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January/February 2015

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Race Transmission Specialists From vintage rebuilds to technical design services... 2.16.15



>> M issed in all the Nissan excitement for the past two months was the release of the 2015 regulations. In year's past I've gone through the year to year regulations noting the updates and changes. But to be honest there really isn't any need this year as the 2015 chassis rules are largely unchanged from last season. Instead I want to concentrate on two changes for this season, one not even addressed in the initial 2015 rules but instead released as a regulations “clarification.”



Everyone should recall the news, broken here as the Le Mans 2014 race weekend unfolded, regarding what can only be described as Toyota's cheater rear wing. While the mainstream media has been obsessed with the latest defective product lawsuits and the legal arguments of talcum powder lawsuit lawyers, we have been focused on the latest developments in the racing world. The test weekend had seen a small controversy surrounding Porsche's obviously flexible rear engine cover trailing edge. But Porsche showed back up for the race with a now-rigid trailing edge. Toyota had, on the other hand, spent quite a lot of time and money in developing a rear wing assembly that, when at speed and under load, rotated to reduce the entire assembly's angle of attack with the intention of a large drag reduction. And these facts didn't start to come out until the race was essentially underway; the Toyotas had already passed scrutineeing. But the evidence was immense, with many diagrams and animations, presented here and here, about the presumption of how it all worked. Perhaps as surprising was little, if anything was said in the sportscar media, and no comment was ever made publicly by the ACO. For me it was the technical story of 2014.



However, with the 2015 regulations the ACO has tangentially admitted that someone was up to something in 2014. It comes in the form of volumes of new regulatory wordings regarding flexible bodywork, redefinition of the mounting of the rear wing, new test procedure regulations to check the rigidity of the rear wing and assembly, new wording regarding the front skid and it's rigidity, etc.



There are quite a few new regulations that specifically address flexible bodywork for 2015 though I'm not going to look at that in detail. If you're curious, put your eyes on Articles 3.5.4 /b, /c, & d/, 3.5.6 d/ & e/, and 3.6.1.



The revised regulations for the rear wing, however, are particularly telling, starting off with 3.6.2 c/, “The rear wing must be rigidly (rigidly secured means not having any degree of freedom) attached to the chassis or to the transmission casing or to the rear absorbing structure of the car.” Article 3.6.2 c.4/ is completely rewritten with all new testing requirements for the rear wing assembly. The foremost is that the rear wing endplates are now required to be connected to the bodywork, unlike last year. Furthermore, the legality cheese wedges at the rear end of the car are now also scrutinized with their own load test. Ironically these modifications to the regulations completely prove my suspicions last year about how Toyota's drag reducing rear wing assembly functioned!



The second change for 2015 amounts to a clarification. Recall last season the emergence of turning vanes attached to the front brake duct assemblies, and projecting downwards and below the reference plane? Well the ACO announced in September, ahead of the Austin WEC round, in response to an Endurance Request document, #14-R0058-LMP1-TOYOTA, yes, issued by Toyota, that they would look into these turning vanes, but not until after the season was over stating in a Decision of the Endurance Committee, #14-D0032-LMP,



“Taking into account various multi recent exchanges about the clarification of brake scoops summarised in the Endurance Request 14-R0058-LMP1-TOYOTA and some reported evidence of previous historical allowances not in accordance with it, the application is postponed and will not be enforced for remaining 2014 races.”



Endurance Requests are ways manufacturers can request clarifications about unclear technical concerns, bringing them to open discussion and a corresponding response and direction from the ACO.



Thus the ACO issued Decision of the Endurance Committee, #14-D0035-LMP clarifying that turning vanes are here to stay but with a couple of provisions. For starters they've clarified that unsprung elements must comply with Article 3.4, so anything hanging from the brake duct assembly is considered as a mechanical element and, “As viewed from above, in side elevation, from the front and from the rear, the bodywork must not allow mechanical components to be seen...” This would effectively eliminate hanging turning vanes from the brake duct assembly as Art 3.4 would very much restrict the depth to which they could project.



