The Heterodox GT-R LM Nismo Endurance Racer

We can all thank  the US military and the need for cross wind landings for the begnnings of Bill Millken's  work on tyre and vehicle dynamics which has led to so much modern racing car dynamics.

 

Thye paid for a big rig to measure lateral tyre forces at varying angles and cambers. .Se page 428 of his book

NHRA tried to push fwd drag cars a few years ago, it is entirely possible.

 

FWD drag racing is massively popular in some areas of the US and other parts of the world. I know a lot of you will think drag racing a poor example, but think of the issues?

 

You have to apply that poiwer through a fairly conventional tranny, using a diff and driveshafts that are steering too,

 

You have no advantage in weight really other than having a reverse situaiton to say a Beetle in that the engine is over the wheels, a fwd drag car has nothing in it behind the driver.

 

Torque steer, can yu imagine it? 

 

The works Chevy Cobalt fwd Pro drag car had 1600hp, it was a bit of a cheat becaise the engine was Audi like, right up front, longitudinal, with a direct drive box behind it so the fwd was still within the silhouette, but it was fwd, it steered the front wheels.

 

Not a similar comparison I know but you get hte point, high power can work in fwd cars.

 

And the numbers?  This thing was capable of just under 7 second quarter miles.

Front Drive Pro Stockers seem to crash a lot! Quite quick but I ask WHY?

...but I ask WHY?

I ask why not.

I am struggling to think of any FWD road or competition car with more than about 300bhp.  Why do Nissan think they can put down 550+ bhp?  It seems a recipe for poor handling, difficult cornering, broken CV joints and high tyre wear.

 

 

One from a long time ago at Indy:  the Kurtis-Novi from 1946 and its 1947 built sister car. the original Novi for many. Front wheel drive, no differential (!) 500 hp from a centrifugally supercharged 3 liter V8, ran from 1946 till 1953 at Indy, failed to qualify in '54 and '55. Track record holder from 1946 til 1950 (Ralp Hepburn), during one week in 1951 (Duke Nalon on Pole day, records bettered one week later) and from 1952 til 1954 (Chet MIller). One of the two chassis, coincidentally the car in wich both Hepburn and Miller set their track records killed both the track record holders.

 

I mentioned it briefly in an internet piece over here, it also contains a few pictures I made of the cars.

 

http://8w.forix.com/...forerunner.html

 

 

 

 

Henri

Back again,

 

An interesting thought about the Nissan and the ability to transmit 550 hp trhough the front wheels and also use these wheels for steering,

 

On the Novi I mentioned, the same happened and the car wore out its tires rapidly. But that was also because of the actual car being rather heavy, even compared with its opponents and the supercharged engine demanded tremendous amounts of fuel. From 1948 on the car had a fuel tank of 435 (!!!!) liter in the tail! Thus specially when still heavy on fuel the weight balance was off and the balance of that car changed dramatically during a stint from full to empty tank.

 

Making prediction for the Nissan will be very difficult because we have no ideas how well the current day tires can deal with the stress, there is also the advantage of much more sophisitcated suspension technology and differential etc. The Novi was very basic in all of that.

 

People with knowledge about Indy probably know about the following I like to tell, for those who are not familiar with the story yet.

During the days of the Novis, there was also a team ran by Lou Moore, he had built frontdrive cars too, almost shrinked down versions of the Novi. The Novi and the Moore carse used the same gearbox technology to enable the engine sitting as low in the car as possible. Moore however used inboard front brakes to reduce unsprung weight and thus tire wear. Moore was however also clever enough to understand that with too much power he would shred his tires in too short a time. So he developed a strategy to keep his cars as light as possible, going so far that he even sacrificed power by using high octane gasoline for fuel fo his high compression Offenhauser engines, initially his cars had a mere 270 or so hp but being featherlight and requiring a small amount of fuel he developed the strategy to have his cars making a pitstop only once during the race for fuel and fresh tires while everyone else stopped at least twice. And pitstops took ages at that time.....

 

Moore's cars were the Blue Crown Specials, the two cars built came home 1st and 2nd in both 1947 and 1948 and were running 1-2 in 1949 after 193 laps and had Mauri Rose followed  team orders to settle for second instead of hunting down his teammate in his desier to win three races in a row, the cars would have scored three double victories in the fisrst three years of their existance instead of 3 first and 2 second places.

 

Message within this piece of history:  There has been a case of a carefully thought over frontdriven concept in a major race which had been carried out so meticulously that it simply had to work and thus paid of handsomely. Maybe the Nissan will be the next such a project?

 

 

Henri

Thank you for that, Henri.

