Downforce - how much?

[xpensive]

You're a good citizen, marcush.

[marcush.]

I could not resist ...makes me surely a favorite choice as Blockwart in 2010,I guess..

[Formula None]

Good resource:

http://www.mulsannescorner.com/data.html

2001 Bentley EXP Speed 8 LMGTP

High downforce configuration:

Downforce:
3094 lbs. @ 150 mph
4455 lbs. @ 180 mph
5500 lbs. @ 200 mph

Low downforce configuration:

Downforce:
2022 lbs. @ 150 mph, with 546 lbs. of drag
2911 lbs. @ 180 mph, with 787 lbs. of drag
3594 lbs. @ 200 mph, with 971 lbs. of drag

Lift-to-drag ratio: 3.70:1
Coefficient of drag: .5038
Coefficient of lift: -1.87
Reference area: 1.75 meters square

2011 Dome S102i

Le Mans setup (i.e. low downforce):

Map average:

Downforce:
2737 lbs. @ 150 mph, with 666 lbs. of drag
3941 lbs. @ 180 mph, with 960 lbs. of drag
4865 lbs. @ 200 mph, with 1185 lbs. drag.

Lift-to-drag ratio: 4.10:1
Map average balance: 45.50%

Developed but not raced. Reflects the effects of the 2009-2011 regulations (narrow span and chord rear wing, domed skid ['09], rear fender regulations ['10], and big-honking-fin ['11])

IMSA & Group C were known for having the highest amounts of downforce ever. Must have had amazing tires in those days (anyone have any info?):

1991-1993 Toyota Eagle MkIII GTP


Image copyright Mark Windecker Debut variant:

Downforce:
3802 lbs. @ 150 mph, with 929 lbs. of drag
5476 lbs. @ 180 mph, with 1338 lbs. of drag
6760 lbs. @ 200 mph, with 1652 lbs. of drag

Lift-to-drag ratio: 4.09:1
Image copyright John Brooks Twin-tiered Bi-plane rear wing development, max downforce:

Downforce:
5217 lbs. @ 150 mph, with 1180 lbs. of drag
7513 lbs. @ 180 mph, with 1699 lbs. of drag
9275 lbs. @ 200 mph, with 2097 lbs. of drag

Lift-to-drag ratio: 4.42:1
Image copyright Greg Cooper Daytona configuration:

Downforce:
3617 lbs. @ 150 mph, with 723 lbs. of drag
5209 lbs. @ 180 mph, with 1042 lbs. of drag
6431 lbs. @ 200 mph, with 1286 lbs. of drag

Lift-to-drag ratio: 5.00:1

Open wheel:

2001 Penske-Reynard-Honda 01I


A Road track configuration:

Downforce:
2750 lbs. @ 150 mph, with 924 lbs. of drag
3961 lbs. @ 180 mph, with 1331 lbs. of drag
4888 lbs. @ 200 mph, with 1644 lbs. of drag

Lift-to-drag ratio: 2.97:1
A Short oval configuration:

Downforce:
1675 lbs. @ 150 mph, with 725 lbs. of drag
2412 lbs. @ 180 mph, with 1043 lbs. of drag
2978 lbs. @ 200 mph, with 1289 lbs. of drag

Lift-to-drag ratio: 2.31:1
A Super-speedway configuration:

Downforce:
1000 lbs. @ 230 mph, with 950 lbs. of drag

Lift-to-drag ratio: 1.05:1

[wesley123]

because of those articles i think 12000N is a bit over the top.

Thereby, the lmp's do not got more downforce imo then open wheelers, their downforce is just more efficient, thus reaching a higher L/D

[DaveW]

Aero numbers are, without detailed configuration specs., indicative, rather than definitive. However, with apologies, I can't conclude from your numbers, wesley, that open wheelers make as much downforce as good LMP vehicles (& the Bentleys were good aero examples, I believe, as were the Reynard CHAMP cars). I am comfortable with your L/D statement, however.

[ringo]

because of those articles i think 12000N is a bit over the top.

Thereby, the lmp's do not got more downforce imo then open wheelers, their downforce is just more efficient, thus reaching a higher L/D

it is very possible that they do get more downforce.
If you compare the size of an LMP you could see why it's possible.

It probably makes less downforce per kg of car, or less per square inch, but i think a 2m wide car has enough floor, wing, front and rear diffuser area to surpass an F1 in raw downforce numbers. Also close wheel cars have less lift at the wheels as well, and you can see why it can be better.

Assuming it can reach the designated speed at the highest downforce setting it will see those 5000lb numbers.

[Jersey Tom]

IMSA & Group C were known for having the highest amounts of downforce ever. Must have had amazing tires in those days (anyone have any info?):

Amazing in what regard?

[Ogami musashi]

As said by mike@ mulsannescorner those figures are theoritical in that they follow the square of speed curve; The high speed (200mph) data is calculated from the lower speed experimental data.

thus, they don't take into account all mechanical effect related variations of downforce and drag with speed;

the actual figures are far lower and in many case, again as stated by the owner of MC, the 200 mph are purely speculative since the drag is far greater than power available.

[marekk]

because of those articles i think 12000N is a bit over the top.

Thereby, the lmp's do not got more downforce imo then open wheelers, their downforce is just more efficient, thus reaching a higher L/D

As the engine power and top speed (which means top drag) of LMP anf F1 cars are roughly the same, and L/D for LMP is WAY better then for open wheelers, downforce has to be much bigger - could be 1,5 to 2 times IMO.

[Ogami musashi]

Not way better;

Recent F1 cars ratios are about 4. And current lmp are about the same. Older GroupC cars had 5 to 6.

[PlatinumZealot]

My guess is the LMP's are more, I don't see what is so special on the F1 car that would give it more. LMP :- bigger wings, bigger floor, bigger rear diffuser, fenders, front diffuser etc.

[Ogami musashi]

I don't quote numbers out of my hat...those are numbers going on in the pitlane.


the "bigger" you quote is not relevant, the lmp cars are heavier and the bigger is often wider but not more surface; In addition many solution are far less aggressive than in F1 because the aero rules are far more constrained in current lmp (yes..they can't add bits everywhere just to have clean airflow), in 2008 the F1 cars had monstruous L/D ratios (for an open wheeler of course) topping at 4,5 due to all the winglets.

Use of vortex lift, flexibility of wings and well as blown solutions are reasons why F1 ratios are far more important than other open wheelers, and if F1 cars had real venturis...windtunnel tests show possible ratio of 7.

[shelly]

agree with ogami
efficency around 4, front wing Scz 1.2 to 1.5, front wing load 500 to 700 kg @300kph

[Formula None]

IMSA & Group C were known for having the highest amounts of downforce ever. Must have had amazing tires in those days (anyone have any info?):

Amazing in what regard?

Heavier car (relative to our open wheel friends, 800kg vs ~600kg)with potentially more downforce... Maybe they were constructed exactly the same way regardless, I don't know, that's why I was asking.

[Jersey Tom]

I'd wager currently stock cars probably put as much or more load on smaller tires

Certainly a unique challenge though, designing around the RANGE of load, from peanuts to tons.