Originally Posted by bruce.augenstein@comcast.
Forgive the interruption, but I'm having a problem with this list, and the general thrust of it.
I don't take contention with most of what you say. Again there is evidence on both sides of this potential under-rating topic. I would admit my list of evidence was the evidence FOR a possible under-rating, not necessarily the best nor most complete possible list to show an honest rating. I think your biggest find/eye-opener is on the torque split. Much more on that later...
My comments and contentions are:
Our regression analysis as well as a bit of common sense showed that N'ring times are indeed dominated by power to weight. It is a fast track that obviously favors high hp just the same way the 1/4 mi run does. Tires, driver and other effects are obviously significant factors, and I think those two are the largerst after power to weight. Suspension can be a big factor but I suspect there is just ulimately too little variation in practice to see much of an effect here. I did add lateral g force (as an overall measure of tires+chassis+suspension) as a regression parameter and although it did have an effect it was quite small. So again lap times are absolutely dominated by power to weight. By the way do you recall the sensitivity study done with varying number of cars by lucid and another by me? Not only did that show very little effect, the large number of cars themselves represent a nicely semi-randomized group of events. Not perfect data, surely, but as good as we have and good enough to draw a solid conclusion from.
What exact problem do you have with the ace driver point? This is a mitigating factor AGAINST an under-rating theory. With a top notch driver that Nissan had he could get a better time than most, certainly better than Horst, and this would be an effect that looks like an under-rating but then actually is not. It is simply an ace driver.
On the tires, who knows, may be as good as a PS2, maybe a PSC+ maybe not a PSC, who knows. Given the history and what run flats have achieved to date I'll trust you that it is unlikely that these tires will perform as well as a PSC. Given the level of innovation we see in the car...
I'm not sure exactly where I stand on the drive train losses of the GT-R vs tiptronic. The GT-Rs drivetrain loss is almost for sure > 997TT 6MT but do the extra cases and shafts balance out vs. the AT? Might be close.
I think you are on to something here with the variable F/R torque split. A modern and sophisticated AWD is able to effectively limit power losses (and preserve good steering feel as well) to figures much closer to a TWD equivalent system when the transmission to the front wheels can be almost disenegaged. If the vast majority of the power is routed this way on acceleration this can make the car accelerate closer to a TWD equivalent. A quick check indicates Audis quattro system has a permanent 40/60 split F/R whereas the Carrera system can vary the split between 40/60 to 5/95. The GT-R varies from 50/50 to 2/98 and it makes adjustments every 20 ms! (Side note BMWs xDrive system can vary between 0/100 and 100/0 but I can not find how often it adjusts). Hence the characteristically high drive train loss we see on the RS4 and hence also the close acceleration times you have found comparing C4 vs C4S. Time for some more simulation! I need the ability to switch off the AWD after launch which I am having a hard time figuring out how to do immediately... Another important factor as far as handling and preventing torque steer during hard acceleration will be the further ability to split the power left to right as well as fore to aft and I suspect the GT-R does this nicely at both ends.
I have never said that there is nothing special about the GT-R, period. What I have said is that it is unlikely that Nissan has entirely reinvented the sports car. I'll be the first to admit and congratulate Nissan for the technological prowess of the car (and have made these statements over and over and over again all over this thread and other places in the forum). The drivetrain is likely one of the most advanced around but the suspension being active/adjustable and user configurable is nothing particularly new and not something that has shown to be an enormous effect on laptimes nor on absolute grip level, etc. Do keep in mind the "lowly" Evo can adjust it's F/R torque split amost identically to the GT-R (a bit more control actually, 50/50 to 0/100) and does so actively as well. The question is can it adjust it as often or as quickly as the GT-R.
I have heard the rumor that Nissan is shooting for SAE certification of "around" 480 hp. I posted the exact quote earlier in this thread. However SAE hp certification is 100% voluntary, correct?
Thanks for some good points and definitely points that matter toward getting to the bottom of this issue.