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Mulsanne's Corner

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Le Mans 2011


All news content copyright Michael J. Fuller, unless otherwise noted

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>>Race Car Engineering Magazine's 24 Hours of Le Mans coverage<<
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>>2011 24 Hours of Le Mans entry list<<
>>Andy Blackmore's Le Mans 2011 Spotter's Guide<<
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>>Baekdal, Live Le Mans Tracker<<

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Audi R18, Mike Rockenfeller accident, Le Mans 20116.14.11

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This is what's left of Mike Rockenfeller's Audi R18 following his accident on the strip from Mulsanne to Indianapolis.  Considering the severity of this accident, along with that of Alan McNish's, as much as we bang on the ACO about what they get wrong (we do it because we love you), this is something the ACO have gotten right.  The regulations behind today's modern LMP monocoque produce a safety structure that is extraordinarily strong.

We also wanted to point out that both accidents showed how effective the big honking fin is.  Yes, we hate the looks but admittedly they are growing on us (remember how ridiculous we thought the narrow rear wings were?  Yeah, barely notice them now.  We're fickle.  Sorry.)  Rockenfeller's accident was the truer test in that his car pitched into a sudden and unintended yaw at a speed exceeding 300 km/h.  The car clearly stayed glued to the track, but unfortunately it made contact with a Armco barrier.  As bad as it sounds, that must have been the optimal outcome and much preferred over the car taking flight and clearing the Armco heading for the trees.  

6.11.11

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Sam's been working on figuring out the protagonist's race strategies:  Peugeot is running a lower drag car – this is seen in their better speed trap figures (maximum speeds of 343 km/h to Audi's 334 km/h) and better fuel mileage. Note Peugeot's "anti wicker" wing (below, 6.8.11), it gets around the gurney and cuts drag.  Meanwhile the Audi, which has higher downforce, is better in the twisty bits.  Finally we know from our source in Peugeot Sport that the 908 has a very narrow operating window.  This has a lot to do with the wide fronts.  As the temperature dropped the 908's all lost pace – whilst Audi just motored on.  Simple: come 9 am and the Peugeots will start catching up again.  That is, if there are any Audis to catch up to.

>>Assuming Audi and Peugeot have near about the same horsepower, and that Peugeot have gone low drag (relative), solving for drag in our power estimation formula shows only about a 60 lb difference in drag between the two with Peugeot running to a top speed average of 335.1 km/h while the Audi is averaging 329.6 km/h.  We've calculated these averages from the ACO's data which notes the top 5 top speeds for each car number and are taken from Free Practice and qualifying sessions 1-3.
>>Good morning race fans!  Last night we started trawling through the ACO's session data from the free practice and qualifying 1-3.  For now that data can be found here though will probably be moved and archived after the race.  For now we're compiling average top speeds and taking all the data to construct a LM 2011 average for the cars I'm looking at.  As we were most interested in the Aston Martin given it only really had one timed lap at the Test, I've gone back and redone the calculations for it.  



So we now have the AMR-One producing between 395-400 hp on the low end and 440 or so on the high end.  Figure towards the high end of power assuming high(er) drag though their cornering speeds don't speak to carrying loads of downforce.  It's not like the car shows to be a rocket through the Porsche curves (It's about mid pack compared to the other LMPs for Porsche) for instance or any of the other corners.

Previously we had calculated the AMR-One as having between 465 and 500 hp.  But ultimately that was based on what was effectively a single lap at the test day where the car went through the traps clearly in anger.  Sam spoke to Aston Martin yesterday and they admitted to having "10% less power."  When clarified, they were admitting to being 10% down on their previous output, presumably for longevity.  Compared to our previous estimates, -10% puts our new estimates spot-on or nearly so.
>>Wired magazine takes note of our joint coverage with Race Car Engineering magazine.

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Audi R18, Le Mans 20116.9.11

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Not much out of Sam today:

Last night Audi ran with single and twin dive planes on the cars, swapping nose and engine cover to adjust the car balance. They also fitted the Tire Temperature Monitor System nose seen on test day.  As we mentioned yesterday, Peugeot has been doing this as well and really shows the concentration on optimizing the contact patch of the wide fronts up until the last possible minute.

Peugeot is using the anti-wicker wing on all three cars.

Level 5 posted a nice Le Mans lap in-car video.

