who has more down-force - LMP1 or F1?

[tuj]

Someone told me that LMP1 cars generate more down-force than an F1 car. I am finding this hard to believe. Anyone know for sure? I was also told that LMP1 cars run a higher ride height at the front than the back???

[mep]

This might answer your question:
http://www.mulsannescorner.com/newsnov10.html
Well not completely because you still don't have the F1 data .

[tuj]

Yeah I found these two links, one an LMP car and one a Champ car:

http://www.mulsannescorner.com/aerodata ... b0300.html
http://www.mulsannescorner.com/aerodata ... lmp00.html

a Champ car at Le Mans in 2003 made 5400lbs of down-force at 200mph. The comparable Panoz LMP1 car made 4266lbs at the same speed, same track.

I also can't figure out why they would run a higher static ride height in front?? It seems to me like you would want front to rear rake to maximize the rear diffuser performance. Also the front ride height being lowered corresponds to higher top speeds as well, which is obviously critical at Le Mans.

[Tim.Wright]

I believe LMP cars have more downforce because their body shape is simply better for downforce creation than an F1 car. This is thanks to the rules rather than the skills of the relative designers.

LMP cars have a massive underfloor area and faired in wheels. F1 cars are stuck with the wheels out in the open for no reason other than tradition and it basically stuffs up whole aerodynamics of the car.

[tuj]

wow interesting. Do you know anything about the ride height being raised in front to try to 'feed' the front diffuser? That seems contrary to NASCAR (which I know is a world of difference) where they try to get the splitter kissing the pavement.

How about DF/kg? An F1 car has to win there, no?

[flynfrog]

I believe LMP cars have more downforce because their body shape is simply better for downforce creation than an F1 car. This is thanks to the rules rather than the skills of the relative designers.

LMP cars have a massive underfloor area and faired in wheels. F1 cars are stuck with the wheels out in the open for no reason other than tradition and it basically stuffs up whole aerodynamics of the car.

The answer is what one has more power less weight. More power less weight the more wing you can slap on the car without the drag be detrementail to lap time.

I would argue that an LMP1 car may not have more df but I would be it has a higher LD ratio becasue of the faired wheels shape ect.

[tuj]

I totally agree that a LMP car should be more efficient at generating df due to the floor design and covered wheels. But I'm just surprised that without a front wing, those LMP cars are getting enough front downforce.

[wesley123]

I totally agree that a LMP car should be more efficient at generating df due to the floor design and covered wheels. But I'm just surprised that without a front wing, those LMP cars are getting enough front downforce.

How so? The LMP's got possibilities to enormous front diffusers, much larger than F1 front wings, front downforce is at such a point that it requires a more forward weight distribution and larger tires at the front. I believe last year Audi ran wider tires at the front than at the rear.

But I'm quite sure an LMP has more downforce, although a large problem would be drag. An F1 car has much less weight and more power to overcome it's drag than an LMP does.

[Lycoming]

F1 cars don't have very effective front wings. Since 2009, the front wing has been absolutely tiny. Though, starting next year, LMP1 cars will be allowed front wings for downforce level adjustment.

I believe last year Audi ran wider tires at the front than at the rear.

Nope. front tires are very slightly narrower than the rear, but almost the same size. Nowhere near the size difference that you see front to rear on an F1 car. This is a relatively recent trend which I believe HPD started with the ARX-02.

How about DF/kg? An F1 car has to win there, no?

probably, since they have about a 200 kilo weight advantage and pull more Gs in corners, though maybe not with the Monza aero package, which is a more direct comparison.

Also, you may find this page for the Bentley EXP Speed 8 interesting, since this car did win le mans and is a bit closer to the champ car chronologically.

http://www.mulsannescorner.com/aerodata ... gtp01.html

[flynfrog]

also if we are going simply to LMP1 prepped for Le Mans they are probably running the bare minimum of DF to keep the drag down for the massive strait.

[wesley123]

I believe last year Audi ran wider tires at the front than at the rear.

Nope. front tires are very slightly narrower than the rear, but almost the same size. Nowhere near the size difference that you see front to rear on an F1 car. This is a relatively recent trend which I believe HPD started with the ARX-02.

Checked it and you're right, the Audi sport technical page states " front: 360/710-18; rear: 370/710-18". Although it would somewhat make sense to run even wider front tires, with the Electric system driving the front wheels plus the aero load there is a large shift in balance forwards.

