I'm getting kind of lost by this thread, so I thought I summarise it to save new readers having to spend hours on the old posts. The thread is as follows:

1. Nissan say the GTR is quick at the ring and provide video proof.

2. All the magazines globally driving both customer and manufacturer cars, also say ' wow this is a great car' and is faster than a 997TT and about the pace or better of a GT2.

3. A Porsche engineer says unofficially in Australia that they found the GTR not as quick as expected.

4. Some gearboxes blowup when owners who believe The Fast and Furious is real do far too many launches.

5. Many people are not surprised that launching a 1700kg+ 4wd car with sticky tyres might be problematic.

6. Some others decide this is a scandal and warrants a class-action suit (don't we love US law).

7. Some Porsche fanboys decide that this makes everything Nissan ever makes poor quality.

8. Other Porsche fans don't care anyway as they only buy cars based on what courtesy cars they are provided by the dealer.

9. Some Porsche owners who have driven the GTR, including some who drive at the ring state very clearly they think the GTR is a very fast and capable car. Other Porsche owners who have never driven a GTR or been at the ring decide that the GTR isn't. Clearly these people have not heard of irony!

10. The thread then loses all sense of purpose as clearly like all these threads we have a bunch of intransigent fanboys from both camps, who have no respect for the other side. Might as well be a Corvette vs Camaro forum from the quality and substance of many posts from both Porsche and GTR supporters.

11. Most importantly, we have many people who clearly believe that there has been a global conspiracy to make the GTR seem faster than it is actually is, even though Nissan stopped producing the GTR completely for 6 years to concentrate solely on building a car that established new standards with new technology.

I'm really bored of this now.

Guy

 

Swamp2,

I read your piece on the ring video with interest. I would like to get your thoughts on two points in terms of the data/analysis.

Firstly, your analysis is pretty much solely based on power/weight and tries to establish that the GTR is under-rated i.e. it makes more than 480bhp. Your conclusion is that it does, but if this is a feature of every car, then I'm not sure what the point is, except that Nissan are choosing to be conservative with stated power (like Ruf do).

Secondly, your analysis on sigma of 'ring performance is all about outliers on performance based on power/weight ratios. You note one such outlier is the M3 CSL. I also happen to own one of these and have spent many days at the ring in it, including the Scuderia Hanseat 4 day training course which I've done a few times. The thing to note is that the CSL makes it's time up by having such a composed chassis and great cornering speed, which matter often far more than power/weight since the ring is such a twisty course and there are few sections where sheer acceleration matter, such as the long straight at dottinger hohe and the uphill drag towards kesselschen (which by the way when you drive backwards or stop to walk it you realise is much steeper than you think when driving up it).

Anyway, my point is that Nissan spent 6 years designing this car, with the sole aim of producing something that moved the game on and was beyond that currently produced. Do you not think that in this case, with the technology that has been deployed that a high sigma variation is to be expected? If the CSL does a 7:50 'ring lap (which is not disputed), could not a car with far better traction (my experience of driving the GTR on the Silverstone GP track shows it has far superior exit grip at lower speeds than my CSL) and also a superior power/weight ratio therefore acceleration, as well as faster gearbox, be faster?

Based on my experience of driving a GTR and also a CSL at the same track and based on my limited 'ring experience (a few hundred laps over perhaps 20-30 days spent there), I find it quite believable that a GTR would be 10+ seconds faster, putting it into the low 7:30s.

Guy

 

Although I think it is highly improbably and shocking, I', with you-- I think it could be true.

I wonder if the statistical modeling takes into account the benefits of dual clutch (Porsche claims 8 secs faster Ring laps with PDK) and state-of-the-art Turbo controller, AWD and VDC systems.

 

How does 10+ seconds faster than 7:50 = low 7:30's???

 

It's the "+" bit, it means "more than".

Again, have you driven a GT-R?

What do you drive?

 

Yeah damage control, that is really funny for someone who consistently does not read and changes the topic.

Perhaps I have not made my position clear, and since you are assuming things about my personal opinions of the GT-R, let me simply set the record striaght. I really like the GT-R. Being a technical person myself I can really appreciate many things Nissan did with the car. Their DC transmission is great (except noted longevity/warranty problems), their AWD system seems to be about the most advanced ever released in a production car. Just in general the car is a huge achievement in software and software that really matters. I fully acknowledge the immense praise the car has obtained in the press and think most of it is well deserved. I do believe a bit of the Nissan hype as well that this is a supercar than anyone can drive. This is a huge achievement. On looks the car does not do much for me, but beauty is, of course, in the eye of the beholder. OK, back to the original point, since I have proven you blantantly wrong with your classification of me.

