Porsche accuses Nissan GT-R of cheating the "Ring":

[footie]

Originally Posted by bruce.augenstein@comcast.

Not to be unduly complimentary to him , but I believe footie's commentary in this string represents a paragon of good and informed sense.

Would that the SportAuto time be actually definitive. It's certainly of value, but as footie has pointed out, weather and track conditions vary enough so that one can't draw definitive conclusions from a given test against another test on another day. Horst soldiers on out there pretty much no matter the conditions (barring torrential rain or snow and ice), and this guarantees variations in observed times.

The definitive test would be the 'Ring version of Car & Driver's "Lightning Lap" wherein they rent a track and have at it with a bunch of cars - same day, same driver(s). Doubt if it will happen, but one can hope.

Bruce

Thanks for the compliment Bruce.

Here is my take on all the times that have been conducted on the ring by manufacturers. Take Nissan, Dodge and GM's quoted times on the ring, each on these manufacturers including all the others I haven't mentioned spend months and numerous thousands of miles testing and perfecting these cars, the laps which you see on Youtube and the like are the best they have achieved. No one knows what their average lap were like, only the one which gets the headlines.

Professional racers that happen to have lots of experience of the track are the best bet to get the most out of these cars when little opportunity is available to really get to know the cars. Sport Auto use Horst who is an accomplished racer but he is no where near as good as either the test drivers used by the manufacturers or top flight profession drivers. What we will get from the Sport Auto super test is a clip-pit of how the GTR performs on the ring on that day and with that driver. The Hockenhiem lap will give more insight as to how good the car grips and how hard it punches out of the corners.

P.S.
I hope they get a GTR with Dunlops to give it the best fighting chance.

[Robin_NL]

OK Horst von Saurma exit
Try fellow Dutchman Tom Coronel, the record-Viper ACR driver. No Fear. Pro driver. Nice guy. His father in law is ASCARI owner Klaas Zwart(born in the same town as I am, fyi LOL)

Or try Sabine Schmitz, Hans J Stuck, Stefan Roser(Ruf testdriver ), Michael Vergers or who else? Andy Priaulx!!!! Or Derek Bell.

[T Bone]

Originally Posted by bruce.augenstein@comcast.

Not to be unduly complimentary to him , but I believe footie's commentary in this string represents a paragon of good and informed sense.

Would that the SportAuto time be actually definitive. It's certainly of value, but as footie has pointed out, weather and track conditions vary enough so that one can't draw definitive conclusions from a given test against another test on another day. Horst soldiers on out there pretty much no matter the conditions (barring torrential rain or snow and ice), and this guarantees variations in observed times.

The definitive test would be the 'Ring version of Car & Driver's "Lightning Lap" wherein they rent a track and have at it with a bunch of cars - same day, same driver(s). Doubt if it will happen, but one can hope.

Bruce

Agreed that back to back on the same day same track would offer the best data....

But SportAuto seems to be the de facto standard, and clearly weather and other variables cannot be weeded out.....this is the randomness that needs to be accepted.

I believe the early M3 times were also done in the cold.

[bruce.augenstein@comcast.]

Originally Posted by T Bone

Agreed that back to back on the same day same track would offer the best data....

But SportAuto seems to be the de facto standard, and clearly weather and other variables cannot be weeded out.....this is the randomness that needs to be accepted...

Not by me. I personally feel more comfortable with the individual manufacturers and their hired guns. In general, my belief is that their times are very close to 100% of what an individual car can do. Those guys spend a ton of time on track with amazingly accomplished drivers, and a team of engineers making sure everything is up to snuff, carwise. They also spend enough time hanging around so that they can get a "good" day, weather and track wise. If they don't get that, they come back. Hence the 7:38 time with some wet corners dropping down to a 7:29, on another date with everything right.

Bruce

[bruce.augenstein@comcast.]

Originally Posted by devo

Didn't Nissan's man, Mizuno, go on record stating that a stock GTR has no chance of replicating a sub 7:30 N'ring time? I believe he said that a 7:44 was more likely attainable and that 7:5x's were the norm. Although, still and incredible car, it's far from the claimed time.

Finger pointing at Porsche is fine, but Nissan got caught lieing in my book. Nissan's aforementioned response is the dog wagging the tail.

