Mulsanne's Corner

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Le Mans 2015

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

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Toyota TS040, Le Mans Test 20156.15.15

>>I brought my camera with me when I headed over to the Test, though I didn't have much time to utilize it.  But between my shots, and Sam Collins' of Race Car Engineering, I'm pretty confident we cover most angles.  I'll be updating this page over the next few days, as the race unfolds, etc.

>>Toyota TS040
Toyota TS040, Le Mans Test 2015Outboard strakes ala Toyota TS040.  Toyota has a different take as they've created a mainplane/flap arrangement utilizing two strakes that are very much wing shaped, nested them together to create a slot gap, and hung them vertically.
Toyota TS040, Le Mans Test 2015Having a look underneath and Toyota actually has two pairs of strakes located under there.
Toyota TS040, Le Mans Test 2015Toyota's engine cover trailing edge appears to be particularly tall compared to Audi and Porsche (1).  The height is also raised at the outer corners of the exit (2).
Toyota TS040, Le Mans Test 2015Toyota's lower rear fender bodywork coke bottles inward to draw air in across the cheese wedge and into the base area, though they eschew the Porsche/Audi trend of opening up the leading edge of the lower bodywork and directing air inboards with a strake.  Instead, the lower bodywork is offset inboard at the leading edge, and this has the affect of grabbing air tumbling off the tire and directing it to the base area.
Toyota TS040, Le Mans Test 2015The TS040's rear wing endplate extension comes in the form of a trailing edge extension that comes to a point.
Porsche 919, Test, Le Mans 20156.13.15

>>Porsche 919
Porsche 919, Test, Le Mans 2015Perhaps someone can make sense of what's going on here, though Porsche thinks it's totally secret squirrel...Porsche doesn't use blue blankets like Peugeot used to.  No, being the asshats they are, they just position people to stand in front.  But these guys weren't really paying attention to where I was versus where they were so a small opportunity presented itself...

Porsche 919, Test, Le Mans 2015At the base of the windscreen are two scoops either side of the car centerline.  I'm not sure what they cool, and they augment the large cooling slot located in the leading edge of the nose.
Porsche 919, Test, Le Mans 2015It's different in the details compared to Audi's, but at the end of the day it's a small strake mounted to the most outboard part of the floor behind the front wheel, so how different is it really?  However, the primary difference is the leading edge on Porsche's strake rakes forward at the bottom to match the trailing edge line of the tire.

In general the Porsche and Audi have different aero philosophies, but in some of the details they are very similar.  Given personnel have crossed lines between the two programs, this isn't too surprising.
Porsche 919, Test, Le Mans 2015I noticed this cute little gurney attached to the center of the 919's engine cover.  I'm not sure what exits out of the opening below it, but Porsche feels it is important enough to need some extraction.  My intuition is that the gurneys are too small to be about downforce.
Porsche 919, Test, Le Mans 2015Porsche does similar to Audi (and everyone else, this must be a pretty profitable area) and allows outboard air to flow inboard via the cutout (1), directed by the strake (2).

Also note the diffuser strakes are trimmed well short of the diffuser trailing edge.  
Porsche 919, Test, Le Mans 2015Porsche's rear wing endplate leading edge extension alters in camber as it moves up the endplate's height, so it's trailing edge is further back lower on the endplate
Porsche 919, Test, Le Mans 2015The very leading edge of the endplate extension is angled outboard.
Nissan GT-R LM, Test, Le Mans 20156.12.15

>>Nissan GT-R LM

The most technically interesting prototype this year is inarguably the Nissan GT-R LM.  I'm the first to disdain a marketing driven program, and it's easy to think that's what's going on with the Nissan given their openness and proactive social media campaign.  But the car, in spite of the obvious early-days issues (remember, this is the car's first race event), has technical merit.  As one Nissan engineer put it to me, "The numbers work, they make a lot of sense."  And Nissan, Bowlby, and the gang wouldn't have gone in the direction they went in if that wasn't the case.  So while the program appears marketing driven (a bad thing in my opinion as marketers know shinola about race car design), in reality it is driven by engineering first and foremost, the marketing plonks are simply doing their job and telling us about it, warts and all.  And that's reality; racing is hard, period.  In the mean time you don't hear shit out of Toyota, Audi, and Porsche, and the question has to be asked, what are they REALLY doing to promote the sport in the end?  Blue blankets and bullshit is what.
Audi R18, Test, Le Mans 2015The answer to the "why."  Without an engine, gearbox, or cooling system in this area the most elegant and tidy rear end can be designed.  All for aerodynamics.  The tunnels are fantastic, you can see almost clear up to the front of the car.  It was tempting to want to crawl up into them...  
Nissan GT-R LM, Test, Le Mans 2015The Nissan's rear fender turning vanes are nothing particularly special and it's very clear there's still a ton that can be done to optimize the car aerodynamically.  All one has to do is look at the detail work on the competition to get an idea.  I think this speaks to the, I hate to say it, initial rushed-nature of the project.  And this really is my primary criticism of the program, it all appears to have been pushed out about 6-9 months too soon.  And this aligns with the rumors of a 7 day, 140 hour, work week, in the extreme cases.  But I recognize that the fault probably lies elsewhere as Bowlby has been around long enough to know what it takes to execute a project like this.  The fault more than likely simply came down to timing; Nissan signed off when they signed off and the time plan unfolded from that date.  I can imagine things will calm down post-Le Mans with the running of only two cars in the WEC.
Nissan GT-R LM, Test, Le Mans 2015Looking at the turning vanes from the other direction and we can see that the middle vane (1) actually is a extruded pontoon shape, not a simple 2-D vane.

