5,000lbs?

davehenrie · 22 Mar 2009, 05:49 (Ref:2421804)

During the SpeedTV broadcast of Sebring, they tried to explain why the new Acura P1 cars needed hydraulic power-steering. Dorsey Schrader said it would be similar to we listeners placing 5,000lbs on the nose of our car.

Does this suggest the ARX02a produces 5,000lbs of Downforce? Or the combination of downforce and high friction from the wide tires is similar to the weight of 5,000lbs.

Or was he just throwing out a number to impress us?

dh

sssssssss · 22 Mar 2009, 17:54 (Ref:2422114)

From what I've noticed so far, commentaries are quite general when it comes to numbers... My take is that your last possible answer is the truest!

Kind of on-topic too: I remember people guessing around 10,000 lbs for the '92-'93 Peugeot 905, which was the very fastest sportscar ever made in terms of cornering speed/overall lap times, that is, until last year's Peugeot 908, which is quite similar in cornering efficiency and lap times to the 905. And I think 10,000 is quite plausible and valid for the 908 and R15 as well.

crazy · 23 Mar 2009, 07:32 (Ref:2422461)

Downforce is dependant on speed (among others) so that number doesn't mean anything.

sssssssss · 23 Mar 2009, 08:06 (Ref:2422481)

Looking on mulsannescorner.com at the aerodynamics database, I kind of figured out that if speed isn't mentioned, it usually means you're talking about downforce at the highest speed the prototype will travel on a regular track, which is about 200 mph (ca. 320 km/h). But then of course, downforce is dramatically variable from one setup to another, so from track to track etc.

My guess is that Sebring is a high downforce track, because it has a lot of turns, some of them being pretty tight, the track is notoriously bumpy and unstable and also, looking at the top speeds not even touching 300 km/h on a straight as long as the Ullmann straight, the cars must have tons of downforce on them.

protopuma · 23 Mar 2009, 08:31 (Ref:2422500)

I doubt they are even close to 10,000. Group C and GTP cars had full tunnels and twin-tier rear wings to create that much. The current cars have none of that.

davehenrie · 23 Mar 2009, 13:49 (Ref:2422757)

I went over Mikes data as well, the newest cars in his list are the 01 Bentley and 03 Lister. While those cars are similar in design to current cars, even the 2008 cars are different because of the raised minimum ride height. Add to that the smaller rear wing mandated for 2009 and you should be seeing some reduction

Those two cars, at 200mph put out 5500lbs for the Bentley and 4622lbs for the Lister.

I would assume the mechanical grip of the tires to be greater now, especially compared to the Bentley which had to race on narrower tires than the LMP1 cars of that era. But I wouldn't think, even with the two new cars this year, that they have doubled the downforce of the Bentley.

sssssssss · 23 Mar 2009, 14:06 (Ref:2422770)

The Peugeot had tremendous downforce last year. To be honest, I can't really understand where it all came from with the increased minimum ride height etc., but the numbers are quite obvious: 3:18 qualifying lap for the '08 908 with (as far as we know so far) 345 km/h top speed on the Mulsanne vs. 3:21 qualifying lap for the '92 905 with 351 km/h top speed on the Mulsanne. If we consider that the new Tetre Rouge made the lap about 3.5 to 4 seconds shorter and the top speed about 10 km/h higher for the fastest prototypes, the '92 905 and the '08 908 really seem very similar in track efficiency - in fact, even with a lower top speed, the 908 gets the same timing as the 905.
True, we don't know if the 905 really had around 10,000 lbs of downforce, but if it did, clearly the 908 has them too, from last year on.
The Bentley on mulsannecorner.com is the EXP Speed 8, so the 2001-2002 car, not the 2003 Speed 8 which won Le Mans that year, and it didn't necessarily excel in downforce as far as track data can reveal: 3:35.056 qualifying lap in the very fast 2002 race (when the Audi R8 did 3:29 and bettered the '99 Toyota GT-One) with a top speed of 336 km/h if I remember correctly. Even on the current track layout, that would have been around 3:31 with ca. 345 km/h top speed - so the top speed was quite the same as last year's Peugeot 908 and the lap was about 13 seconds slower. That should give us a picture about how much downforce the '08 908 really had. And take 260 km/h in the Porsche curves as another example.

davehenrie · 26 Mar 2009, 02:36 (Ref:2424954)

Quote:

Originally Posted by sssssssss

The Peugeot had tremendous downforce last year. To be honest, I can't really understand where it all came from with the increased minimum ride height etc., but the numbers are quite obvious: 3:18 qualifying lap for the '08 908 with (as far as we know so far) 345 km/h top speed on the Mulsanne vs. 3:21 qualifying lap for the '92 905 with 351 km/h top speed on the Mulsanne. If we consider that the new Tetre Rouge made the lap about 3.5 to 4 seconds shorter and the top speed about 10 km/h higher for the fastest prototypes, the '92 905 and the '08 908 really seem very similar in track efficiency - in fact, even with a lower top speed, the 908 gets the same timing as the 905.
True, we don't know if the 905 really had around 10,000 lbs of downforce, but if it did, clearly the 908 has them too, from last year on.
The Bentley on mulsannecorner.com is the EXP Speed 8, so the 2001-2002 car, not the 2003 Speed 8 which won Le Mans that year, and it didn't necessarily excel in downforce as far as track data can reveal: 3:35.056 qualifying lap in the very fast 2002 race (when the Audi R8 did 3:29 and bettered the '99 Toyota GT-One) with a top speed of 336 km/h if I remember correctly. Even on the current track layout, that would have been around 3:31 with ca. 345 km/h top speed - so the top speed was quite the same as last year's Peugeot 908 and the lap was about 13 seconds slower. That should give us a picture about how much downforce the '08 908 really had. And take 260 km/h in the Porsche curves as another example.

Going from 200mph, which is the highest postest number at MM's site, and the 208mph which is what I hope the top speed was last year, the difference in added downforce according to a sim utility I have is just over 8%.( don't know if it's accurate, I plugged in the two numbers and noted the difference.) That would increase the top df for the Bentley from 5500lbs to 5948lbs. An impressive gain just based on mph. So that is still only just shy of 6000lbs with the wider wing, lower ride height but narrower tires. Do we really think there is another 4000lbs of DF on the 908? I have to give some of that cornering to the tires. But again, can't say just how much. Drag has got to figured in there too, adding 4000lbs of df would be akin to around 1000lbs or so more drag. (guesstimating a 3+:1 lift to drag ratio.)

sssssssss · 26 Mar 2009, 12:02 (Ref:2425197)

I personally find it plausible that last year's 908 had much more lbs than the Bentley EXP Speed 8, considering the track data that I've posted previously. It might have to do with tires as well, that the Peugeot cornered that quickly, but keep in mind that Audi and Peugeot had exactly the same tire choice and while the 908 did 3:18s, the mighty R10 did 3:23. From the getgo in 2006, the R10 was considerably faster and had more downforce than the Bentley EXP Speed 8 and still, in its last phase of deveopment - 2008 - it was 5 full seconds slower than the Peugeot 908, with comparable top speed.
And again, also comparing the 908 with the 905, they are very very similar in track data - and with the 905 having a small advantage in top speed, I'd say the 908 has a slight advantage in downforce even over the 905. But again, the question is if the 905 really had around 10000 lbs... in track data terms, when comparing it to the Bentley for instance, it may look plausible to me.

davehenrie · 26 Mar 2009, 18:59 (Ref:2425464)

Quote:

Originally Posted by sssssssss

I'd say the 908 has a slight advantage in downforce even over the 905. But again, the question is if the 905 really had around 10000 lbs... in track data terms, when comparing it to the Bentley for instance, it may look plausible to me.

Fascinating stuff. I appreciate your insight and information
thanks

sssssssss · 26 Mar 2009, 19:46 (Ref:2425492)

You could choose one single word to quote and comment about how fascinating it was and your post would be just as valuable. If you didn't find any relevance in that part, here it is: I'm no specialist and I generally don't speak in absolute terms, that's why you'll find lots of "I" in my messages

. But let's avoid getting this discussion nowhere. If I repeated myself pretty much with the last post, it's just because it seemed to me that the answer to the previous wasn't really considering what I've written in it.

JAG · 26 Mar 2009, 21:35 (Ref:2425570)

I don't think you can compare the 908 and 905, very different cars and 15 years apart.

What the 908 loses in ultimate downforce(which wouldn't be used at Le Mans) it makes up for in the chassis, brakes, tryes etc.

As for comparisons with the Bentley, again it's 4-5 years older, and wasn't subject to such intense competition which drives the pace forward 3-4 seconds per year at Le Mans given the same regs.