[tuj]

wow well I guess you learn something new every day. I had no idea the front end of the LMP car was so good at df. I guess you see that 'relatively' big front wing hanging out there on the F1 car and its quite obvious what its doing, whereas I know a lot of the work on the LMP cars goes into the dive planes and louvers.

Any ideas on the ride-height note, ie. LMP car running a higher ride height in front? That just seems counter-intuitive to me, but maybe I've watched too many hours of the RB9 chassis and its very rakish setup.

[Lycoming]

Although it would somewhat make sense to run even wider front tires, with the Electric system driving the front wheels plus the aero load there is a large shift in balance forwards.

Generally speaking, the size of the tires corresponds to the vertical loading on them. The original idea was to shift weight distribution (and downforce distribution) forwards to nearly 50/50 and then use the rear tires on the front as well for a 7% increase in contact patch area.

But, I consider it generally preferable to run a rear biased weight distribution. The front wheel drive doesn't kick in until you're power limited anyways, so adding grip there doesn't really help in that regard. More rear biased will give you better traction on exit up until downforce kicks in and you become power limited, and it will give you better braking performance.

Also, even if your weight distribution is 50/50, your aero balance will be slightly more rear biased. I doubt you would want bigger tires in the front. I also suspect that would be prone to oversteer to do so, but don't quote me on that.

also if we are going simply to LMP1 prepped for Le Mans they are probably running the bare minimum of DF to keep the drag down for the massive strait.

True, but they'll still have quite a lot of downforce; you need it for dunlop curves, porsche curves, tertre rouge and the 3 braking zones on the mulsanne.

wow well I guess you learn something new every day. I had no idea the front end of the LMP car was so good at df. I guess you see that 'relatively' big front wing hanging out there on the F1 car and its quite obvious what its doing, whereas I know a lot of the work on the LMP cars goes into the dive planes and louvers.

Any ideas on the ride-height note, ie. LMP car running a higher ride height in front? That just seems counter-intuitive to me, but maybe I've watched too many hours of the RB9 chassis and its very rakish setup.

Ever had a good look at the front diffuser on an LMP car? There's a lot more at work there than dive planes and louvers. Not sure about the rake thing. I thought they ran nose down, though not to the same extreme as red bull. Then again, I haven't looked all that closely. Where did you read that they ran nose up?

[wesley123]

Although it would somewhat make sense to run even wider front tires, with the Electric system driving the front wheels plus the aero load there is a large shift in balance forwards.

Generally speaking, the size of the tires corresponds to the vertical loading on them. The original idea was to shift weight distribution (and downforce distribution) forwards to nearly 50/50 and then use the rear tires on the front as well for a 7% increase in contact patch area.

But, I consider it generally preferable to run a rear biased weight distribution. The front wheel drive doesn't kick in until you're power limited anyways, so adding grip there doesn't really help in that regard. More rear biased will give you better traction on exit up until downforce kicks in and you become power limited, and it will give you better braking performance.

Also, even if your weight distribution is 50/50, your aero balance will be slightly more rear biased. I doubt you would want bigger tires in the front. I also suspect that would be prone to oversteer to do so, but don't quote me on that.

Agreed. Although the R15 showed quite well that Front downforce is much easier found than rear downforce. The R15 pretty much ran a front wing, and the R15+ and later version ran the legality panels in such a way that they can be considered a front wing flap.

This would make a more forward CoP preferable in some way, and afaik the front wheel drive electronic system isn't speed limited anymore, making it an interesting way to go.

wow well I guess you learn something new every day. I had no idea the front end of the LMP car was so good at df. I guess you see that 'relatively' big front wing hanging out there on the F1 car and its quite obvious what its doing, whereas I know a lot of the work on the LMP cars goes into the dive planes and louvers.

Any ideas on the ride-height note, ie. LMP car running a higher ride height in front? That just seems counter-intuitive to me, but maybe I've watched too many hours of the RB9 chassis and its very rakish setup.

Ever had a good look at the front diffuser on an LMP car? There's a lot more at work there than dive planes and louvers. Not sure about the rake thing. I thought they ran nose down, though not to the same extreme as red bull. Then again, I haven't looked all that closely. Where did you read that they ran nose up?[/quote]

The R15 ran nose up at Le Mans 2009 because of it's amount of front grip which would destroy their tires. That was the only time I ever read of them doing so and i have huge doubts of that actually happening.

[Juzh]

I read somehwere years ago that RB6 was supposed to develop somewhere in the region of 4500 lbs at 160mph. Really can't say where. Might be some racing magazine.