How much actual downforce from spoiler and side skirts at 80 mph?

Rando · 12-07-2008, 07:56 PM

I know they help to some minuscule extent... just curious as to what that number is, in terms of number of g's.

I figure someone might know, even though it's a tricky question. Google didn't give much hope.

Thanks!

gtrokin330 · 12-07-2008, 08:04 PM

i believe those m3 lips give the most...something like 45+ rwhp

McLuVan · 12-07-2008, 08:05 PM

depends on speed

Rando · 12-07-2008, 08:16 PM

Yes, that is why I specified 80 mph in the thread subject.

Just want to get some rough idea either as an absolute number (like 0.05g) or on absolute terms as a % of overall grip.

noro · 12-07-2008, 08:22 PM

Sideskits = 0.

Rear spoiler close to 0. The rear spoiler at best normalized the turbulence in the rear of the car which can be beneficial in terms of reducing drag. To get real down force you need a rear wing and a front lip.

Rando · 12-07-2008, 08:48 PM

ok, how about front lip then? any rough idea?

Thanks

bimmerFUD · 12-07-2008, 09:29 PM

Quote:

Originally Posted by Rando

Just want to get some rough idea either as an absolute number (like 0.05g) or on absolute terms as a % of overall grip.

If it was as much as 0.05g, they'd be stupid not to advertise the number. But I'd be surprised if there's any difference.

Good question, though.

josephr25 · 12-07-2008, 10:03 PM

You would need a 3D model and a CFD program like Fluent to get some sort of measurement, and quite possibly wind tunnel data to correlate computer data and controlled real-life data.

You can model the stock parts, then modified parts, to see if there are actual gains/losses w/ design change. Bare in mind that this doesn't include flow with the actual car. Then you have to ask yourself if even if there are gains, does it make the car any faster.

So to answer your question, I would say the gain is not discernable. Keep in mind that drag increases a lot more than lift as speed increases

JunkStory · 12-08-2008, 02:32 AM

I wouldn't worry about it unless you travel on the Autobahn @ 150mph to work everyday.

Year's_End · 12-08-2008, 02:38 AM

Quote:

Originally Posted by noro

Sideskits = 0.

Rear spoiler close to 0. The rear spoiler at best normalized the turbulence in the rear of the car which can be beneficial in terms of reducing drag. To get real down force you need a rear wing and a front lip.

+1

the amount of downforce they make is negligible.

wj4 · 12-08-2008, 02:39 AM

At 80 MPH, you're not going to feel anything and I'm sure the difference will be minimal. You need to have a big grotesque wing like the Evo and be in the triple digit zone before you start to feel something IMO.

E90330iS · 12-08-2008, 02:45 AM

Quote:

Originally Posted by wj4

At 80 MPH, you're not going to feel anything and I'm sure the difference will be minimal. You need to have a big grotesque wing like the Evo and be in the triple digit zone before you start to feel something IMO.

true. and it if u felt anything its stability not speed

Psylight · 12-08-2008, 10:43 AM

Double decker sushi table rear wing is needed.

Nikolas · 12-08-2008, 10:47 AM

At 80 you will get absolutely no benefit.

kingflys · 12-08-2008, 11:48 AM

Taking it up to 88 should kick in the flex capacitor though

toughluck · 12-08-2008, 12:00 PM

Quote:

Originally Posted by kingflys

Taking it up to 88 should kick in the flex capacitor though

nice. +1

dth656 · 12-08-2008, 12:39 PM

i may be wrong, since its been many years since i've taken fluid mechanics, but i think that you'd have to be going 110-115+ plus to realize any kind of benefit from an aero pkg. anyone remember the relevant equations?

Year's_End · 12-08-2008, 01:57 PM

http://www.autoanything.com/body-kits/51A23.aspx

Rando · 12-08-2008, 11:32 PM

Cool, thanks for the link. No numbers, unfortunately, but they are very honest about what they're selling! Always nice to see that.

I also forgot to mention one more silly thing... presumably if you put your moonroof to "tilt" you get a tad more downforce too. Heh... But obviously not a ton, because then the tilt mechanism would break!

gos · 12-08-2008, 11:37 PM

Quote:

Originally Posted by toughluck

nice. +1

Flux capacitor, not flex. -1

Quasimodem · 12-09-2008, 01:29 AM

It's not the plane, it's the pilot.

Strongmad · 12-10-2008, 01:53 PM

Quote:

Originally Posted by Kampfer

You would need a 3D model and a CFD program like Fluent to get some sort of measurement, and quite possibly wind tunnel data to correlate computer data and controlled real-life data.

You can model the stock parts, then modified parts, to see if there are actual gains/losses w/ design change. Bare in mind that this doesn't include flow with the actual car. Then you have to ask yourself if even if there are gains, does it make the car any faster.

So to answer your question, I would say the gain is not discernable. Keep in mind that drag increases a lot more than lift as speed increases

Because we all know what CFD stands for,
Completely Fabricated Data
Colors For Dollars?
Can't Find my Data?