Can you give me a pointer? I looked up a bunch of Mizuno's quotes, including one where he spoke of 7:40s and :50s. That was well before the 7:29 event, however (7:38 was the number at the time), and seemed as if the context was in terms of normal results, as opposed to absolute kamikaze laps under perfect conditions.

Where's the 7:29 reference by Mizuno?

Bruce

[T Bone]

Originally Posted by bruce.augenstein@comcast.

Not by me. I personally feel more comfortable with the individual manufacturers and their hired guns. In general, my belief is that their times are very close to 100% of what an individual car can do. Those guys spend a ton of time on track with amazingly accomplished drivers, and a team of engineers making sure everything is up to snuff, carwise. They also spend enough time hanging around so that they can get a "good" day, weather and track wise. If they don't get that, they come back. Hence the 7:38 time with some wet corners dropping down to a 7:29, on another date with everything right.

Bruce

Hired guns by the manufacturers is an arms race. In addition to hiring the best drivers and waiting for optimal conditions, I would be looking at production vehicles that have statistically significantly more power caused just by production variance.

Slight adjustments in suspension geometry, heat cycled rubber etc....

All-in-all, SportAuto is fair and comprehensive.

[footie]

TB,

Bruce is right, manufacturer times is exactly what the car is capable of achieving when everything clicks.

Sport Auto times are held on different dates, some in summer, some in winter, some on a totally dry track, some not so dry. If I remember correctly Horst only gets about 3 laps to get it right, this might prove more which car he feels most comfortable in and less about which car is the most capable.

The recent Autocar test held on the Isle of Man was an 'all the cars in one day' event with one driver. And knowing the Isle of Man TT course and the sections used it would present similar course conditions to how these cars would perform around the ring. In that particular test when the GTR's Japanese speed limiter didn't come into play the GTR destroyed the competition to such an extent that on the final high speed section where the GTR run most of it on it's limiter (113mph) against the R8 and Gallardo both sustaining 127mph and 130mph respectively the GTR still held the overall quickest time.

Not matter which way you look at it or slice it, the GTR is quite possibly the best handling real world supercar. And by this I mean on the public roads where there are bumps, humps and bad cambers.

God the more I defend the GTR's ring time the more I bloody want the thing.

[T Bone]

Originally Posted by footie

TB,

Bruce is right, manufacturer times is exactly what the car is capable of achieving when everything clicks.

Sport Auto times are held on different dates, some in summer, some in winter, some on a totally dry track, some not so dry. If I remember correctly Horst only gets about 3 laps to get it right, this might prove more which car he feels most comfortable in and less about which car is the most capable.

The recent Autocar test held on the Isle of Man was an 'all the cars in one day' event with one driver. And knowing the Isle of Man TT course and the sections used it would present similar course conditions to how these cars would perform around the ring. In that particular test when the GTR's Japanese speed limiter didn't come into play the GTR destroyed the competition to such an extent that on the final high speed section where the GTR run most of it on it's limiter (113mph) against the R8 and Gallardo both sustaining 127mph and 130mph respectively the GTR still held the overall quickest time.

Not matter which way you look at it or slice it, the GTR is quite possibly the best handling real world supercar. And by this I mean on the public roads where there are bumps, humps and bad cambers.

God the more I defend the GTR's ring time the more I bloody want the thing.

I understand Bruce's point but this methodology can be taken to extremes as you well know. I am just stating my preference.

Where you do think Sportauto will produce?

[M3WC]

Did you guys see C&D's lightening lap results?

Viper ACR won the LL3 class. Put the smack down on the GT-R, on a 4.2 mile road course.

4.2 miles ( 7 second gap):

Viper ACR - 2:48.6

GTR - 2:55.6



http://www.m3post.com/forums/showthread.php?t=175750



But there is only a ~7 second gap on the 12.9 mile Nurburgring????

[footie]

Unless I am way off on this one, the surface of this course bears no similarities with the ring and can't be used as a judgement or example of how the GTR's time can compare to that of the Viper. It looks as smooth as any other race track with run off areas and open plains to correct a possible mistake without the same fear of things going horribly wrong like is the case with the ring.

The only thing of interest I see in this test is the F430 Scud vs GTR times which are almost identical. Look at the exit speeds of each in relation to peak speeds, where to two exit at similar speeds the Ferrari peaks higher but on the most part the GTR exits quicker, again something I keep banging on about and is the most obvious reason for why the GTR is so quick on the ring and is able to still pull the big numbers on the straights as the other were capable of.