Additionally, forward of the front wheel centerline unsprung elements must respect Article 3.5.4 in regards to depth. So this means that in a box defined as 500 mm either side of the car center line laterally, and projecting transversely from the leading edge of the splitter to the front wheel centerline, all elements must be 50 mm above the reference plane. This is the box that also mandates the center portion of the splitters to be raised by 50 mm. Any element outside that box must be at least 10 mm above the reference plane.



However, the ACO has indicated that elements attached to the car aft of the front wheel centerline are allowed to project to the reference plane (Z=0), though not below. So the restrictive area relative to last year is ahead of the front wheel centerline. While anything behind the front wheel CL, up to 400 mm rearward and 770 mm inboards, is in a free zone and can project to the reference plane.



The net result? I'm told that the revisions to the turning vanes rules have essentially led to zero changes in downforce; the fixed nature of the 2015 turning vanes and different position has simply been an overly complicated, and expensive, exercise for no change in performance. 2.1.15 continuously updated



>> S o for two months I've been laying out the rumors and speculations as relating to the Nissan GT-R LMP1, ticking through the logic when details were lacking (and oh were they lacking), and in essence "drawing" the car as the information came to me. It was always going to be a monster, as we all came to realize...well all is revealed tonight and Nissan has provided quite an astonishing level of detail. No blank spaces in the technical detail, photos galore, drawings, just about anything you can think of. Certainly no blue blankets, no standing in your way to obscure a photo, no yelling, none of the BS.



Though frankly, if you've been reading these past two months a lot of these details are already known. But before I dig in, do yourself a favor and read up here, and below, to get acquainted first.



Where to start? Well it's pretty obvious. The engine. Front located. Why was this so hard to believe? And there were still doubters even after the images started coming out. Front wheel drive. So as mentioned in December, the internal combustion engine (ICE) powers the front wheels. The interesting slant is that the twin flywheel Torotrak developed KERS, while located in the front of the car and underneath the driver's feet, and harvesting from the front, powers the rear tires, but can also power the fronts as needed. At the moment there are issues with getting both units to work, and it's not an option of addding or removing flywheels as desired as the flywheel unit is machined as one housing for both. And the engine? The Nissan guys call it the VRX 30A NISMO; it's a 3.0 liter, twin-turbo, direct injection, 60 degree V6. It comes from Cosworth. No, it isn't based on their stillborn F1 unit, and it isn't 1.6L. Forgive me?



Radiators head the front wheels. The carbon fiber crash structure protrudes forward from centerline with the radiators either side and is clearly hollow, doubling up as an inlet duct. A duct for what? Well the turbos of course. Solid carbon tubing emerges from the rear, and either side of the crash structure, heading to the turbos which are located towards the front of the engine.



A cast metallic front bellhousing/gearcase is located just aft the radiators and heads the engine. The entire front end assembly, splitter, radiators, radiator housing and related exit ducting mount to the crash structure. And this entire unit bolts to the front of the gearbox/bellhousing. There are some drawbacks to a front radiator arrangement with the primary one being susceptibility to damaging impacts. So you can hope that the front splitter/radiator housing/exit ducts are tough, and more importantly, it's easy to change the entire assembly. Though I'd rather not have to do that with a hot engine.



The suspension hangs off the gearbox/bellhousing as well and the ICE power, in addition to maybe the KERS dischard (depending on strategy at the moment) is transmitted through the center and to the half shafts. Looking from above, the half shafts are at a slight angle forward. The engine is in the middle of this all the mechanical soup; mounted longitudinally and just behind the front wheel centerline, it certainly dominates the environment. As mentioned back in December, the twin turbo exhausts poke out of the top of the hood, just ahead of the wing screen. Their placement does make you wonder what that will do to driver night vision. The front mechanical package bolts to the forward part of the tub, the monocoque is as would be expected. Mechanical details become a bit fuzzy going rearwards. Images of the rear show a composite rear end structural composite outriggers to which the rear suspension mounts. These outriggers are offset from centerline, allowing space for the large flow through tunnels I speculated about (more on that in a minute).