12-07-2008, 07:56 PM	#1
Rando Lieutenant 52 Rep 487 Posts Drives: BMW Join Date: Mar 2007 Location: CA iTrader: (0)	How much actual downforce from spoiler and side skirts at 80 mph? I know they help to some minuscule extent... just curious as to what that number is, in terms of number of g's. I figure someone might know, even though it's a tricky question. Google didn't give much hope. Thanks!
	Appreciate 0 Tweet Quote

12-07-2008, 08:04 PM	#2
gtrokin330 Brigadier General 150 Rep 3,865 Posts Drives: TT Join Date: Sep 2007 Location: LI iTrader: (7)	i believe those m3 lips give the most...something like 45+ rwhp
	Appreciate 0 Quote

12-07-2008, 08:05 PM	#3
McLuVan Lieutenant General 304 Rep 13,114 Posts Drives: ///M3 Join Date: Jan 2008 Location: Socal~818~ iTrader: (1)	depends on speed __________________
	Appreciate 0 Quote

12-07-2008, 08:16 PM	#4
Rando Lieutenant 52 Rep 487 Posts Drives: BMW Join Date: Mar 2007 Location: CA iTrader: (0)	Yes, that is why I specified 80 mph in the thread subject. Just want to get some rough idea either as an absolute number (like 0.05g) or on absolute terms as a % of overall grip.
	Appreciate 0 Quote

12-07-2008, 08:22 PM	#5
noro Colonel 90 Rep 2,707 Posts Drives: '91 M3, '04 E46 ZHP, '72 2002 Join Date: Aug 2006 Location: Boston iTrader: (0)	Sideskits = 0. Rear spoiler close to 0. The rear spoiler at best normalized the turbulence in the rear of the car which can be beneficial in terms of reducing drag. To get real down force you need a rear wing and a front lip. __________________ zhpregistry.net - ZHP stats and free classifieds.
	Appreciate 0 Quote

12-07-2008, 08:48 PM	#6
Rando Lieutenant 52 Rep 487 Posts Drives: BMW Join Date: Mar 2007 Location: CA iTrader: (0)	ok, how about front lip then? any rough idea? Thanks
	Appreciate 0 Quote

12-07-2008, 10:03 PM	#8
josephr25 Major 68 Rep 1,456 Posts Drives: 2008 E92 335i Join Date: Aug 2008 Location: Irvine, CA iTrader: (2) Garage List 2008 BMW 335i Coupe [0.00]	You would need a 3D model and a CFD program like Fluent to get some sort of measurement, and quite possibly wind tunnel data to correlate computer data and controlled real-life data. You can model the stock parts, then modified parts, to see if there are actual gains/losses w/ design change. Bare in mind that this doesn't include flow with the actual car. Then you have to ask yourself if even if there are gains, does it make the car any faster. So to answer your question, I would say the gain is not discernable. Keep in mind that drag increases a lot more than lift as speed increases
	Appreciate 0 Quote

12-08-2008, 02:32 AM	#9
JunkStory Major 160 Rep 1,307 Posts Drives: E92 M3, 8V RS3 Join Date: May 2008 Location: 98230 iTrader: (3)	I wouldn't worry about it unless you travel on the Autobahn @ 150mph to work everyday.
	Appreciate 0 Quote

12-08-2008, 02:39 AM	#11
wj4 Major General 335 Rep 7,719 Posts Drives: E90 manual 335i Join Date: Nov 2006 Location: Burbank, CA iTrader: (8)	At 80 MPH, you're not going to feel anything and I'm sure the difference will be minimal. You need to have a big grotesque wing like the Evo and be in the triple digit zone before you start to feel something IMO.
	Appreciate 0 Quote

12-08-2008, 10:43 AM	#13
Psylight Brigadier General 92 Rep 3,488 Posts Drives: Teh Space Gray E92 M 6MT Join Date: Nov 2007 Location: Diamond Bar ,California iTrader: (11)	Double decker sushi table rear wing is needed. __________________
	Appreciate 0 Quote

12-08-2008, 10:47 AM	#14
Nikolas Colonel 313 Rep 2,576 Posts Drives: 996 TT Join Date: Jul 2007 Location: Sierra Mountains iTrader: (0)	At 80 you will get absolutely no benefit.
	Appreciate 0 Quote

12-08-2008, 11:48 AM	#15
kingflys Kingflys 8 Rep 53 Posts Drives: 2007 E90 328i Join Date: Nov 2008 Location: Riverside, CA iTrader: (1)	Taking it up to 88 should kick in the flex capacitor though
	Appreciate 0 Quote

12-08-2008, 12:39 PM	#17
dth656 First Lieutenant 36 Rep 394 Posts Drives: e90 330i Join Date: Dec 2006 Location: ASCII iTrader: (0)	i may be wrong, since its been many years since i've taken fluid mechanics, but i think that you'd have to be going 110-115+ plus to realize any kind of benefit from an aero pkg. anyone remember the relevant equations? __________________ go bears
	Appreciate 0 Quote

12-08-2008, 01:57 PM	#18
Year's_End Lieutenant General 1138 Rep 12,444 Posts Drives: 2020 Shelby GT350 Join Date: Feb 2007 Location: FL iTrader: (0)	http://www.autoanything.com/body-kits/51A23.aspx __________________ Past: '08 E92 335i\|ZPP\|ZSP\|6AT Past: '15 Mustang GT\|401A\|PP\|6MT Current: '20 Shelby GT350\|6MT
	Appreciate 0 Quote

12-08-2008, 11:32 PM	#19
Rando Lieutenant 52 Rep 487 Posts Drives: BMW Join Date: Mar 2007 Location: CA iTrader: (0)	Cool, thanks for the link. No numbers, unfortunately, but they are very honest about what they're selling! Always nice to see that. I also forgot to mention one more silly thing... presumably if you put your moonroof to "tilt" you get a tad more downforce too. Heh... But obviously not a ton, because then the tilt mechanism would break!
	Appreciate 0 Quote

12-09-2008, 01:29 AM	#21
Quasimodem Colonel 147 Rep 2,383 Posts Drives: 335d Join Date: Oct 2008 Location: California iTrader: (0) Garage List 2009 335d US [0.00]	It's not the plane, it's the pilot.
	Appreciate 0 Quote