An interesting detail is that a "shelf" (2) has been created inboard of the rear tire.  It's a small carve out that creates a horizontal shelf.  Ultimately it's probably insignificant and has more to do with the fact that the narrow nature of the rear tire means the inboard face of the rear wheel well doesn't form the immediate outer wall of the diffuser.
Nissan GT-R LM, Le Mans 2015Much is being made about the car's apparent lack of performance.  I feel the first thing to understand is that the twin-flywheel hybrid system is simply not working.  So the concept has gone from 4 wheel drive, to 2 wheel, front only drive.  And then following the Test the admission was that hybrid simply wasn't being used at all.  So power was solely coming from the combustion engine, roughly 500 hp, and the times reflected that; 20 seconds down.  The emphasis has been on the loss in power from the hybrid for acceleration, but perhaps more importantly, the GT-R LM is suffering from a lack of braking given zero harvesting from the hybrid system.  And this appears to be an issue they've been dealing with for a while as it is what directly lead to the switch from 16" to 18" tires at the front in order to use larger brakes.  So you can imagine the performance hit to power and braking is significant, and all the while they still have to lug around the hybrid system as so much expensive ballast given the rules regarding LMP1-H.  How much of their 20 second deficit revolves around the hybrid issue?  A huge chunk, thus there's a solution once the system is sorted and only a neophyte would condemn the entire concept considering this problem.
Audi R18, Test, Le Mans 2015>>Audi R18
Audi R18, Test, Le Mans 2015So Audi's front fender ducting is slightly revised, but starting from the top; 1 LED light cooling duct, 2 is now closed off compared to the open duct seen testing at Monza, 3 directs airflow into the front fender well as a means of mitigating negative wheel well interactions with air moving past the front wheel opening, 4 is still unidentified, 5 exhaust exit for LED light cooling duct.  

However, another theory to 3's ultimate function might have something to do with the very outboard turning vane (image below).  Could Audi be putting more air outboard to interact with the outboard turning vane downstream?
Audi R18, Test, Le Mans 2015Audi's very outboard turning vane is fairly simple, however Porsche, Toyota, and Rebellion follow suit.
Audi R18, Le Mans 2015Given the outboard turning vane's (2) position relative to the front fender duct (1), it's reasonable to think it might have influenced the use of that duct and that they work in conjunction with one another, the duct brining more flow volume to the turning vane.
Audi R18, Test, Le Mans 2015The front wing adjustment mechanism.  It would seem to require a simply socket headed ratchet to make flap angle changes.

Also note that the winglet elements are open on the back side.  
Audi R18, Test, Le Mans 2015The R18's integral rear view mirrors are designed to tuck behind the front fender trailing edge and reduce drag.  Though the trailing edge of the mirror, the point below the mirror, very much acts like a turning vane.

At least one competitor privately indicated they felt Audi's mirrors were outside the regulations.  But having a look at the rules there is very little that governs them so I can't see much wiggle room for protest as it's clear Audi has met the regulation for mirror area (100 cm^2) and has satisfied the scrutineers via the vision test (detailed under Art 17.4.2).

Audi R18, Test, Le Mans 2015At the rear Audi has opted to move the mandatory BHH from the top location to the inboard location.  The shape is optimized to reduce (and enhance) the impact these holes have on drag and downforce.
Audi R18, Test, Le Mans 2015Rear wing endplate extensions are making a come back this year with Audi, Porsche, and Toyota all indulging.  Audi utilizes a leading edge extension (arrow).
Audi R18, Test, Le Mans 2015The leading edge extension joggles into the leading edge of the endplate.  Note the  extension has thickness beyond the 10 mm constant thickness regulation that governs endplates; the extension is considered "bodywork" and doesn't fall under endplate regulations.  Furthermore, the extension bends slightly outboard.  In the end though this is a subtle performance enhancer, "fine tuning" as some one mentioned.

While we're here looking at the rear wing, note the lack of gurney on the flap.  I don't think I saw a flap gurney on any of the LMP1 cars.  This probably speaks to Le Mans and the over riding concern for drag reduction.
Audi R18, Test, Le Mans 2015Close up of the rear.  Audi has opted to open up the outboard  vertical surface up to 200 mm above the reference plane (1).  Note the vertical strakes mounted to the top of the cheese wedge (2). We first saw this opening back in  2011 on the HPD ARX-01e LMP1.  The opening and the strakes work to draw air inboard and help with base area infill.
Audi R18, Test, Le Mans 2015For 2015 the ACO mandated a minimum 2" gap above the diffuser at the bodywork trailing edge.  The R18's is that height across the entire width of the car.  Note the proximity of the engine exhaust.  These are also regulated as to how close to the trailing edge they can be (no less than 300 mm).

ęCopyright 2015, Michael J. Fuller