The rear suspension mounts to these outriggers and clearly they are structural. The rear suspension is a throw back to the Group C/GTP days in that the spring/damper is direct acting on the lower A-arm, no pushrods here. It's done this way in order to eliminate pushrods from the tunnel sections, suspension elements too, as the entire suspension unit is contained outboard and in the immediate proximity of the outriggers.



Recall the drop gear uprights? It all comes to play in the rear; the half shafts are raised to clear the tunnels and the suspension mounts to the outriggers, meaning there's absolutely nothing situated in the tunnels. The inner section of the rear structure is tear dropped at it's trailing edge, further encouraging the best aerodynamic relationship between the car and the internal airflow.



All the air scooped up at the front by the front splitter/diffuser exhausts into the tunnels that run either side of the monocoque, down the car's wheelbase, and out the back of the car into the low pressure area located there. The rear end of the car is designed to provide ample exit area with the rear deck height being much taller than the norm. A gurney on the trailing edge of the tail further enhances the low pressure encouragement. It's pretty clear the tunnels rely on elimination of the rear halfshafts and suspension. Viewing forwards from the back of the car and you can see almost to the front of the car by looking into the tunnels. It is pretty clear that the primary purpose of the full length ducts is front diffuser activation and base area infill; pure aero.



Nissan admits in their press material they will struggle to make the weight minimum with Bowlby stating, "We’re going to be really challenged to make our weight target of 880 kilos for 2015 when half of the weight of the car is the powertrain: engine, ERS and the driveline." And today I'm hearing the initial car is dead on the minimum without even the KERS installed. This will be a great challenge as the car is all engine, KERS, and driveline components from one end to the other. The technical specification provided confirms smaller than the norm wheel diameters front and rear, 16" compared to 18" for the Audi. The 16" wheels in lieu of the small diameter brakes, from what I can understand. However the overall tire diameter is the same as the Audi, 31/71. And while the rear tire is a completely different beast, 20/71-16, it still has the same overall tire diameter, 71 cm, as the Audi. So that means with 16" wheels, and 71 cm (28") diameter tires, you have a tall sidewall.



Looking at tire widths, the front tires are 13" wide (31 cm according to Michelin nomenclature) and only 9" wide (20 cm according to Michelin) at the rear. The tire dimensions are completely driven by aerodynamic and weight distribution desires. With more weight forward they'll be less weight transfer front to rear. The preliminary front/rear weight distribution guesstimate is 61/39. This is calculated by generating the total contact area for a front (31 * 71= 2201) and a rear (20 * 71= 1420), calculating the total area combined (2201 + 1401= 3621) and then generating a ratio of tire area to total area for each (2201/3601 = 61%, 1420/3601 = 39%). The idea being the contact patch % of the total is in a similar relationship to the weight distribution. It isn't perfect, but it's a good starting point. So with only 39% of the weight in the rear there's less need for rear contact patch, and the narrow tire is a aerodynamicist dream as bonus, reducing the tire-to-underfloor interaction. Nothing in the tech spec confirms the narrowed rear chassis, and the drawing provided seems to blow that idea out of the water mostly.



Yes, the Nissan has a rear wing. Again, this idea, the rear wing delete, was, in my mind, a Le Mans test item given all we know about the the concept, reduced drag, weight forward reducing need for rear downforce, etc., etc. Nothing in the press literature addresses this, though informed sources state, “We will run Le Mans spec aero, etc., even at Silverstone.” Regardless, it appears integrated into the car design and in the end I was completely out to lunch on this. But with a 61/39 weight distribution, aero balance will trail around 58/42. 42% is about 10% less than a mid-engined car, so rear downforce will have to be reduced, thus the rear wing, while much more substantial than "vestigial", is reduced. Interestingly enough the 58/42 aero balance guess is dead on though low-side, and back to front, of what a mid engined car typically runs (typically run between 45-42% front). In the end this was my unintended contribution to the "wild rumors," the rear wing delete idea. Though it would certainly have been interesting!