P.S.
I am a bit disappointed that the M3's best time was achieved in auto, I can't imagine how that should be possible and is a sorry state of affairs that it is in fact the case. Clearly BMW need to pull their finger out and fix the problem for our track based members.

[M3WC]

Originally Posted by footie

Unless I am way off on this one, the surface of this course bears no similarities with the ring and can't be used as a judgement or example of how the GTR's time can compare to that of the Viper. It looks as smooth as any other race track with run off areas and open plains to correct a possible mistake without the same fear of things going horribly wrong like is the case with the ring.

GT-R must be magical over the bumps. If you look at the C&D data, the Viper ACR's peak speed, cornering grip, exit speeds, and sector times kill the GT-R.

Wasn't really trying to compare the circuits. I was just impressed to see the Viper pull 7 full seconds on the GT-R on a 4.2 mile track. ACR is a track demon, for under $100,000.

If they would have included the ZR-1, I believe the GT-R would have moved to third in the class.

[footie]

Originally Posted by JetBlack5OC

GT-R must be magical over the bumps. If you look at the C&D data, the Viper ACR's peak speed, cornering grip, exit speeds, and sector times kill the GT-R.

Wasn't really trying to compare the circuits. I was just impressed to see the Viper pull 7 full seconds on the GT-R on a 4.2 mile track. ACR is a track demon, for under $100,000.

If they would have included the ZR-1, I believe the GT-R would have moved to third in the class.

Yes I really do think that the GTR is magical over the bumps and that is why the ACR doesn't pull a huge gap over the GTR on the ring.

It's the real world ability of the GTR that is so special.

[devo]

Originally Posted by bruce.augenstein@comcast.

Can you give me a pointer? I looked up a bunch of Mizuno's quotes, including one where he spoke of 7:40s and :50s. That was well before the 7:29 event, however (7:38 was the number at the time), and seemed as if the context was in terms of normal results, as opposed to absolute kamikaze laps under perfect conditions.

Where's the 7:29 reference by Mizuno?

Bruce

To be honest, I just re-read Mizuno's qoutes and, you're right , he did not mention the 7:29. only the 7:44 and 7:5xs. Maybe I read the information from other threads; at this point who knows, I'll just stick with the facts.

And, like I have previously said, I have no doubt that the GTR will best the current (MY2007-2009) turbo at the Ring and probably any other track. I just had doubts as to the 7:29. But, even if it's off by a few seconds, it really doesn't matter, it's still a very fast time.

I just prefer the turbo, even at the additional cost.

[bruce.augenstein@comcast.]

Originally Posted by devo

...I just prefer the turbo, even at the additional cost.

If some benefactor were to offer me a choice, I believe I'd even prefer a 911s, or even a base 911 over the Nissan. I have great admiration for the car, but no lust.

Bruce

[GnokGnik]

I hate the GT-R.

Hate it.

It defies what a fast car needs to be: light and powerful.

I have seen the thing parked next to a 525i and it completely dwarfs it.

[footie]

Originally Posted by bruce.augenstein@comcast.

If some benefactor were to offer me a choice, I believe I'd even prefer a 911s, or even a base 911 over the Nissan. I have great admiration for the car, but no lust.

Bruce

What you mean to say is it doesn't get you wet.

[swamp2]

Originally Posted by footie

There seems to be a small minority of people here who feel that weight and power are the only important factors to producing an incredible lap time on the ring.

There also seems to be a small minority who can not grasp a trend and prediction vs. an absolute statement. Power to weigh is THE MOST important factor in most performance categories. Obviously it is not the only one. No one EVER said that. It also varies much more than most other factors. I did the math for tires and for Cd x A, etc. Power to weight varies the most.

Originally Posted by footie

Oh, how wrong you are. Stating other models with more power and less weight does not make for the perfect track car or more importantly the perfect ring car. Maybe I throw one other car into the mix which either proves or disproves your opinion (it all depends on how you view things), the car in question is the Bugatti Veyron, it can out acceleration every other car and by quite some margin (a gap much greater than the 997tt or GT2 are capable of), it's got more power than any driver needs or knows what to do with and it actually can put almost all of it's power to the road almost all of the time and yet it's not the quickest, not by a long chalk.

Robin Hood listed all of these cars as examples, the Koenigsegg CCR did 7:34. GT2 7:33. Carrera GT 7:32. Talking about supercars with BHP and not that heavy. And his personal favourite: Ferrari 430 Scuderia, 1350kgs, 510BHP, semislick tyres: 7:39. How come the Veyron can't destroy all of these?

