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.