Nothing has been said about what MJ energy class the GT-R LMP1 will run in, that is still a bit of a moving target at the moment. Total system power output has been addressed and Nissan has backed away from the 2000 number, admitting it was a target, and perhaps one that isn't currently achievable. They are admitting to 1250-1500 for the time being.



The new Nissan prototype is a continuation, and execution to the regulations I might add, of the concepts started with the DeltaWing, continuing to the ZEOD, now culminating in the GT-R LMP1. It's a connect-dots car, much like the DeltaWing. Starting with a desire to drastically reduce drag, leading to a front engine to move weight forward in order to reduce rearwards weight transfer, and to shift aero balance forward in chase of weight distribution, it all makes elegant sense in the end. Mulsanne's Corner Book Store

A selection of sports car related DVDs and books, with a technical slant. 1.31.15



>> S o roughly 5 hours after I wrote the below, Nissan releases this (left) via @Nismo. Soooo, I guess that means tune in on Monday? Now it turns out, Monday morning 10:00 (AM) Yokohama, Japan time. So just barely Monday morning in London, UK, 01:00 (AM), and 20:00 (8:00 PM) on the East coast U.S., thus Sunday evening. I nearly screwed that one up!



Oh yeah, note the pretty clear lack of a rear wing in that image...



Just say'in... Mulsanne's Corner Paddock

Motorsports and other interesting merchandise. Or, cleaning out my house. Images courtesy and copyright Nissan and Jalopnik



>> G odzilla has gone a bit quiet ahead of the official debut tomorrow, though this is understandable. But if you listen closely, you can hear her thumping around off in the distance and the discussion is taking a somewhat more realistic tone. Tempered expectations? No, nothing officially at least.



One of the items I'm hearing is that there seems to be troubles with the flywheel KERS, such that up until recently the Nissan GT-R LMP1 struggled to do multi-consecutive laps without the system overheating. And while I'm told that the KERS is working “perfectly” on the dyno, I also understand that's not exactly the case. And of course there's still the issue of getting it to work in the chassis.



I now also have a clearer description of the KER system; it's actually a two flywheel system with each placed next to one another, either side of car center line, underneath the driver's feet. Harvesting power input for the system are the front wheels. I don't have a description of how the twin flywheel system work, but it is my understanding that there are issues with getting both to work “together”, and as such it has “half” the power expected. The rest of the accompanying hybrid components are underneath the driver's leg, with a single prop shaft projecting rearwards, on car center line, powering the rear wheels. My best guess is that the GT-R LMP1 will be running in the 8MJ energy class. Anything less suggests significant issues with the KERS given the usable time vs power drops dramatically the lower MJ class you're in. So if Nissan does indeed have 2000 total system hp, and they opt for the 2MJ class for example, it means they will have a mere 2 seconds to expel that 2000 hp (~1400-1500 from the flywheel) at max power. In contrast, the 8MJ class would give you roughly 7 seconds of release at max power. So bigger potential power release means you'd migrate towards the larger MJ class in order to maximize the time across which to release max power (or even partial power).



Another issue is interesting in what it reveals. I'm told that the Nissan is utilizing much smaller diameter than conventional brakes (smaller than even P2 brake diameters apparently), with the idea the KERS provides the braking difference upon harvesting, as is being done in F1. The issue seems to be that the KERS isn't providing enough mechanical drag/braking force, though I'm told the setup will be OK for Le Mans. There's also been a suggestion that both the front and rear wheel diameters are smaller than conventional, as well as a confirmation the rear diameters are smaller than the fronts. With the smaller diameter wheels come tall side wall tires and I understand there have been issues with the vehicle dynamics and a suggestion of a reconsideration of the small tire concept. I can imagine what that would take, and affecting a major redesign such as that could be detrimental at this stage of the program.



