[WEC 2015]Nissan GT-R LM NISMO

[machin]

This link has (a little bit) of information on the fact that really the car is AWD and not FWD...

http://www.roadandtrack.com/motorsports ... en-bowlby/

And with the very forward biased weight distribution it won't need that much power going to the rear, so I think slow speed acceleration should be fine... If the rear electric drive is working...

For me the question is whether they can generate enough front downforce... The front bias mass needs more front downforce than a "conventional" LMP, and with the front engine etc they appear to have less room to play with... I'd love to see a picture showing how the air enters the "through-tunnels" because the space beside the engine looks quite congested...???

[Tim.Wright]

I'd say that he has probably learned a lot from the DW experiment and might have a different point of view now.

Looking at the DW or Zeod or whatever its called now at Daytona just recently it looked unstable everywhere, corner entry, corner exit, under brakes...

I'd have to say that he now has an experience regarding extreme mass distributions and attempting to match tyres to it that practically no-one else in the world have.

I'd be interested to hear what his opinion on this is now.

[langwadt]

with the driver sat so far back i'm sure the visibility over the front wheels would be an issue. straight ahead and to each side should be fine, but spotting and finding apexes could be interesting, not to mention other cars.

doesn't look any worse than the Panoz. I wonder if those exhaust will be an issue at Le Mans, I doubt looking into two blow torches will do anything good for your night vision

[Jersey Tom]

I'd be interested to hear what his opinion on this is now.

Probably something to the effect of, "Wow I'm not doing something that silly again."

[lkocev]

Might this design have some performance potential? I thought that the aero balance of LMP's was quite 'forward'. Anything to do with sports or racing, sounds strange to me if it is front drive, but I guess if the grip is available, then perhaps its worth a shot. I would expect difficulties managing tire wear, there will be quite a lot of energy going those front wheels.

[RacingManiac]

This link has (a little bit) of information on the fact that really the car is AWD and not FWD...

http://www.roadandtrack.com/motorsports ... en-bowlby/

And with the very forward biased weight distribution it won't need that much power going to the rear, so I think slow speed acceleration should be fine... If the rear electric drive is working...

For me the question is whether they can generate enough front downforce... The front bias mass needs more front downforce than a "conventional" LMP, and with the front engine etc they appear to have less room to play with... I'd love to see a picture showing how the air enters the "through-tunnels" because the space beside the engine looks quite congested...???

The air comes in from the bottom, its the exit flow of the front diffuser....instead of out the side like all the other car, it goes out the back, and option not otherwise available to anything else.

Also the hybrid drive in this thing is not electrical, the flywheel is mechanically driven to the drivetrain.

[Scania]

This link has (a little bit) of information on the fact that really the car is AWD and not FWD...

http://www.roadandtrack.com/motorsports ... en-bowlby/

And with the very forward biased weight distribution it won't need that much power going to the rear, so I think slow speed acceleration should be fine... If the rear electric drive is working...

For me the question is whether they can generate enough front downforce... The front bias mass needs more front downforce than a "conventional" LMP, and with the front engine etc they appear to have less room to play with... I'd love to see a picture showing how the air enters the "through-tunnels" because the space beside the engine looks quite congested...???

It returns its energy to the front wheels through the same shaft that runs through the V6's 60-degree engine V, and can send the rest, if the team decides to use AWD, to the rear through a long driveshaft beneath the tub that connects to a differential which then feeds the rear wheels through a complex system of secondary driveshafts and outboard gearboxes.

looks like AWD is an option?

[machin]

the flywheel is mechanically driven to the drivetrain.

Here's another question then.. the spec says the flywheel KERS can drive either the front or rear tyres... If the flywheel KERS connects to the front tyres, and so does the IC engine, does that mean that the IC engine can drive the rears via the flywheel KERS, or is there something that stops power transfer back that way...?

[RacingManiac]

I don't think if the system is connected there will be anything to stop it. I'd be curious if the rule has anything to stop that from happening. I really have no idea how integrated everything will be. I think at some point one of the rumor was there might be 2 flywheels, one for the front system the other the back. But Nissan hasn't been very clear on that. IIRC, per rule they can indeed use 2 ERS on a car, Toyota currently has 2 sets of electrical KERS running off capacitors(front +rear), Porsche has a ERS-H off the engine(not connected to the turbo) and a front KERS, feeding to battery pack. Audi has a KERS with flywheel storage for the front only since they abandoned rear ERS-H last year. In Porsche's case since they can only use the KERS to drive the front wheels, that power can only go to the front, and the storage from the engine is really just scavanging waste. Audi doesn't have anything outside of front KERS so really they are not on the same boat. Toyota currently is the only one I think can apply drive with KERS to both axle. Are they capable of doing that pending on the need and decide on where that power go to? No idea. Nissan placed the flywheel behind the engine even for the front unit because of packaging I think, but whether if its somehow directly connected to the rear system I think remain to be seen...I'd also imagine they would limit how much the rear can be driven given the tire size and probably torque capacity of the drivetrain parts used out back.