 

However, I think there may be a difference between Indy - a large oval track where little steering lock is needed and there are no tight, slow corners to negotiate - and somewhere like Le Mans.  It is round corners like Arnage where a high powered FWD car might look a bit ungainly.  A driver in a conventional car turns in, hits the apex and stands on the throttle.  Will the Nissan driver be able to do any of those things, or will it be an ugly scrabble? 

 

Time will tell.

Edited by BRG, 26 February 2015 - 19:12.

They'll feed in the power and keep the tires under them, like any half decent racing driver will.

But if that means they can only use, say, half power compared to the others who are using 75 or 80% immediately, won't they be a lot slower onto the next straight?  And so slower on the lap?

Edited by BRG, 26 February 2015 - 20:01.

Depends how the thing is designed/setup. If they accept that cornering is always inherently compromised during an endurance race, maybe it's optimised to go like a bad stench down the straight.

That has to be it i think. That and recovery being superior. Making it run long and fast on the straights.

Thank you for that, Henri.

 

However, I think there may be a difference between Indy - a large oval track where little steering lock is needed and there are no tight, slow corners to negotiate - and somewhere like Le Mans.  It is round corners like Arnage where a high powered FWD car might look a bit ungainly.  A driver in a conventional car turns in, hits the apex and stands on the throttle.  Will the Nissan driver be able to do any of those things, or will it be an ugly scrabble? 

 

Time will tell.

Thanks, I only listed the Novi and Blue Crown exploits as an example that thinking out of the box could lead to. Disaster and success......

 

Looking to it rationally, I also wonder how that Nissan can work properly in the curvy part of the track.

 

Difference between highspeed Indy back then with the technology of then and Le Mans nowadays in an era dictated by aero is indeed next to impossible.

 

Imagine what would be possible with that Nissan iIf the Hunaudiéres was still a 6.5 km long straight....

 

I stll can't say I like the car, it's so butt ugly that I don't wanna think about what will happen should it be a success and we're gonna see a field full of such pain-to-the-eye Specials. But as a manner of thinking, the concept behind it and the technological challenge behind it, that one car fascinates me more than the entire F1 season combined.

 

 

Henri

One thing with heterodox chassis designs is the demands necessarily put on the tire supplier.  Safe to assume the tires fitted will be far less optimized for the design than the tires fitted to the competitors' cars, as those are operating in a far better understood performance envelope.  How many resources will the tire supplier pour into developing the tires on a separate development cul de sac that may not give a lot of knowledge that crosses over to conventional chassis tire design?  And what if the tire supplier decides at some point they've pumped enough money into the development already or even wants out? There's hardly any guarantee that another supplier will take on the project. 

They may if you tag your entire production line to the supplier. Sure, maybe the fruits of the race tire development are negative, but in exchange for outfitting all Nissan product sold in a given region, or globally, you suddenly wield a very large carrot.

You can pay a tire supplier to build a tire for you. Or you can design the car around a common tire. Michelin were talking about being able to layup tires as one-offs, not too sure if that really happened.

I can't see the financial case for a tire company to produce special tires for sports prototype racing. While I appreciate that some tire companies do so, it still does not make sense from a business standpoint. The television coverage of sports prototype racing is limited. But TV coverage of F1 or NASCAR racing is quite substantial, so a business case for companies making race tires for these series makes sense.

 

And then there is the situation with NASA giving Michelin a multi-million dollar contract to design, test, tool and manufacture a couple dozen or so tires for the US space shuttle program each year. Each of the six tires were only used for a single landing of the space shuttle. And the MLG tires cost over $6K each.

Henry do not worry. I believe the engine up front is due to harvesting rules. Michelin made one ofs for the Peugeot 208 T16 Pikes peak car.

Edited by MatsNorway, 01 March 2015 - 10:19.

While I accept that frond drive has limitations when it comes to corner exit with high power to weight ratios, I can't believe what I am hearing about problems with the twisty bits.  Is it really that long ago that minis were quicker through tight sections than any rear driver?

 

I repeat what I said earlier. Front tyres are the most likely Achilles heel for the Nissan. Corner exit performance will depend a lot on electric drive to the rear wheels (or not).

As far as the tire being for fit the job, I think they will probably be in a better position than their competition. It's quite possible that there is a single construction (at the very least a single philosophy) used for all of the cars with a similar architecture. The Nissan tires will be bespoke and very much tailored to the handling characteristics they are dealing with.

As far as power delivery goes, everyone is stuck on the fact that the gas engine is plumbed through the front tires and ignoring the fact that it is really an all wheel drive car with another 700 horsepower coming from the electric motors and plumbed to whatever corner is most beneficial.