Naturally you'd expect us to have something on the Delta Wing announcement but you'll have to wait while we put our thoughts together in a constructive manner.  That is, if we don't get bored and go off and do something else.  Tomorrow perhaps.
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Peugeot 908, Le Mans 20116.8.11

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Sam snapped a picture of Peugeot's answer to Oak Racing's rear wing flap.  Just like Oak Racing's rear wing flap, Peugeot's is designed to reduce the relative angle of the gurney in order to reduce drag.   Peugeot has turned to a slotted flap wing section and as such has a deep slot running along the trailing edge.
Peugeot rear wing flapIn a multi-element wing assembly, the slotted flap bleeds high pressure air into the boundary layer delaying flow separation.  But in this case the height of the slot is simply being used to leverage the gurney backwards.  When the line is connected between the top of the wing and the trailing edge, it results in an angle reduction for the mandatory 20 mm gurney.  There's certain to be an interesting story as to how quickly Peugeot was able to design, test, and get this flap onto the car given all the other things that were going on between the Test and the race.
Peugeot 908, Le Mans 2011Taken today, note the tire temp sensor above the fender.  While it is unusual to run tire temperature sensors in official practice, Peugeot did similar at Spa.
Aston Martin AMR-One, Le Mans 2011The Aston Martin AMR-One has a revised exhaust system.
>>We're told Thursday's LMP announcement involves Highcroft Racing.  The announcement will be made at 10am French time (4am US EST).  It's been pointed out that it was Highcroft who backed away from Honda; had Highcroft found sponsor money they would have continued with HPD.  But that Highcroft is involved with this announcement must signal they are moving forward with another manufacturer.  Not to mention, we've been led to believe it is more than simply a team announcing a new chassis/direction.  What manufacturer you ask?  You're betting we're not going to double down on yesterday's prediction (Hyundai America: 74.212.225.213)...

...did we mention Toyota peaks in too?  Toyota Motorsports: 213.83.46.80 (good morning TMG!),
 but then Toyota's LMP program is the worst kept secret in racing...though you'd like to think Toyota would announce sooner rather than later...yeah, we're hedging our bets.  But if it turns out Highcroft announces something comparatively mundane, like that they're running Audis or something, all bets are off.*

*A few hours later and indeed, all bets are off...Delta Wing?  A controversial open wheel concept becomes the ACO's latest shiny toy?  Things must really be bad for the ALMS to loose their best team to this project.  No offense to Highcroft, Delta Wing, or All American Racing.  

Oh, and we'll stop with the predictions now (we never were very good at that, notice we never make any race predictions?).

WTF Hyundai, why you leave me hanging...so who should I send the bandwidth bill to?  Seriously.

Peugeot 908, Le Mans 20116.7.11

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Sam's notes from today:

I hear from those in the Silver corner that Peugeot has a new rear wing which slopes in an unusual way, negating the impact of the wicker.  It's pretty clear someone's been looking at the Oak Racing rear wing pics on Race Car Engineering & Mulsanne's Corner?

Sam sends along a shot of the Peugeot's turbo installation.
Rebellion Lola Toyota, Le Mans 2011A nice look at the alternative nose configuration of the Lola Toyota, don't think it has run in that trim yet but the covers seem to be on for Le Mans given the alternate nose's high downforce nature.
Aston Martin AMR-One, Le Mans 2011Bit of nature on the Aston Martin – aside from that, looking at the finish of the bodywork, it is not what you would expect – I think the very short development program has hit the AMR-One a bit.  Still, start of a three year program though, the car does have potential.  May also have a revised exhaust exit – or, at least a neater one – will see tomorrow. 
Audi R18, Le Mans 2011Audi R18 front brake ducting
Hyundai to ALMS LMP?  At Le Mans today it came out to expect a "big" announcement on Thursday of a manufacturer backed effort that would have a ALMS centered, USA based, LMP program.  That's all we knew.  Emails back and forth with Sam eliminated Toyota (German based, Japanese money), Mazda (email to John Doonan, Head of Mazda Motorsports North America said, "Honestly, not that I know of...You been reading Murphy the Bear again!?"), Nissan (more likely than other possible Japanese efforts, but all money being spent currently is Japanese based), Ford (close contacts said no), Chrysler (similar to Ford), GM (heavily invested in GT2 Corvette and contacts seemed to put the kibosh on this as well).  Then who?

We've often hinted about it and some times mention it directly, but we track the IP traces of the hosts that hit the Mulsanne's Corner server.  It's a standard procedure, our web hosts collect all sorts of data behind the scenes and most of the time we don't even bother looking at it.  But we take note of the IPs because it's a pretty easy task to pop the numbers into a IP look up and see who they are.  But the problem is that it is a time consuming and manual process; cut, paste, click, ID, next (if anyone knows how to do this as a batch process where you grab 1000s of IP and plug them in contact this office!).  Time and again.  So we only tend to look at the top 25 and only every other month or so.

