32:

3 kg Auftrieb an der VA und 36 kg an der HA

All Golfs (mk.V + Mk.VI) have surprisingly low lift on front. Sadly lift on rear is significient ans also drag.



Audi TT:

Lift 23 kg front and 24 kg rear (Spoiler at lift position).

Audi RS3:

Fahrzeugstirnfläche (A): 2.180 m²
Luftwiderstandsbeiwert (cw): 0.36
Luftwiderstandsindex (cw × A): 0.78
Vorderachse: 21 kg Auftrieb, Hinterachse: 1 kg Abtrieb
.



Ford Focus RS:

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:

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)


http://www.sportauto-online.de/supe...-wird-zum-porsche-schreck-3383831.html?show=2


The Scirocco R Cup has downforce of 200 N (~ 20 kg) @ 200 km/h: :thumbsup:

Stock Scirocco:

Stirnfläche (frontal area A): 2,14m²
cw-Wert (drag coefficient cd): 0,34

>> 2,14m² x 0,34 = 0,73m²

Scirocco: 0,73 m² > Golf: 0,68 -0.75 m² > S-Class: 0,65 m²

CONCLUSION:


While the GTI (both Mk.V and Mk.VI) has very low front lift, it has some significient rear lift
and mediocre drag.
Rear lift causes unsettling when braking friom higher speeds, drag increases fuel consumption.



http://www.golfmkv.com/forums/showthread.php?t=163575



All you need to reduce both rear lift and drag by some amount:

Between fuel tank and rear exhaust there's the ''Hinterachsverkleidung'' = rear axle cover.

part number 1K0 825 237 P:

1K0 501 713 D Trim for Rear Axle:

There are even some more, but these are the easiest to install parts:

Engine undertray
1K0 825 237 P Noise Insulation
1K0 825 951 Hex headed bolt (need 3)

Rear axle cover as fitted to bluemotion
1K0 501 713 D Trim for Rear Axle (EDIT: substituted by 1K0 501 713 E )
1K0 501 682 Retaining bracket
N 905 483 05
N 901 838 02

available at ECS etc.


installation guide (german):

http://www.golfvigti.com/attachment_processor.php?mode=download_file&id=1485

 

[Stampedevxl]

hope this part isnt very important cuz i dont think any lowered gti owners keep that lol

 

[the bruce]

It isn't really lower than the subframe.

The three lowest parts are:

- front subframe
- small underbody spoilers
- rear lower control arms


these are the little spoilers every Golf and GTI from factory comes with
and I touched the ground several times with:

this is the big engine bay undertray I recommend and you can easily see
the subframe is still the lowest part on front:

alternatively VW and ECS sell this steel belly pan:

 

[ik1015]

Trim for rear axle is more than $110 in here...front is cheapest under $70+shipping.

1K0 501 713 E Trim for Rear Axle is same?

 

[the bruce]

THX !!

Just a new revision of the same part.

 

[Stampedevxl]

It isn't really lower than the subframe.

The three lowest parts are:

- front subframe
- small underbody spoilers
- rear lower control arms


these are the little spoilers every Golf and GTI from factory comes with
and I touched the ground several times with:

http://up.picr.de/13924554hh.jpg[img]


this is the big engine bay undertray I recommend and you can easily see
the subframe is still the lowest part on front:

[img]http://up.picr.de/13924555zq.jpg[img]


alternatively VW and ECS sell this steel belly pan:

[img]http://up.picr.de/13924556md.jpg[img][/QUOTE]
yeah those little spoilers are worn off on my car and the belly pan is just a PITA, like ive dropped a socket or tool and then have to jack up the car and remove like 10 screws... screw that!

 

[VancouverGTI]

I would think that running at high speeds without that belly pan could cause lift... and perhaps a lot of it.

 

[Bunnspeed]

How much do these underside bits impact upon road noise? There might be some benefit to packing em full of Dynomat before bolting them on.

 

[LondonGT]

Are these available parts not fitted or are they bits some cars don't have?

I'm confused and it doesn't take much.

I have an edition 30 rear bumper and votex splitter. I have found these have really made a difference on the road, especially motorway, but anything to assist and I'm all ears.

Thanks

 

[Bunnspeed]

How much do these underside bits impact upon road noise? There might be some benefit to packing em full of Dynomat before bolting them on.

Bump. I'd still love to know the answer to this question. :thumbsup:

 

[zrickety]

I don't see the metal undertray on ecs. Part number??

 

[zrickety]

Has anyone bought the metal 'noise insulation,' or undertray?