Having said all this, the word around the campfire is that they are struggling. With what I don't know. When you consider how different and complex this car is and the fact that it is a multi-year program, it's not really such a big surprise.

Where did you see that it has any power going to the rear wheels? Especially 700hp! That would be rather silly considering the rear tires are narrower than the fronts.

http://blackflag.jal...50-h-1683150735

This says the thing has 1250 hp, so by my math, I'm seeing 700 hp electrically. It also says the ERS can deliver power to the rear tires. I never said it was putting 700 hp to the rears, but there is 700 that can be distributed among all 4 corners. I suppose how I wrote it there could be confusion that it was all to the rear. Maybe it is, but I sure as hell don't know.

Keep in mind, on initial throttle application out of a low speed corner, you might only want 50-100 hp put through the rears. You'll put whatever the car will accept. As the car straightens up you'll feed in the rest wherever you can. The big power dump comes initially to get the car to accelerate as quickly as possible. At the end of the straight you'll be only on the gas engine.

Is it really that long ago that minis were quicker through tight sections than any rear driver?

They were far smaller than the RWD cars and had a better power to weight ratio.  Once a similarly small and light RWD car came along - the Hillman Imp - it thrashed the Mini despite giving away a bunch of ccs and bhps.  Bill McGovern - British Saloon Car Champion 1970, 1971, 1972 in an Imp.

They were far smaller than the RWD cars and had a better power to weight ratio. Once a similarly small and light RWD car came along - the Hillman Imp - it thrashed the Mini despite giving away a bunch of ccs and bhps. Bill McGovern - British Saloon Car Champion 1970, 1971, 1972 in an Imp.

Well, there we go. Hillman Imps were faster than Minis 40-some years ago. Therefore, the Nissan LMP is garbage.

It's truly difficult to argue with this logic.

I'd like to know the relative difference of the front and rear wheel contact patch areas, the F/R static weight bias and where the aero CoP at speed is F/R relative to the center of Mass. It seems like it might be difficult to balance everything out dynamically and have the aero CoP rearward enough to give good high speed stability.  But I'm sure they have considered all that. 

Well, there we go. Hillman Imps were faster than Minis 40-some years ago. Therefore, the Nissan LMP is garbage.

It's truly difficult to argue with this logic.

Don't you know? Everything was better 40 years ago. Just ask Lee ;)

Good insight, desmo. Contact patch and aero distribution w.r.t. weight distribution is very important. It's one of those base design considerations which has, no doubt, been a big part of this car's design.

In general, I shoot to have my weight distribution mirror my contact patch distribution within a couple percent. In the best scenario I'll end up with the static weight distribution a little forward of the contract patch distribution, but it'll be close. It's very tough to do on some cars.

Aero c.o.p. is easier to shift fore-aft. To keep the car stable you want the aero distribution to be a couple percent aft of the mass. The actual amount aft it has to be will be determined by the watch. I've had many cars which the drivers like better with more front aero, but, maybe surprisingly, the car is actually faster with more rear. The additional stability and braking performance will often outweigh a more neutral mid-corner balance.

My guess is that the LMP rules make it relatively easy to make front downforce and rear is the limiting factor. If so, a heavily forward front weight bias will mean they can run a ton of front aero while still being somewhat to the rear percentage wise in comparison to the c.g. If my assumptions are correct, this will mean good total downforce in comparison to a rear engined car. It will probably also mean a nose which is very sensitive to pitch & ride height. It's rare to get one (high total numbers) without the other (running sensitivities).

Is traction control permitted in LMP1?

 

I suppose the Nissan could be in dire need for that!

 

Henri

Traction control? It's really more of a stability control. Yes, it controls wheelspin, but it's _so much_ more than that.

If each wheel has its own motor (I'm thinking the rears put perhaps the fronts as well) you could, I expect, do a lot of SC stuff if you can successfully close the control loop.  Imagine having active or semi-active suspension and four independently powerable wheels all working in coordination, you could in theory have a near perfect set-up for every corner/braking/accel zone--no compromises. Or make what should be a dynamically unstable chassis quite driveable.

 

Do drivers report front/rear aero bias as simple understeer/oversteer and how do you untangle aero from mechanical u/o steer when trying to get a set-up? Seems like a rear aero balance should *feel* similar to mechanical US but very speed variable. 

Torque vectoring if permitted, offeres a huge advantage in yaw control but also in ultimate grip level. 4 wheel torque vectoring is the only way to have all 4 tyres operating at their optimum traction ellipse vector angle.