I am still not entirely convinced on the mechanical based system. I can see the advantage of perhaps less losses compare to a electrical to mechanical type like the Audi system, but in a car that seems to be very cramp on packaging space, you'd think wires are easier to deal with than axles and gearboxes...

[Artur Craft]

Much more photos with good details at sight can be accessed(4928x3280 resolution) in:
https://www.flickr.com/photos/nissan-racing/

[DaveKillens]

I'm going to borrow this picture from Artur Craft because it ties together what I believe is happening.


Let us look at the V-6 and the transmission. Hmm, nice example of 3-D printing for that transmission mockup. Anyheww, the V-6 power is transmitted by the traditional means of the crankshaft connected to the transmission. This transmission is also coupled to the flybrid mounted in the middle and near the drivers via a driveshaft that runs through the V of the ICE engine. There is a driveshaft that exits the transmission down low and travels to the rear, connecting to the rear differential mounted higher than normal practice. The dear driveshafts travel above the ducting, go through gear that deliver the torque down at the rear wheels.



The transmission allocates torque front to rear or to the flybrid depending on the requirements of the moment, braking and charging, low speed acceleration, or high speed acceleration. The flybrid adds it's contribution when and where that too is required. All the magic happens inside that transmission.

The second big question is "how are they going to find front downforce in a vehicle with so much mass located so far forward"? The answer is a super-efficient front diffuser. The picture below is of a different type, but it illustrates some of the basics.



In the above picture the front diffuser air is dumped into the front wheel wells or out the sides. But in the case of the Nissan, it goes through very clean and efficient ducting all the way to the rear. There is a very good reason why the V-6 exhaust and turbos are located so high, to make room for the ducting.



And since that rear ducting is of a large cross section and at the very rear of the car, it acts a little like the famous fan from the Brabham BT46B, providing very low pressure to extract air from the front diffuser.

This entire vehicle is built around two basic concepts, extremely low drag of the externals of the car, and super-efficient diffusers. The engine and transmission is located at the front to optimize the diffusers, there is basically nothing behind the driver but bodywork, a driveshaft and it's associated mechanicals, and the diffusers.

Fans at LeMans, anywhere near the exit of any corner leading to a straight will really enjoy themselves, watching an endurance version of a top fuel dragster light it up and scorch the pavement. Once the car gets going fast enough for the front diffuser to really stick the tires to the pavement, WOW.

[machin]

Hhhmm... I'm not entirely convinced by the "super efficient front diffuser"....

The reason I say that is that other LMP1's (the Audi at least) features what is effectively a two element front wing between the front wheel fenders, as seen in the image below:-



It is not clear from the photos I've seen of the Nissan whether it has this dual element front wing (but I think not)

Also the Audi clearly has a very unobstructed route from the front splitter/wing to the side vents (see photo below).... whereas the front end of the Nissan looks quite congested in the area where the tunnels start.... although maybe I've just not seen the right photos???

[RacingManiac]

Toyota also chose to do without the adjustable flaps...so its not the sole solution. It was allowed last year for the first time.

Everything you see in the engine pics are above where the floor of the Nissan. I am assuming there is an closeout for the mechanical bits where the front diffuser of the Nissan slopes over the actual floor of the car. The idea is not to dump the out flow of the front diffuser with the side and use that flow to fill the low pressure behind the car, and that low pressure also help sucking the flow out too. Which should help driving the diffuser and lower drag. At least they hope is what should happen.

Audi tried doing this before too with R15 back in 2009, but in their case it helped with more downforce but also added more drag, because they had also to divert the air around the mechanical bits out back...

[Blanchimont]

How is the air actually entering the tunnels?

Through the center part...


travelling backwards under the gearbox(in white), then to the sides of the gearbox and the engine and through the opening in the arc under at the front of the monocoque!?

[DaveKillens]

Diffusers deliver a great percentage of the total downforce for a Formula One, or LMP car. Wings are nice, but diffusers are much better. There is a very good reason why we endured the double diffuser and the blown diffuser, they can be a game-changer.

What is the best way to extract the air from the diffuser, dump it out the sides where there is some negative pressure but a lot of turbulence, or duct it to the very rear where it is subjected to very low air pressures?

The front end of the Nissan appears very ungainly and heavy, but it is basically just the V-6, turbos, radiators, transmission, and suspension.