About that rear wing...the car concept was developed without it though it has become a necessity as total downforce levels have increased, as I mentioned in my last update. However, it has been reiterated to me that it is little more than vestigial as the elimination/reduction of the rear wing is central to the entire theme. And it's expected the GT-R LMP1 will run Le Mans spec aero at testing, and the races, ahead of Le Mans. With or without rear wing? Watch this space as well...

What's this about Nissan having only done 100 kilometers of testing? I hear that's completely rubbish. However, I do wonder how constructive their testing has been. The impression I have is that there's a steep learning curve with this car, and perhaps certain systems, the KERS for example, are in need of further development. And as such I'm personally not expecting much for reliability up front. And if they're lacking in reliability at the moment, you can be sure that testing has been frustrating. Some are saying, “Give it a year of development.” I hope a year is enough to reveal the correct road taken from a concept standpoint and to shake any bugs out.



I'm still planning on tuning into the Super Bowl though I'm not really sure how that will help me report post. As of now there have been no official Nissan press releases even informing media of the Super Bowl event. While I don't expect Nissan to chatter about their car ahead of the debut, I do expect them to give a heads up. So for some reason they haven't, and as a result I have no idea what I'm even expecting other than a 90 second commercial. I have set the DVR to record in HD, for whatever that's worth. I suggest everyone should tune in. You're welcome Nissan!



Oh course there's the distinct possibility the commercial is just a commercial with the official debut at some other time entirely.



Here's a Technical specification recap of what I've been speculating on since December:



Nissan GT-R LMP1



Cosworth developed twin-turbo V6, 550-600 hp, going out on a limb I'll say its 1.6L considering the F1 origin.

Front engined, front wheel internal combustion engine drive

Torotrak developed twin flywheel KERS located in front of chassis, harvesting via front wheels, power transmission to rear wheels

8MJ energy class, anything less than 6MJ= issues?

Total system power, “2000”

1900 mm overall car width at front, ~1800 mm overall width at rear

Smaller diameter front and rear tires than conventional with the rears smaller than the fronts

Smaller rear tire width than conventional, is it as simple as a front to rear swap as far as tire width concerned? Maybe.

Smaller diameter front and rear brakes, utilization of KERS braking during energy harvesting

No rear wing for Le Mans, low drag wing elsewhere

200+ mm high rear deck above diffuser TE to accommodate “flow through” cooling/front diffuser activator

Obvious things I've missed, many. Not so obvious things I've missed, many. Things I'm plain wrong about, many.

In the end it all sounds pretty wild and is certainly many, many tacks away from what's been considered the norm. Is all of the information correct? Probably not, I'm sure the pedants will inform me.



There is a little more than 24 hours away before we all know (hopefully, maybe?). All images courtesy and copyright Jalopnik



1.21.15



>> W hen it rains it pours, about 24 hours after our little amoeba friend appeared on the Net showing the Nissan GT-R LM LMP1 going through it's testing cycle at the Circuit Of The Americas, thanks to diligence on Jalopnik's behalf, more images, vastly more descriptive ones at that, pop up. It's an information bonanza!



So I've been reporting on the Nissan for over a month now with my first articles going on mid-December. No other outlets are writing about the program at the moment, instead they are presumably waiting for the official launch. Thus it puts me in the tight spot of being the only one willing to stick my neck out, and as has been seen, I've had to rely on a fair bit of speculation. That's nothing new to those who frequent my site. This process is about homing towards the truth so at times, to some, it seems as though I'm grasping at straws. The reality is the information is evolving and I'm adjusting my viewpoint with those updates. I'm augmenting source information with speculation as I don't have a clear picture; it's very obscured. But have I been so wrong? I'll argue the speculation has simply become more nuanced. And while I'll never talk about who my sources are, I will say this: Nissan's NDAs have been pretty effective and frustrating. That I've been able to dig up as much information as I have speaks to connecting the dots, from Delta Wing and ZEOD, to scraps of information here and there, to my always reliable cadre of sounding boards (you all know who you are) . And once you piece all that information and references together, at the end of the day the car begins to draw itself and it actually makes quite a lot of sense. Yes, I might miss on some of the specific details, but I feel I've been providing a pretty clear picture into the concept phase. A rear wing has appeared! For starters, I've always felt that the rear wing delete would be a Le Mans-only configuration, if I didn't make that clear. However, note that from the images it doesn't appear the Nissan is carrying much rear wing angle, and these shots were taken at COTA; a high downforce circuit. That should tell you something about design intent regarding the rear wing and it's overall importance. As to why it appeared, I've been told that the drivers felt the car was "dangerous" and needed a touch more rear downforce. The rear wing was then added based on that feedback. However, I still feel very confident that Nissan will run without the rear wing at Le Mans and that its addition was only necessary with the increased total downforce demands of higher downforce tracks.