Simple, the car was neither design as an out and out racer, it's got too much power for the course in question and it's suspension can't cope with the type of road surface conditions that a track like the ring throws at it. What make you think that any of the others are any more suited to the circuit that the Veyron is?

You answered your own question: The Veyron was not designed at all as a track performer. It was designed to be a 1000+ hp acceleration monster that your grandmother can drive. GT-R was designed in a more impressive fashion; fast in the straights and turns and also something your grandmother can drive.

Originally Posted by footie

So as you see, your logic doesn't always work as more power and even perfect weight balance can't always produce the perfect lap time. I remember stating this when people were using mathematics and PTW to estimate lap times on the ring, there are too many factors involved to get the formula 100% correct, it may work for most of them but not all. In fact let me add another example of how far this thinking is out, the M3 and the M3CSL, each had pretty similar PTW but while one (M3) worked to the formula, the other (M3CSL) didn't and by some margin. Two cars which on the surface looked identical but were over 30 seconds apart.

Let me repeat...

There also seems to be a small minority who can not grasp a trend and prediction vs. an absolute statement. Power to weigh is THE MOST important factor in most performance categories. Obviously it is not the only one. No one EVER said that.

Also the power to weight advantage of the M3 CSL is HUGE, very close to 20% That was a really poor choice to make a case.

Originally Posted by footie

So what if the GTR is producing more power than it quotes, does that mean we will all demand them to reduce it to the quoted figures when the car is delivered, hell no. The car is plain and simply better at putting it's power to better use than any other in the corners and this has been proving in every test that has been conducted. Why can't you all agree this simple fact.

As others have pointed out foot, and what you just can't seem to get, is that in an apples to apples comparison the GT-R, with STATED specifications SIMPLY CAN NOT best all of the other cars we are talking about on the N'Ring, by the margins Nissan claims. PERIOD, PERIOD, PERIOD. Like another poster said, Nissan is dealing the marketing Kool-Aid and many are drinking up!

[footie]

Originally Posted by swamp2

There also seems to be a small minority who can not grasp a trend and prediction vs. an absolute statement. Power to weigh is THE MOST important factor in most performance categories. Obviously it is not the only one. No one EVER said that. It also varies much more than most other factors. I did the math for tires and for Cd x A, etc. Power to weight varies the most.

Let me welcome you to this thread swamp, it's been going for some time and little or no input from yourselves.

Swamp, as always we seem to be at odds on one thing or another but on this one I am in total agreement if in a round about way. Yes power and weight are the most important factor but like you highlighted, not the only one. PTW's biggest importance is in acceleration and mostly from a standstill, after about 80mph or so this figure becomes less important and the actual power becomes top dog. Secondly, weight has a big bearing on handling and braking but have a bigger effect on slow speed corners which unfortunately the ring has little of.

May I ask, if you believe PTW is the most important factor then why is a Lotus Exige with PTW of 238hp/ton no faster than an S5 with only 216hp/ton or better still, a 335i with just over 205hp/ton. To me the reason is outright power and the ring is a power track, plus the Exige is a track star for proper race tracks which the ring is not, it's a road course with loads of bumpers which is most likely upsetting the Lotus. Another factor will be aerodynamics which increases it's effect the higher the speed.

Originally Posted by swamp2

You answered your own question: The Veyron was not designed at all as a track performer. It was designed to be a 1000+ hp acceleration monster that your grandmother can drive. GT-R was designed in a more impressive fashion; fast in the straights and turns and also something your grandmother can drive.

Of course I answered the question, why make people guess the answer and prolong the debate.

Originally Posted by swamp2

Let me repeat...

There also seems to be a small minority who can not grasp a trend and prediction vs. an absolute statement. Power to weigh is THE MOST important factor in most performance categories. Obviously it is not the only one. No one EVER said that.

Also the power to weight advantage of the M3 CSL is HUGE, very close to 20% That was a really poor choice to make a case.

Re-read my first paragraph, this explains why PTW isn't as much of an importance on the ring as with other tracks and other disciplines. My point of the M3CSL argument was to prove that there are exceptions to the rule and like the CSL, the GTR is one of those cars which defy logical thinking.

