aerodynamics?

[junker]

Airflow through the open grills don't reach the brakes without modification, so the air through them is running into a wall for the most part.

Originally Posted by anile_eight

The open fogs if we are talking about the same thing... The ones that are used to vent air to the brakes? Are you wanting a comparison of that to ones that are completely blocked off? Well risking hot brakes, yea they would help maybe 1 mph for top speed and maybe again a percentage point for mpg increase. But for the track, no one in their right mind would do that.

[junker]

Not sure this is as much about downforce as it is about reducing the coefficient of drag in the same vein as the dimpled undercarriage panels.

I do not have the rear bumper so a lot of air is running directly into my rear valence. I'm looking forward to see if the rear axle shield routes air under the rear valance.

Originally Posted by anile_eight

I AM an aerospace engineer specializing in aerodynamics... for those who don't know too much most of the simple mods aren't very useful or probably a better word significant for autoX. Typical speeds are around 40-50mph in a straight line with most courses not having high speed turns. Yes, a smooth undercarriage would help with a splitter and rear wing but at these speeds the addition of down force and weight virtually cancels out. You may squeeze a thenth or two out and if that is what you are looking for great, but don't expect much beyond that. Tires, and diver make the biggest difference among other setup tweaks. Most of this stuff would be better suited for track days ... just my 0.02

[anile_eight]

Originally Posted by junker

Airflow through the open grills don't reach the brakes without modification, so the air through them is running into a wall for the most part.

Yes, you are correct but there is still the slit below and path for the air to go through so it's not quite a wall but yes it increases drag.

Originally Posted by junker

Not sure this is as much about downforce as it is about reducing the coefficient of drag in the same vein as the dimpled undercarriage panels.

I do not have the rear bumper so a lot of air is running directly into my rear valence. I'm looking forward to see if the rear axle shield routes air under the rear valance.

The coefficient of drag of the GTI is 0.32, so 320 drag counts which in airplane terms for a GA aircraft is almost 10 times the avg. A lot would need to be done to alter this number. What goes into drag (basically) is form drag (how the object physically looks and the drag cause ONLY by it's shape), skin friction (exactly how it sounds) how smooth is it's surface. *(See note below) and lastly induced drag which is the drag induced from lift or in this case the downforce (negative lift)

Again, if you can smooth out the undercarriage that would probably help out in the long run especially for long range cruise, just keep it as light as possible.

NOTE* The dimpled surface allows for a turbulent boundary layer which is also thicker which "adheres" to the surface longer as it has more energy thus allowing for a smoother flow over the entire body. This tried to help the air under the car be as smooth as possible.

[the bruce]

Originally Posted by anile_eight

The open fogs if we are talking about the same thing...

I guess there's an increase in drag, but not that much at all.
On my own car I'd only fit them if I really need more brake ventilation.

[anile_eight]

Either way, unless it's a completely smooth front end, it really won't make much of a difference.

[daigo]

Took off fog lamps, pulling airducts from fog grille hole.

[the bruce]

Just a few examples:


DIY:


DIY not-so-nice:


DIY fog grill:


RS3/TT-RS element:



Mini Mania kit:




I have removed the dust shield and fitted the RS3 elements.

[junker]

Here is a comparison picture of the large underbody engine-transmission cover versus the stock unit.

I've also attached a picture of it installed so you can see the contour in it under the transmission.

[762]

Originally Posted by anile_eight

I AM an aerospace engineer specializing in aerodynamics... for those who don't know too much most of the simple mods aren't very useful or probably a better word significant for autoX. Typical speeds are around 40-50mph in a straight line with most courses not having high speed turns. You may squeeze a thenth or two out and if that is what you are looking for great, but don't expect much beyond that.

Just need to address this. National championships or trophies are decided by just such tight margins. If your class allows aero, then it is important.

autox specifically can gain a ton from aero in a unique way. You need an autox car to have ultimate mobility in low speed elements. This requires a trade off of making the car less stable at high speeds. In fact your setup is often driven by your preference on where to be fast. Even minor aero such as a S2000 CR splitter or wing plays just enough of a role to allow me to loosen the car up a touch more at low speed and not compromise high speed stability at 50 mph when the car starts getting the aero effects to compose the car.

Aero is certainly not the first thing to deal with when tuning but even at autox speeds it will make you faster.

[daigo]

Originally Posted by the bruce

Just a few examples:

RS3/TT-RS element:


I have removed the dust shield and fitted the RS3 elements.

I never knew RS3/TT-RS wind reflector!
Seems it works so well. I think I'd better get one. Thanks.

[the bruce]

Hello Daigo,

I have these fitted. With S3 alloy arms (RS3 has the same) + TT-RS or GTI calipers fitment is plug & play.
With steel arms there may be some minor cutting (to the plastic shield) required. Also with S3/R32 calipers.

I already posted the part number on another thread. I will have a look for them if you can't find them.

[anile_eight]

Originally Posted by 762

Just need to address this. National championships or trophies are decided by just such tight margins. If your class allows aero, then it is important.

autox specifically can gain a ton from aero in a unique way. You need an autox car to have ultimate mobility in low speed elements. This requires a trade off of making the car less stable at high speeds. In fact your setup is often driven by your preference on where to be fast. Even minor aero such as a S2000 CR splitter or wing plays just enough of a role to allow me to loosen the car up a touch more at low speed and not compromise high speed stability at 50 mph when the car starts getting the aero effects to compose the car.