Very early on in this process I was informed of the detail regarding the drop gear on the upright and raised half-shafts that I mentioned back on January 7. I was told this was because the Nissan had "huge tunnels" at the rear. I really didn't know if I should take that literally or not, and after confirming Nissan hadn't been given any dispensation regarding the underfloor from the ACO I tucked the “huge tunnels” thought away. Though I still didn't know what to make of the raised half shafts. So I came to the conclusion of the diameter discrepancy front to rear and that Nissan must be compensating for extreme halfshaft angles. It fit the rumor narrative at the time coming from AutoHebdo about smaller rear tires. But seeing the tires now, the front to rear diameter difference is small. So I don't think Nissan is compensating for halfshaft angle at the rear. But why the raised halfshaft? Back to the "huge tunnels" comment. Upon seeing the rear end of the car I'm struck by the very tall rear deck height and the complete lack of any sort of obvious front diffuser exit. The rear deck height is monstrous; for 2015 the ACO has mandated a minimum rear body trailing edge height of 50 mm above the diffuser. So one would expect to see the minimum (50mm), or thereabouts, given the trend towards zero heights the past couple of seasons. 50mm is 2”, and as a reference the diffuser exit height is a maximum of 200 mm tall. It's pretty obvious that the rear deck height is greater than 200 mm above the rear diffuser trailing edge. So clearly something is going on there. Now at the rear of the car, in the base area, is a very nice source of low pressure. Could there be some sort of tunnel, or ducting, projecting rearwards from the front of the car, through the side pods and along side the tub, and out the back? But what could the low pressure feed from the car's base area be activating? Regardless, this starts to perhaps better explain the raised rear halfshaft. Recall the Audi R15 ran into issues with their flow-through concept when it came to the rear suspension and half shaft, these elements increased the induced drag and made the overall concept a very tough argument in Le Mans spec. Thus I think Bowlby has raised the half shaft and incorporated a drop gear on the upright not to compensate for reducing tire diameter, but to pick that element up out of the air flowing through the duct, allowing for more effective flow-through. Presumably the upper A-arm is out of the flow to begin with and the lower A-arm intrudes into the diffuser tunnel more than likely.



But what is the purpose? Could the low pressure wake behind the car lend a hoovering effect to the front diffuser? This would explain the lack of any exits at all past the front wheel centerline as any interruptions, changes in direction, in the ducting would reduce pressure recovery. But is the trailing edge exit too far away to have any influence on the front diffuser? So is it only for cooling? Surely the two exit ducts towards the leading edge of the nose (the only two that can be seen on the entire car) are related to that. Though that doesn't seem to be enough for the presumed cooling needs of the car (water, oil, intercoolers). But there are also no obvious means of generating front downforce. No diveplanes even (remember these images are shot at COTA), and only a prominent splitter as a means to prduce front grip. And there are certainly no exit ducts of any kind related to obvious downforce generation. This car will need front downforce and the mandatory cutouts (Big Honking Holes, note Nissan has gone for the t op location option) in the front wheel arches certainly aren't enough to draw the front diffuser, creating the necessary front downforce.