 

Regarding yaw control, it is desirable to have a basic suspension setup which is stable and optimised for grip in steady state cornering. This usually means a chassis that understeers on turn-in and probably elsewhere in the corner. Adding in the torque vectoring allows the cornering attitude to be adjusted at will and understeering characteristics dialled out.

 

Using torque vectoring to add stability is the normal mode for road cars (ASC) to protect drivers from themselves. It would be interesting to see it implemented on a race car to compensate for unstable regions of the operating envelope.

I imagine any loss in exit traction and resulting loss in lap time will be offset somewhat by;

 

- The extra energy that can be harvested under braking due to the wider front tyres and front weight bias, a harvesting double whammy.

- This extra energy can then be re-deployed once the car has accelerated beyond it's traction limited speed to reach it's no doubt substantial top speed sooner.

 

The rules are written to allow/reward this thinking. Well done the ACO/WEC

 

At Le Mans this makes a lot of sense. There are 5 huge straight line (more or less) stops and another 2/3 medium stops on a lap of Le Mans yet only really two low speed traction zones out of Arnage and Mulsanne which both happen to be straight line traction zones further negating the FWD torquesteer disadvantage. The Porsche curves will be at high speed and have plenty downforce at exit. Not much steering angle is used in the chicanes, even those at the S/F. The only possible traction limited exit I foresee the Nismo losing out noticeably is the tricky camberless exit onto the first long straight at Tertre Rouge.

 

Silverstone might be a different story though, a track where the long sweeping traction limited exits outnumber the big stops.

 

Will be watching with interest!

There is one other thing that concerns me a bit.

 

the WSC championship has several races, of which Le Mans is only one

 

Audi, Toyota and Porsche appear to have given Le Mans priority, yet still create a car that can compete competitive as well just about anywhere else.

The Nissan however appears to me as being designed with Le Mans only in mind and to a much more extreme level then what the opponents did, Up to a point that is seems to b a car that won't work very well at some, if not most of the other tracks.

But who cares. Le Mans is the one prize you want. Even in the last 10 years there have been WSC titles lost by Audi (which ones?) but more likely that most of us know which Le Mans the didn't win because of remembering the ones they did win!

Peugeot had done fairly well over time in WSC but we remember the failures at Le Mans better. So what Nissan does makes sense.

 

If it pays off, won't that not undermine the status of the WSC and make it a championshop of little to no value other then that Le Mans is part of it?

Won't it not lead to similar strategies by other constructors, and in the most extreme case? factories spending millions on two types of cars: one for Le Mans and events on tracks that resemble Le Mans the best of all and another car for the other tracks?

So we gonna see what we saw in the 50's and 60's in the US Champ car series: A team running/needing two entirely different cars: one front engined dirt-track car and a car for the paved oval of Indy, i.e. a Roadster in the 50's and a rear engined car in the second half of the 60's.

 

Such a scenario could be a costly affair, even more costly than running one type of car as is been done now.

 

 

 

Henri

If you'd like to see and hear it go through the Sebring hairpin...

 

http://www.motorspor...at-sebring/?s=2

Looks slow.

 

Looks slow.

It looks slow on the corner entry, but pretty damn quick once it straightens up.

Very low rpm on exit. Either it is not at 10/10 or there is ample electric power available out of slow corners. (Especially if electric power is available to the rears.)

In the photos I've seen from Texas  the rear wheels don't appear to me to be powered even though driveshafts are fitted.  The rear suspension arms are *short* and there are two hydraulic lines running to each damper.   

I imagine any loss in exit traction and resulting loss in lap time will be offset somewhat by;

 

- The extra energy that can be harvested under braking due to the wider front tyres and front weight bias, a harvesting double whammy.

- This extra energy can then be re-deployed once the car has accelerated beyond it's traction limited speed to reach it's no doubt substantial top speed sooner.

 

The rules are written to allow/reward this thinking. Well done the ACO/WEC

 

At Le Mans this makes a lot of sense. There are 5 huge straight line (more or less) stops and another 2/3 medium stops on a lap of Le Mans yet only really two low speed traction zones out of Arnage and Mulsanne which both happen to be straight line traction zones further negating the FWD torquesteer disadvantage. The Porsche curves will be at high speed and have plenty downforce at exit. Not much steering angle is used in the chicanes, even those at the S/F. The only possible traction limited exit I foresee the Nismo losing out noticeably is the tricky camberless exit onto the first long straight at Tertre Rouge.

 

Silverstone might be a different story though, a track where the long sweeping traction limited exits outnumber the big stops.

 

Will be watching with interest!

Good perspective!

Even at 8MJ the hybrid energy is only about 5% of the fuel energy per lap.