Originally Posted by swamp2

As others have pointed out foot, and what you just can't seem to get, is that in an apples to apples comparison the GT-R, with STATED specifications SIMPLY CAN NOT best all of the other cars we are talking about on the N'Ring, by the margins Nissan claims. PERIOD, PERIOD, PERIOD. Like another poster said, Nissan is dealing the marketing Kool-Aid and many are drinking up!

Can't agree here, there is too many factors other than PTW that will determine any car's time on the ring. Maybe on the same day as the GTR's time was achieved the Viper and ZR1 might have went even faster, who knows. I believe Nissan's claim but disbelieve their quoted output figures, though I don't believe people's suggestions of over 600hp, about 525hp sounds about right to me.

[swamp2]

Originally Posted by footie

Let me welcome you to this thread swamp, it's been going for some time and little or no input from yourselves.

Swamp, as always we seem to be at odds on one thing or another but on this one I am in total agreement if in a round about way. Yes power and weight are the most important factor but like you highlighted, not the only one. PTW's biggest importance is in acceleration and mostly from a standstill, after about 80mph or so this figure becomes less important and the actual power becomes top dog.

Mass is always important F=ma, always (unless you are small or fast enough to be quantum mechanical or relativistic....). Perhaps what you are trying to say is the as speeds increase the effects of drag become the dominant resistive force.

Originally Posted by footie

May I ask, if you believe PTW is the most important factor then why is a Lotus Exige with PTW of 238hp/ton no faster than an S5 with only 216hp/ton or better still, a 335i with just over 205hp/ton. To me the reason is outright power and the ring is a power track, plus the Exige is a track star for proper race tracks which the ring is not, it's a road course with loads of bumpers which is most likely upsetting the Lotus. Another factor will be aerodynamics which increases it's effect the higher the speed.

Pretty much agree here. P/W is the most important factor. If you recall from the regression analysis (which we discussed for pages and pages). The R^2 value is very close to 1 but there still is significant standard deviation from the curve fit. The regression analysis is NOT a perfect prediction. No one ever said it was. The "other" factors such as tires, driver, track conditions, temperature, suspension and aerodynamics are the principal "other factors". Many of which I showed are not as significant as power to weight. The key point to remember is that the regression analysis gives you an idea of what an outlier really is and you can ascribe some mathematical likelihood of any outlier value being due to things like specs not equal to claims. It does not prove it 100%, just points strongly in a direction.

Originally Posted by footie

Re-read my first paragraph, this explains why PTW isn't as much of an importance on the ring as with other tracks and other disciplines. My point of the M3CSL argument was to prove that there are exceptions to the rule and like the CSL, the GTR is one of those cars which defy logical thinking.

The regression analysis was only peformed for the Nurburgring only. Of course you would find that the SLOPE of the curve from the regression analysis will vary track by track and my strong belief is that the slope of the curve will be larger in magnitude for a high speed track as compared to a low speed, autocross type of track. The R^2 value (or quality of a the linear curve fit) will also vary track by track. Tracks that are high speed and high power tracks would likely show a larger R^2 value.

Originally Posted by footie

Can't agree here, there is too many factors other than PTW that will determine any car's time on the ring. Maybe on the same day as the GTR's time was achieved the Viper and ZR1 might have went even faster, who knows. I believe Nissan's claim but disbelieve their quoted output figures, though I don't believe people's suggestions of over 600hp, about 525hp sounds about right to me.

As long as we agree that the 7:29 time was very likely not achieved with claimed hp specs we agree as much as we need to. :-)

[bruce.augenstein@comcast.]

Originally Posted by swamp2

...As long as we agree that the 7:29 time was very likely not achieved with claimed hp specs we agree as much as we need to. :-)

So, based on the 7:29, what sort of power do you think the GT-R has?

Bruce

[swamp2]

Originally Posted by bruce.augenstein@comcast.

So, based on the 7:29, what sort of power do you think the GT-R has?

Bruce

A very good question. Often the shortest simplest quetion will get the longest answer . I will discuss, pose further questions and almost answer your question. There are multiple pieces of evidence that point to the actual power "the" car is producing. There is ample evidence that there is no "the" car in fact, this is one central problem. We have the widely varying 1/4 mi trap speeds to consider as well as the N'Ring times and other lap times. One key problem with the N'ring time comparisons and lucids previous regression analysis is that these GT-R times are all "factory best" as opposed to a Sportauto time. IIRC most of the data in lucid's regression analysis were all (or almost all) Sportauto times. As you know the preliminary Sportauto time for the GT-R (with the caveat of a "partially wet track") is a mere 7:50.