What I am saying, if you bothered to read the post in my link carefully, is simply that all evidence points to the particular GT-R that obtained the 7:29 lap time being substantially under rated. That is it, period.

 

Good, post, mostly agree except for the rather enormous math error HC pointed out.

The regression analysis is indeed for a single variable, the weight/power. I have performed other regressions looking at things like CdxA and lateral grip and others. Power to weight rules, period. The E46 M3 CSL is indeed an over performer as indicated by the regression analysis, but only by under 2 standard deviations. The GT-R at 480 hp is 3.5 standard deviations out. This is a HUGE difference when you understand statistics. What will make an over performer is obviously a design with intent purpose above and beyond a normal sports car to obtain great lap times. Tires, suspension, aerodynamics, chassis, DC gearbox, and brakes can all contribute to making a car an over performer or even outlier when enough of these effects are stongly combined. The numbers show this for cars like the ACR, Donkervrort, Mosler, CSL, etc. that mostly accomplish it with tires, suspension and aero.

It really doesn't matter how much of these additional factors you throw at a car, if its power to weight is not high it just can't perform with the others that have much better values. Such a low power to weight vehicle can certainly make up ground with the factors above, but it is very difficult to overshadow P/W with them. We all know that power to weight rules in drag racing (assuming traction is adequate). How much of any given track is spent at WOT under heavy acceleration?

Hope this helps, thanks for having a look at my work.

Any time in the high 7:30s to 7:40s would be at least possible and mostly believeable and that seems to be what you meant to say. I think we are in agreement.

 

Out of curiosity, aren't the transmission and AWD systems engineered by German companies? The AWD is Bilstien, Tranny Borg/Warner?

 

Sorry to be broken record, but Dual Clutch is a large enough variable that it cannot be ignored-- especially for a Turbo car. The Ring has lots and lots of corners and some very long straights. On Straights, GT-R can accelerate with 600HP+ cars. Search my posts in the thread for a chart showing GPS data where I prove this.

DC also helps in technical parts of the track where optimal gear selection needs to be balanced with time required to shift. Given the near-zero shifting penalty in GT-R (or PDK 911), you will be in the ideal gear more of the time with DC.

Take these small advantages and spread them across all the turns and straights in a very long track, and you start to understand that some of your "sigmas" are actually systematic bias in your model due to failure to account for the shift-time variable.

Power/weight is a reasonable simplified model for in-gear acceleration for cars with more or less the same drivetrain, but not when the "baseline" car model is a stick, and the "subject car" has DC and you're talking about lap times.

 

I think the base tranny tech came from Borg-Warner, but the final gizmo was from a J/V with a Japanese company. All cars these days are assembled from subsystems from other vendors.

Not sure about AWD, but would not be surprised.

I assume that these systems were not off-the-shelf, but were highly tweaked to Nissan spec.

-Chris

 

Almost double? Never meant that much when I've seen it.

Looks like bad math to me.


Sont worry about what I drive, I dont owe you any explanations. My history is here, if anyone, it's YOU that needs to prove something around here.

TROLL

 

HC, now that you've read Swamps analysis, do you still think that the GTR that ran 7:29 is not under-rated?

 

That's the point!!!!!!!!!


If the GT-R that ran the ring was 600 hp you'd be calling it underrated. I call it cheating because there arent any other 600 hp GT-R's.


Get the idea now??



Anyways, more trannies failing!!! More warranties voided.

http://www.nagtroc.org/forums/index.php?showtopic=25807

 

What! I've always stated in the begining that they're cheating on their hp rating, hence under-rating. I still don't believe that the GTR that you'll buy from the dealer is only making 485hp, maybe not as much as the one that they tested in The Ring, but still under-rated. Just base on all of the dyno test that i have shown you, anywhere from 430hp to 460hp on the wheels, that means anywhere from 510 up to 540 or more if you calculate minimum 15% loss. No way they're only losing 10% on the wheels.

 

This is one of my post stating that they cheated, from post #225. The difference is, you HC have always said that Nissan cheated using different tires and you don't believe the video. I've always said that the video is real, they did 7:29 in the Ring but that particular GTR they used is under-rated and you insisted that no way the GTR can have 540hp.