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      12-22-2007, 11:32 PM   #196
Lieutenant Colonel

Drives: Legacy GT - 13.704@99.39
Join Date: Jul 2007
Location: Manheim, PA

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Originally Posted by swamp2 View Post
Perhaps you do not understand evidence vs. proof? Let's revisit the evidence. This all been beat to death but you seem to have missed it, typical. Each piece of evidence does have mitigating factors as well which I will point out. Again these mitigating factors are what makes this really a matter of science and something that requires an investigative approach and requires mutiple, consistent pieces of evidence to make any final calls.
Forgive the interruption, but I'm having a problem with this list, and the general thrust of it.

Originally Posted by swamp2 View Post
[*]The N'ring laptimes on a track absolutely dominated by power to weight ratio. Mitigating factors include an ace driver, DCT, likely VERY sticky UHP tires similar to a MPSC or MPSC+.
Who says the lap times are absolutely dominated by power to weight? There appears to be some correlation, but until you have say, five hundred passes using the data you've been using, or a fewer number (but still large) using data from strictly controlled passes (weather and driver, mostly), you have at best a loose correlation. There are bunches of flyers (some greater than others), and most don't fall on a statistical line.

This is like saying that quarter mile passes vary by the cube root of the power to weight ratio. That's also statistically true, but traction, gearing and weather absolutely screw up the results on a car by car basis.

It's also pretty much like saying that the GT-R is Massively under-rated...

I also have trouble with two of the the mitigating factors. Ace driver? Nobody's better than Rohrl, and his 7:40 Porsche Turbo time is proof enough. As for the tires, I'm willing to believe that Nissan and Bridgestone have established a higher performance plane for runflats, but up until now, nobody's done a runflat that will stay with, say, a PS2, Advan Neova or Falken Azenis. Let's say the new combo will run with those stalwarts and leave it at that. A PSC competitor? Not likely as yet.

Originally Posted by swamp2 View Post
[*]The dyno test of the GT-R. Mitigating factors include accounting for tire loss, the likely dynapack non-conservatism, other observed inconsistencies in the dyno results.
Artpe's commentary on this test ought to throw enough doubt into the proceedings that one would likely throw that data out - although I must say his analysis showing the dyno rigged for a 17.5% shortfall is food for thought. If so, that would mean the car may be rated accurately.

Originally Posted by swamp2 View Post
[*]Comparisons with the 997TT performance figures. This car has more torque and weighs quite a bit less than the GT-R and very likely has less drivetrain losses. There is dyno evidence and simulation evidence as well for the 997TT being under-rated. Mitigating factors again include the DCT.
I would argue that the GT-R has arguably less drivetrain loss compared with the "fast" (meaning Tiptronic) Porsche. The extra driveshaft will add little in the way of friction and rotational loss compared with the Tiptronic losses.

Originally Posted by swamp2 View Post
[*]Simulation results indicate an under-rating. Both mine and Bruce's in fact since his system gets reasonable predictions for the cars time but misses all the hp lost in the car's complex drivetrain.
My simulations of these cars indicates an under-rating down in the noise level for both cars. When you're down in the one or two percent range in a simulation, that's pretty much dead on balls accurate (as per Marissa Tomei in "My Cousin Vinny").

I'd also question the power lost to a sophisticated awd system, The normally aspirated 911S vs the 4S shows very little difference in both quarter mile times and speeds, and since the Turbo uses the same system, it's likely to be very efficient as well. Note that very little power is transferred forward in these cars, and essentially none if traction isn't an issue - which it won't be for most of a quarter mile. If power isn't being transmitted, there's no loss, and these are lightweight parts indeed since they never transmit a lot of torque. I can't speak for the GT-R, but assume it will be at least as sophisticated.

Originally Posted by swamp2 View Post
*]History: Nissan is well known for under-rating Skylines/GT-Rs in the past.
This is simply not admissable as any sort of evidence in my opinion. The government-inspired manifacturers' pact in Japan to limit power to a published max has been gone for a long time, and the last Skyline tested by C & D seemed to be pretty close to published ratings.

Originally Posted by swamp2 View Post
There is probably more evidence as well but these were just quickly from memory.
There are two pieces of evidence you've left out. One is Edmunds' experience that their Porsche was quicker than the GT-R on the street in mid-range and up acceleration, although markedly slower in the twisties.

The other is in the form of a question. In this current day of no restrictions on Japanese cars and 500 and 600 horsepower cars coming out of Europe and the States, why on Earth would Nissan bother to lie, especially since they're going to face the SAE music shortly?

Swamp, your list smacks of a biased train of thought. When I combine this with your commentary that's there's nothing special about this car, it makes me wonder about your motives. As fas as I can tell, pretty much everything is special about this car.