Your guess about what the trap speeds mean is every bit as good as mine but those numbers indicate a very wide range of power outputs from roughly the claimed value to much much greater than claimed, perhaps as much as 550 hp. Inconsistency and huge variations are the key issues here which you yourself have very appropriately emphasized in the past. Some results are consistent with the cars stated power output, others are clearly not. The next things to consider are the following key questions.

1. How much power do I suspect the car that did the 7:29 is putting out or what do the regression models say about the likely power output? Different questons of course. Perhaps my big new insight here is that it is NOT appropriate to compare "factory ace" times to lucids regression model. The point seems obvious, but it also seems all of us missed this one thus far. You could roll the effect of driver into the model better and allow all drivers in the model as well and simply consider them another part of the variation.

2. What time will Host/SA obtain under more fair and ideal conditions? The regression model using the 95% confidence best case fit (most amount of an over performer) predicts a 7:50 time, purely conincidental with the thus far achieved time of 7:50. My strong suspicion is that he will obtain a time of 7:4X. Why is the car faster than even the 95% best case predictions from the appropriate regression model? Again a combination of great tires, great chassis, great AWD system, great traction control, etc. all doing a very good job especially in the corners where P/W is less important.

3. What we really need to have is a separate regression analysis for "factory ace" times. We are still running up against (myself included) the inappropriate comparison of Nissan's factory ace times vs. Sportauto times. Clearly a factory ace with ample factory support and tweaking will be able to cut 5+ seconds off of the SA time. A few data points that justify this are: Walter vs. Horst in the Carrera GT, 7:28 vs. 7:32, only a 4 second gap; Motortrend being only 2 seconds behind Porsche figures for the 997 Turbo and finally the Z06 with a 6 second difference between SA and factory driver. These differences mean than Horst should be capable of obtaining a time in the 7:3X range instead of the 7:4X range if piloting a car equivalent to the one that did the 7:29.

"Conclusions": If the official Sportauto time is 7:4X I will be content that that particular car meets quoted specifications and that Nissan has done a pretty brilliant job with the systems in the car I mentioned above. However, if they get a 7:3X time, I will strongly suspect the car does not meet published specifications, most likely in the power category. Breaking the 7:30 time with 480 hp and a 3800 lb curb weight is still, despite how well the car behaves and performs on the track and despite being piloted by a factory ace is IMO not possible. This is a lb/hp ratio of 7.9. Consider again these cars (which have also been highly designed and engineered for incredible lap times as well). I know I am probably beating a dead horse but consider the numbers. We are not talking minor differences here, we are talking about almost a 2:1 factor in some cases, 2:1 and minimally 1.4:1.

Car, time, lb/hp
Enzo, 7:25, 4.6
ZR1, 7:26, 5.5
Carrera GT, 7:28, 5.0
Zonda F Clubsport, 7:32, 4.2
Koenigsegg CCX, 7:33, 3.50

Even if the GT-R out corners some of these cars, when in the straights or near straights and under good traction and WOT or near WOT, these cars will be accelerating SO MUCH harder than the GT-R.

[footie]

Great to see that on this occasion we are not to far apart.

But may I throw another car into the pot which steps even further out of the regression analysis than any other. The Renault Megane R26R, this car has 227hp and weights in at 1230kgs, that's a whole 300kgs more than the Lotus in my previous post and yet it's a full 9 seconds quicker.

Now at what point will this insistence that the RA being a good rule of thumb be acknowledged that on some occasions it's not always right, or even near right.

I also understand why some here, like yourself look at Horst's and Sport Auto's times and say they are pretty close to factory claims, the Porsche being one example of this but there are times that we will see huge differences.

I'm quite sure that the GTR is producing 10" more power than quoted, the same is true for the Veyron, why Nissan are possibly doing this to guarantee that it's better than the 997TT because it's weight slipped beyond it's target weight they had set for it.

P.S.
I have a theory on why the GTR might be able to compete with your list of supercars when they all approach on to the straight. The nurburgring is a hell of a bumpy track, putting all 600+hp through just 2 wheels to a surface such as this would be extremely difficult, chances are the throttle needs to be feathered until well on to the straight. Such problems are probably not there for the GTR driver to experience so his 525hp (if that's what it is) can be put down even before the corner is fully exited.