We've seen similar details in the past, recall the boundary layer suction developed for the Nissan P35's large side pod oil cooler inlets. Utilizing the large area of low pressure situated behind the car, a slit in the leading edge of the duct drew off the thickened boundary layer ahead of the main intake. It was a simple and small detail on a mid-rear engined car which utilized the rear wake to also draw out the heated oil cooler air through the engine bay, past the engine, gearbox, and suspension, and out the back of the car. And it worked, even in that comparatively dirty environment. How much more effective would the low pressure draw of the base area be if the car design was optimized for this purpose and the rear end didn't have all the complications of a engine being in the way? So with that, what do you do with it? The answer could be very interesting. Watch this space. Looking at the side view and focusing on the wheels, it seems pretty clear the rear tire diameter is smaller than the front but that the wheel diameter is the same or very similar. Therefore I think there's less of a need to compensate for half shaft angle and the real reason for the upright drop gear is what I mentioned above and simply for aero reasons; to clear the full length ducts/tunnels that provide front diffuser activation. The front view affords a look at rear tire widths, based on the width of the rear fenders, and it does appear that the rear tires are narrower than the fronts.



At the front we can see what looks like the crash structure protruding forward out of the primary radiator inlet. It seems a bit awkward looking and I can't think of any reason why it wasn't better integrated into the design, assuming I'm right that it is indeed the crash structure.



These images unfortunately don't provide any corresponding visual evidence to the location of the engine exhaust exit. I was told they poked out the engine cover ahead of the windscreen, but the limited views available don't reveal that, or much of anything really, just lots of reflections in that area.



The side view mirrors are positioned just aft of the mandatory fender holes, presumably riding in part of the low pressure wake created by those holes.



At this point all there is left to do is to but wait for the official launch as these images certainly have satisfied a portion of my curiosity until then. 1.18.15



>> N issan has choreographed the release of two extraordinarily poor 1995 cell phone images of the GT-R LM testing at the Circuit Of The Americas (they can be seen in various forum and on Facebook). Taken with a pinhole camera (or etched on a rock, I can't decide), we can see what can only be described as a blob, or an amoeba, as seen from 2 miles away. However, the image seems to confirm that the blob is red, and perhaps white, and probably front engined. If you squint that is. Furthermore, given the much higher downforce nature of COTA than Le Mans, a rear wing blob can be seen (no surprise there, ultra low-drag only has a chance at LM) at the rear of the main blob. Maybe. Identifying any more details beyond that would be a supreme leap of faith, though I'm pretty sure that's Winston Churhill's profile there in the middle. Yes Darren Cox, I wrote 150 words about an indescribably shitty photo (no offense meant to the photographer of course). You're welcome. Mulsanne's Corner Book Store

A selection of sports car related DVDs and books, with a technical slant. 1.7.15



>> A couple of weeks further since Part 2 and more information is coming forward. I'm told that the flywheel KERS on the Nissan is actually in the front of the chassis, with a prop shaft running to the rear to drive the rear wheels. Furthermore, said sources have confirmed, without a doubt, that the combustion engine does indeed power the fronts tires, KERS the rears. My best guess about placement of radiators seems correct, mostly ahead of front wheel CL. And all of this, radiators/intercoolers, KERS, is purely for weight distribution. While the GT-R LM has nothing like the extreme weight distribution of the Delta Wing (30/70), like I mentioned last month, I do believe it is closer to 55-58% (or even slightly more) on the front, which ultimately means it has similar weight distribution numbers to a mid-engined car, but back to front.



I'm told that the Cosworth engine is a conventional twin turbo arrangement, conventional in this case meaning that the turbos aren't located in the 'V' of the engine and aren't being used for energy recovery. They also aren't being utilized for any aerodynamic benefit as they apparently exit out the top of the engine cover, ahead of the windscreen. So this leads me to believe that the exhaust flow from a turbo perhaps isn't that useful aerodynamically. I also understand that the driver is much further back in the chassis than I would have guessed, very close to the rear wheel.