Back in March of this year, following Sebring, we were going through the IP log...and the top hitters tend to read like: Wirth Research:  217.33.58.2, Prodrive Motorsports Assignment: 77.73.9.130, Honda R&D CO., Ltd: 211.121.174.34, Audi AG, Ingolstadt : 143.164.102.14, etc.  But one stuck out:



Well now...so what are you up to Hyundai?

With today's rumor, Hyundai certainly begins to make a lot of sense.  Back in 2009, a sportscar team based in Atlanta put out feelers for crew to work on a Hyundai backed ALMS GT program that would transition to LMP2 over a 5 year program.  It never panned out in that manner, but at very least it shows desire and direction.

We were also told today that Hyundai has been putting out RFQs for ALMS-centric sportscar programs as recently as the begining of this year...

We checked last month's stats and Hyundai is still visiting...

This is investigative reporting in the face of any hard facts and there are certian to be those that poo-poo our methodology; we admit we have absolutely no direct knowledge of this program.  So we might look pretty silly Thursday and in the end we've sent IT departments at the above companys scrambling to cover their footprints.

If not, welcome to the show Hyundai.

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Audi R18, Spa 20116.6.11

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We've been pondering the Audi images a bit further.  Sometimes you have to take risks and put stuff out there as you ponder on the fly.  Take this image for example.  We can't figure out the function of the very prominent foil covered cooling ducts that route their very intentional way through the engine bay.  The two ducts, one either side of the car, start at the firewall of the monocoque (1), clearly piercing the monocoque, and feed from the tub rewards into the carbon bellhousing (2).  Along the way, cooling flow is siphoned off (3), (4), and (5).  What's the source?  The front nose vent?  Seems a rather tortured route...We hate to be the source of rumors that turn out to be completely unfounded after the fact, but this is the risk part of exploring a new design.

BTW, note the structural tube (6).  The opposite end of it connects near where the duct heads into the bellhousing (2).

Audi has a history of race testing new technology and only telling us after the fact.  Recall the direct injection on the Audi R8 in 2001 and variable geometry turbos last year on the R15?  Could Audi have homologated the R18 as a hybrid, demonstrated it to the ACO in secret, and now have it in place?  We know, it seems a bit of a stretch.  What's that acceptance process anyway?  Seeing how public Hope Racing's was, maybe this is completely unrealistic.  

With a little logic from Sam Collins and we're all straightened out.  Sam points out that any hybrid would have prominent stickers saying as much to warn track marshals (high voltage), not to mention it doesn't seem to be realistic to keep the ACO pitlane test secret.

So clearly the cooling ducts are only cooling the carbon rear structure and those items that are piggy-backing along the way?  That's the easiest explanation, and frankly, most likely too.  Ultimately whatever the cooling need, it is all very deliberate.  One would think if it was only to cool the bellhousing a simple NACA duct or two in the engine cover would suffice.  
Though feel free to join us and ponder away...
Mazda 787B>>John Doonan has told us that Johnny Herbert himself will be doing the demonstration laps in the Mazda 787B at Le Mans on Saturday.  Johnny is of course one of the three drivers who won in the car in 1991.  Bertrand Gachot and Volker Weidler were Herbert's fellow teammates that year.  It had been previously annouced that American actor Patrick Demsey would pilot the car in Thursday's demonstration runs.

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Peugeot 908, Spa 20116.5.11

>>Peugeot's unfortunate practice crash at Spa this year gave us, and everyone on pit lane apparently, a really good view of the 908's rear end. You can bet Peugeot was more than a little irritated at the track side clean up crew for not flopping the remains of the engine cover onto the car.  Thanks marshals (and Benoit Maroye)!

The 908's water radiators are mounted forward, similar to the position they had on the 908 HDi FAP, and partially exit out the louvers in the vertical face of the side pods.  We surmise the oil coolers are in a similar position as on the HDi FAP too, tucking in next to, though outboard of and slightly overlapping, the intercoolers.  The roof intake feeds the turbos.