Given the limited fuel and Hybrid energy per lap, the lowest drag car to finish will win Le Mans.

Nissan might have the edge on that.  How close they are a Silverstone and pa will be a good clue.

If the Hybrid energy was made unlimited it would really open up design possibilities and make for much more dramatic acceleration.

The Koenigsegg Regera is a good example.  Direct drive transmission.  Hybrid energy would have to be at least 40MJ to make this competative.
http://www.electric-...00-hp-plug.html
 

Even at 8MJ the hybrid energy is only about 5% of the fuel energy per lap.
 

Don't forget that only 30% of the fuel energy becomes mechanical work so 5% extra is not chicken feed.

Looks slow.

 

If you've ever been to Sebring you'd know that it is one of the worst tracks there is. The track surface is full of bumps and ledges that cause a race car with a stiff suspension to lose traction. And when it rains, which it often does at Sebring, the poor drainage of the track creates huge pools of water at every low point on the circuit.

Nice change from the rather silly ratio inflation we are being dealt in auto gearboxes today.  Has anyone done the ten speed 'box yet?  It's like bicycles and rear sprockets--it becomes more marketing than engineering.

Here's the rear suspension, with the short arms and hydraulic lines running to the dampers.

 

 

No obvious ARB in sight, maybe done hydraulically?  Also the mounting of the coilover is strange to me, with the buckling load in that arm, and then the threaded drop link for ride hight adjustment I guess.  Look how small the brake disc is.

Edited by jpf, 05 March 2015 - 14:49.

Very low rpm on exit. Either it is not at 10/10 or there is ample electric power available out of slow corners. (Especially if electric power is available to the rears.)

 

I'ts confirmed by Autosport that they weren't using the rear hybrid system.

 

http://www.autosport...9049.1390166791

If you've ever been to Sebring you'd know that it is one of the worst tracks there is. 

 

It was a jest of course -  mocking those who announce something 'looks fast' based on a single picture.

 

However, just at the very end of the clip, we see an Audi going through the corners noticeably faster.  But if they weren't using any rear hybrid power, it isn't a fair comparison.  So we must wait and see...

I'ts confirmed by Autosport that they weren't using the rear hybrid system.

 

http://www.autosport...9049.1390166791

Thanks. So even less reason to have the revs up - IC and electric power both headed for the same grip-limited axle.

In the photos I've seen from Texas  the rear wheels don't appear to me to be powered even though driveshafts are fitted.  The rear suspension arms are *short* and there are two hydraulic lines running to each damper.

How would you know if the rear wheels are powered from photos? The rear drivetrain is inside the bodywork up until it reaches the driveshafts.

Do the hydraulic lines simply run to accumulators or reservoirs or do they interconnect with other corners or a control system?

Good perspective!

Even at 8MJ the hybrid energy is only about 5% of the fuel energy per lap.

Given the limited fuel and Hybrid energy per lap, the lowest drag car to finish will win Le Mans.

Nissan might have the edge on that.  How close they are a Silverstone and pa will be a good clue.

If the Hybrid energy was made unlimited it would really open up design possibilities and make for much more dramatic acceleration.

The Koenigsegg Regera is a good example.  Direct drive transmission.  Hybrid energy would have to be at least 40MJ to make this competative.
http://www.electric-...00-hp-plug.html
 

 

Yes, if they are close to the pace at Silverstone I'll be putting money on for Le Mans. If they only come 5th at Silverstone that will lengthen the odds too as they will look uncompetitive to the layman. Insider trading! 

 

The Regera is freaking awesome. I love the design, it's dramatic but clean also, something the McLaren P1 most certainly isn't to my trained designer's eye. Don't know if it is intentional but I love the XJ220 esque rear end!

 

The fluid lines attached to the rear dampener are far too small to transmit any significant amount of power by hydraulic pressure.

 

I saw this picture, and what caught my eye was the location of the transmission clutch. It's way out front. Is this done for easy service access during endurance races?

 

Edited by bigleagueslider, 07 March 2015 - 04:53.

The fluid lines attached to the rear dampener are far too small to transmit any significant amount of power by hydraulic pressure.

 

I saw this picture, and what caught my eye was the location of the transmission clutch. It's way out front. Is this done for easy service access during endurance races?

 

 

 

More likely to help put the weight as far forward as possible. With FWD to get the power down you put the weight as far forward as legally allowed. Look at pictures of FWD dragsters.

What sort of sensor would be used like that on the ride height drop link? Strain gauge maybe? There's a sensor hidden on the drop link under some heat shrink, another snaking down into the upright, and a 3rd sensor that looks like perhaps a hall effect  bolted on above that.