| mav1178 |
02-02-2015 11:25 AM |
Given that they want to compete at Le Mans, and given the current LMP1-H rules... how would one go about creating a car that is competitive against Audi/Porsche/Toyota, who all (more or less) have the EXACT SAME CAR?
Given that no one has been able to realistic get a running car in the 8MJ hybrid class, and since aero is such a big part of Le Mans... why not?
I really enjoy reading Mike Fuller's Mulsanne's Corner.
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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.
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 wheel centerline and hang ahead of 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. The suspension hangs off the gearbox/bellhousing as well and the ICE power 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. Does make you wonder what that will do to driver vision when driving at night.
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). All the air scooped up at the front by the front splitter/diffuser exhausts into tunnels running either side of the monocoque, down the car's wheelbase, and out the back of the car into the low pressure area in the rear of the car. 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.
Recall the drop gear uprights? It all comes to play in the rear; the half shafts are raised to clear the tunnels Nissan GT-R LMP1, serrated strakeand 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.
And it would seem the primary purpose of the full length duct is front diffuser activation as 100% of the heated radiator air exits ahead of the front wheel centerline. However, it appears the intercoolers are tucked in very close and towards the rear end of the engine so there's certainly a cooling benefit with the heated air from the intercoolers being drawn out the rear of the car as well.
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. 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. Strike two for me. But the fronts are 13" wide and only 9" wide 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, so 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. That's the third thing I was wrong about.
Yes, the Nissan has a rear wing. It is a tick smaller in chord than one might expect. 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 will have to be reduced, thus the rear wing, while much more substantial than "vestigial", is reduced. In the end this was my unintended contribution to the, "wild rumors." Though it would have been interesting. Fourth, and it was a biggee.
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 will admit 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 distrubution, it all makes elegant sense in the end.
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