Brakes are cooled via the snorkels in the engine cover stuck on the leading edge of the fenders.  Note the baffling in the engine bay ahead of the rear wheels to better control airflow through the car.  The Audi R18 has similar.
Peugeot 908, Spa 2011The first detail to point out is the carbon fiber bellhousing (1).  This is the year for carbon fiber in the gearbox and bellhousing areas on LMPs.  But  this isn't treading new gound.  In Formula One, back in 1998, Arrows was the first team to create an entire carbon fiber gearbox case.  That it has taken this long for the concepts to be used in sportscar racing must simply come down to trying to find every last ounce in order to have better control over weight distribution.  It certainly hasn't been about a technology hurdle regarding the applications of high temperature epoxies and carbon fiber; they were good enough in '98 and they're even better now.  But with hybrids set to show up in full force in the next couple of years it makes sense to start ticking through items on the car and pulling weight out where one can.  

We understand the 908's bellhousing will serve dual purposes once the car is "hybridized."

The 908's suspension is actuated by a pushrod (2) as one would expect.  Torsion bars (3) and rotary dampers (4) are mounted to the side of the bellhousing.  The third spring (5) and anti-roll mechanism (6) are located on top.  

The carbon bellhousing is the mounting point for the leading leg on the upper and lower A-arms as well as all loading going into the torsion bars, dampers, 3rd spring and anti-roll mechanism.  Thus it's not too hard to imagine that its layup is not dissimilar at all to the monocoque considering similar loading inputs but narrower cross section.

Compare the 908 with the 908 HDi FAP and note how much slimmer the gearbox is.

Peugeot has retained that very interesting swirl detail on the primary intake plenum.  Recall its purpose was to maximize the length of the intake trumpet.  At the tangency between the round plenum and the trumpet, the trumpet continues to rotate around the plenum in a helical fashion, through approximately 270 degrees, instead of dead-ending perpendicularly into it.  This allows for a much longer intake trumpet without the need to raise the height of the plenum to accommodate taller intake trumpets (thus keeping the trailing edge of the engine cover that much lower).   
Peugeot 908, Spa 2011The diesel particulate filters tuck in either side of the engine and behind the turbos.  Note the proximity of all the hot bits to the bellhousing.  Modern high temperature epoxies can withstand temperatures approaching 475F before Tg issues (thermal stability) begin to rear their ugly head.
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Audi R18, Spa 2011>>Similar to how the shots were snatched of the Peugeot 908, it was a brief misfortune for the Audi that allowed David Legangnuex to snap the R18's bits. A rear underfloor swap meant the Audi team was temporarily unawares and that's all she wrote.
Audi R18, Spa 2011The Audi's rear end is as expected: pushrod (1) to torsion bars (2), teloscopic dampers (3) angled to meet the bellcrank, heat shielded 3rd spring (4).  

But the most interesting thing is the rear carbon structure.  The R18's is very different than the Peugeot 908's in that it is much more intricate by extending the full length (5) of the car and that the gearbox cradles inside the open ended structure.  
All rear suspension pick ups mount to the carbon.  The trailing arm pickups are supported by metallic structures (6) behind them that "stitches" each side of the open ended carbon structure together.  Note the forward drive shaft angle.

With the gearbox isolated from suspension loading, the gearbox wall proper now doesn't have the be as robust.  So a thinner wall and a
much simplified casing in general means less weight, one would think.

But we hear there are other purposes behind the structurally isolated gear casing.  ACO reuglation Article 1.12 defines the main casing of the gearbox as:

"Casings that receive or transmit loads from/to the chassis or from/to mechanical elements other than those which are part of the gearbox or the differential."

Note the wording, the ACO themselves define the gearbox as the casing that carrys the loading between the chassis and suspension.  So in theory, if one can put the suspension loading into something else...does the gearbox cease to be the gearbox as defined?

With that being the regulatory definition of the gearbox, we look at the sporting regulations which state:

18.9 - During the race, under pain of Exclusion of the car, it is forbidden to change:

− the engine, i.e. the cylinder head(s), cylinder head, cover(s), oil pan and engine block, parts that will be attached together by means of seals,
− the main gearbox and differential casings,
− the chassis or the monocoque structure

Has Audi designed a gearbox that meets the letter of the regulations and allows them to replace it if need be during the race?  Maybe.  But the question is, when is the last time Audi ever had a race altering/ending gearbox failure?  It seems like a situation where Audi thinks they're adding value by addressing a possible issue, but you have to think they're leaving themselves vulnerable to unintended consequences given the nature of the solution.  Clearly Audi had justification for going the route this year.  But it just seems like an extreme solution for a problem that doesn't historically exist.  

We're not 100% convinced this is Audi's justification for their rear carbon structure, but we have to admit it does seem Audi have found a loophole to do just as we've described.  Watch this item on the car and perpare for Peugeot to have an issue with it if indeed this is the case.
Audi R18, Spa 2011The rear structure that carrys the rear wing mount, exhaust pipe, and rearmost section of the underfloor plugs into the back of the carbon gearbox cradle via mushroom pins.