Aero is certainly not the first thing to deal with when tuning but even at autox speeds it will make you faster.

Oh, no I agree, and I have seen such things as well. I have had a guy approach me to design him a multi-tear rear wing for his miata for the autox here... It will have to be a high camber rather tall wing. But After more research he decided against it as he would get bumped a couple classes and would lose his edge.

[LOUCFUR]

Originally Posted by junker

Here is a comparison picture of the large underbody engine-transmission cover versus the stock unit.

I've also attached a picture of it installed so you can see the contour in it under the transmission.

did you buy all of the pieces mention or just this one? ...

[miamirice]

Originally Posted by anile_eight

Oh, no I agree, and I have seen such things as well. I have had a guy approach me to design him a multi-tear rear wing for his miata for the autox here... It will have to be a high camber rather tall wing. But After more research he decided against it as he would get bumped a couple classes and would lose his edge.

I love the auto cross Miatas with the windshield structure gone. I can never figure if they cut it off or bought a rolled donor.

[LOUCFUR]

heres a question for you guys. (and it doesnt mean i to do it). just wondering what design would give more downforce in the rear.

would a solid rear spoiler be more effective than one that lets air go through?

heres some examples :

solid http://www.ebay.com/itm/10-VW-MK-6-V...cb016c&vxp=mtr

not solid http://www.ebay.com/itm/09-12-VW-GOL...0e57d9&vxp=mtr

or a spoiler that curves up like osir http://www.osirusa.com/mm5/merchant....ry_Code=VGTIEB

i watch the wrc. and all the cars have that giant wings that lets air go through ...

[junker]

Originally Posted by LOUCFUR

did you buy all of the pieces mention or just this one? ...

For chassis aero I bought the under engine cover, axle cover, and reverted to only running the passenger open vent.

The front underbody engine cover was ordered from 1stwvparts. Be sure to get the 3 sub-frame bolts for it. Tip: Don't tighten anything down until all of the torx screws are threaded.

The Rear axle cover and bracket were ordered from ECS. The bracket hardware was ordered from 1stvwparts.com. I'll get a better feel for this part after install, but I'm more interested in running air under the rear valence with the lack of a suitcase muffler than I am about smoothing air flow over the axle.

Then, as far as brakes go... I am going to consider this an entirely different toptic and will be starting a seprarate thread in a few weeks after some stuff comes in from Japan and Germany so stay tuned! That install will be part of a major brake upgrade in a few weeks. The RS3 vents will be coming in from Germany using WorldImpex.com. I can't stand having not pedal feel or feedback until the brake pedal is level with the accelerator.

You can always check what I have done, and usually what I am working on in My Garage. It's the only way for me to keep track of everything I've done to date on project MindMeld so far...

[RRacerguy717]

Originally Posted by LOUCFUR

heres a question for you guys. (and it doesnt mean i to do it). just wondering what design would give more downforce in the rear.

would a solid rear spoiler be more effective than one that lets air go through?

heres some examples :

solid http://www.ebay.com/itm/10-VW-MK-6-V...cb016c&vxp=mtr

not solid http://www.ebay.com/itm/09-12-VW-GOL...0e57d9&vxp=mtr

or a spoiler that curves up like osir http://www.osirusa.com/mm5/merchant....ry_Code=VGTIEB

i watch the wrc. and all the cars have that giant wings that lets air go through ...

Type in the search box here " one lap America" look for the H2sport car pic's of there rear pwing for the gti they had great success with it. Dam my BB won't let me type in the search box lol.

[the bruce]

Originally Posted by LOUCFUR

heres a question for you guys. (and it doesnt mean i to do it). just wondering what design would give more downforce in the rear.

would a solid rear spoiler be more effective than one that lets air go through?

heres some examples :

solid http://www.ebay.com/itm/10-VW-MK-6-V...cb016c&vxp=mtr

not solid http://www.ebay.com/itm/09-12-VW-GOL...0e57d9&vxp=mtr

or a spoiler that curves up like osir http://www.osirusa.com/mm5/merchant....ry_Code=VGTIEB

i watch the wrc. and all the cars have that giant wings that lets air go through ...

A real wing will provide more downforce if properly designed.
That's why #2 may work better if it is also designed properly. Sadly we can't watch the underside.

I'm sure anile_eight is able to tell us more.

[technologic]

do you guys have a part num for: RS3/TT-RS element?

[the bruce]

vent 8P0 863 149 A and 150A 13,25€
dust shield 8J0 615 311 E and 312E 23,15€ (for 370 mm rotors)
bolt 2x N104 222 03
nut 2x N 907 611 02
tube 2x 8J0 864 133 A

[LOUCFUR]

Originally Posted by the bruce

Sadly we can't watch the underside.

check the 2 pics on the right ...

[LOUCFUR]

Originally Posted by RRacerguy717

Type in the search box here " one lap America" look for the H2sport car pic's of there rear pwing for the gti they had great success with it. Dam my BB won't let me type in the search box lol.

its kool they had success with the car. but the wing looks like shit ...