A lot of people doubt the rear wing delete. I get it, we're so used to the current paradigm as it's what, 45 years old? But remember that aero balance follows weight distribution, I can't stress this more; this is pure physics and car setup basics. So by piling the front with weight there becomes less of a need for rear aero balance, and therefore you can begin to consider new options regarding the rear wing. But the removal of the rear wing is more about eliminating unneeded drag. Yes, the rear wing is the most efficient aero device on the car, something on the order of better than 10:1 (compared to a total car L/D of approaching 6:1 at Le Mans). And yes, the rear wing also produces on the order of 20% of the car's total downforce. But the list is precious short for items that can reduce drag so dramatically, around 8% of total drag. And hence eliminating the rear wing is not nearly as counter intuitive as it might seem. And there's been a bit of back and forth about the legality; frankly I've looked at the regulations myself and see nothing that makes a rear wing mandatory. However, in the event it is deemed a necessity, it's easy to imagine a very short chord vestigial rear wing, aerodynamically invisible, being added simply as a rules work around.



And drag reduction isn't limited to the removal of the rear wing. At the rear we can surmise with some confidence that the rear is narrower than the front, 1800 mm vs. 1900 mm. As mentioned previously, it makes sense. But in reducing the rear overall width it becomes apparent that Nissan will not be able to utilize the maximum allowed 14” wide rear tires if they want to maintain the maximum allowed tunnel width of 1100 mm. When you reduce the rear car width from 1900 mm to 1800 mm, you're left with a space that a 12” tire will fit while maintaining the same relationship between the inboard face of the tire and the outer wall of the underfloor as a 14” wide tire (the regulated maximum) out to the 1900 mm max car width. A 13” wide tire will go into this space too, but it begins to encroach heavily on the outer wall of the underfloor, with negative implications via tire wake and underfloor interactions. But if 12” or 13” wide, that's another small chipping away of total drag. However other factors (see below) might indeed see Nissan retain 14” wide rears in lieu of traction desires and in that case they would have to opt for less than the 1100 mm max tunnel exit (the regulation is 1100 mm max tunnel exit width, 1000 mm minimum).



But wait, there's more! I understand that the GT-R LM has a unique rear half shaft arrangement, in that the half shaft is not on-center to the upright, and drop gears, located in the uprights, are utilized for final power transmission to the rear tires. I've never been 100% sure on whether or not the rumor of smaller sized tires at the rear meant narrower width or smaller diameter. I've somewhat moved away from thinking narrower width. And the details regarding the drop gears and half-shafts leads me to smaller diameter. Because as wheel diameter gets smaller, the center point of the hub begins to lower to a point where, combined with a narrower rear end, the half shaft angle starts to get sketchy. The drop gears are used in order to actually reduce what the drive shaft angle might have been, all with the idea of letting the CV joints actually survive. But why all this hoop jumping for smaller diameter tires? Well the rear wheel arches are responsible for between 5 and 8% of total car drag. If you can reduce rear tire height, you can surmise you can chip away at some of that 5-8%.



Further evidence of extreme drag reduction as being a primary design principle is that I was told the top speed projections Nissan are using in their lap simulations are "mental." It would seem Nissan is concentrating on the extreme end of a fast lap time at Le Mans (approaching it from pure drag reduction), and have forged into an area that no one has gone in 60 years. The question remains whether they've strayed too far off the curve that defines lap times at Le Mans.



I've finally been able to confirm that total system horsepower figure. Ready for this? I've been told, from reliable sources, that the Nissan GT-R LM's total system horsepower is a conservative 2000. Yes, that's what you read. However, while these numbers certainly grab your attention, they really are relative to the storage capacity and the harvesting and release strategy, of which we know nothing about at the moment. I can't even assume which Release Energy class Nissan are running in. So while this number is quite fantastic, ultimately it's a little meaningless without context. Mulsanne's Corner Book Store

A selection of sports car related DVDs and books, with a technical slant.