Oak Racing Pescarolo 01, Le Mans test 2011>>A few weeks ago we posted a really interesting image, taken at the Le Mans Test Day, of Oak Racing's rear wing flap.  We had a think, talked to a bunch of people, and have the answer as to what's going on there.  This was the process:

Since the 2004 LMP1 regulation changes (and even before that with the LMP900 regulations), the ACO have mandated a gurney on the rear wing flap that is 90 degrees to the plane connecting the top of the wing to the trailing edge (see FIA Drawing 258-8 in Article 3.6.3 of the ACO regulations).  Initially the mandated height was 15 mm, then in 2009 this was raised to 20 mm.  2011 saw the introduction of engine capacity reductions for LMP1 resulting in the loss of about 100 horsepower for the top diesel LMPs.  This has led to a trend shift in aerodynamics development from pure downforce generation to drag reduction and efficiency first, downforce second.
 
While it is only a small detail when looking at the entire car, the mandatory 20 mm gurney is even more of a liability than in years past.  But there's precious little that can be done about it...or is there?  

First seen at the 2011 Le Mans test day, Oak Racing have hit upon a clever design execution that maneuvers around the gurney regulation.  Ultimately the concept is a regulatory work around and nothing more, though more on the specifics in a moment.  But getting to this conclusion was fraught at first.  Initially it was suggested that the protuberances were designed with pure aerodynamics in mind; discussions were rampant about the bumps acting as vortex generators.  There was even mention the bumps were utilizing an aerodynamic concept seen in nature and on of all things, whales.  Yes, the giant mammal kind.  

Apparently scientists have always been puzzled about whale’s agility given their size.  And when researched, they took note of bumps on the leading edge of whale fins.  They came to the conclusion the bumps help reduce span wise leading edge flow migration and locally better organized the water flow leading to a much more efficient fin (or wing).  Hey, don’t shoot the messenger, I’m just repeating what I read.

I must admit I wasn’t convinced that was the cue Oak Racing had taken, though admittedly I had nothing else.  Apparently the research is three years old, and lacking direct access to their numbers, one has to utilize the school of observation.  And the best place to do that is to observe what’s going on in F1, the “bleeding” edge of motorsports aerodynamics.  No one has, to my knowledge, shown up on a F1 grid recently with a wing that had bumps or similar on the leading edge.  

Oak Racing rear wing flapAt about this time I received an email from a former colleague who is now with an F1 effort, asking me, of all people, what I knew about the Oak Racing wing flap.  Lacking anything else, I repeated the rather weak-sauce story about the whales.  Yeah, I did.  But the fortunate thing for me was that in the email ping-pong the answer shook out.

Ultimately it's pretty simple.  But first you have to think about the wing in cross section.  The mandatory 20 mm gurney has to be perpendicular to the line connecting the top of the wing to the trailing edge.  But Oak Racing has increased the height of the wing opposite the “conventional” cross section in an alternating pattern (the bumps).  And when you connect the top of the bump to the trailing edge, the perpendicular gurney is leaned back relative to the conventional section (approximately 30 degrees in our example).  And as the top of the wing is relatively insensitive (note that the important low pressure side is untouched), any loss from the bumps is more than made up for by the alternating gurney angle reduction.  

Throughout all of this I was finally able to reach Oak Racing's Technical Director Christophe Chapelain.  Chapelain immediately confirmed the concept was indeed a rules work around driven by the desire to reduce drag.  Says Chapelain, “The gurney is one of the most important piece for the drag.  It (the idea) came from a sort of brain storming.”  Team aerodynamicist Nicolas Clemencon utilized CFD to flesh out the concept and followed that up with wind tunnel testing at RUAG in Switzerland to validate.  The result, according to Chapelain, is the same level of downforce for slightly less drag.  Chapelain also indicates that there is some negative interaction from the bumps (flow separations), but not enough to take away from the positives.  The wing is also just on the edge of improved L/D; the flap wasn't used at Spa because at higher downforce levels it's more efficient to use a standard flap without any bumps.

And Oak Racing's concept hasn't been dismissed outright and rival outfits are already mulling the possibilities.  “Well, it depends on how big the negative effect of the flap top surface modification...I will know more after trying it, possibly in a nicer way,” this according to one aerodynamicist for a current LMP project.  One wonders if there's been enough time between the Le Man test and the race...we'll see soon enough!

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ęCopyright 2011, Michael J. Fuller