centurion
Well-Known Member
Re: Nissan is a liar! - Porsche
The GTR has full active diff front and rear.
The Porsche Turbo ... lol .... has ... umm... haldex viscious coupling as standard.
There is an active differential though, named PTM (porsche traction management) which is GREAT but it is an OPTION.
One wonders whether Nissan and Porsche are talking about different cars. Nissan using the non-PTM one and Porsche using the PTM one.
And both know it but dun wanna say ????
one point many people ignore and I forgot also.axl;386620 said:Wow... good rebuttal.
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Your model, while useful is simplistic in that it only considers part of the picture. Power to weight is certainly a good and useful indicator of performance, but you must add in other factors which are very significant:
Rolling resistance, including bearing and tire friction: Nissan has repeatedly stressed that power to the ground is much higher for a GT-R than conventional cars due to the very low friction of the drive-train compared to conventional sports cars. This makes the use of BHP for the GT-R less relevant. Rolling resistance of tires is an unknown for the GT-R, and not likely significant at high speed.
Aero drag and frontal area: GT-R has a much lower drag than typical sports cars at 0.27 and it makes downforce. This means a much higher speed down the straights than a typical car ( in particular those with downforce). Grip is also higher since most cars have lift at high speed and those with any downforce (extremely rare in road cars) will have much higher aero drag. The GT-R has a phenomenal lift to drag ratio for a road car, and this is a very significant factor in it's high speed potential both in terms of top speed and cornering grip. A conventional sports car with the same BHP would not go nearly as fast down the straight, and when you couple this with the higher power to the ground for the stated BHP, you have a significant factor ignored in the BHP/weight ratio.
Shift speed: GT-R shifts much faster than a conventional sports car, and this must be factored in. How many shifts per lap times benefit per shift needs to be added in to the mix.
Center of gravity height: GT-R has gone to significant lengths compared to other cars to lower center of gravity. A lower cg reduces weight transfer and thus provides more grip from each pair of tires on an axle than does a car with a higher cg.
Corner exit speed: this is based on being able to put down the power without spinning the tires. If you can go to full throttle faster than other cars because traction control and car balance allow it, then car will be faster on every corner exit than conventional cars.
Balance in transitions: data logger printouts from Steve Millen's drive on track for R&T mag showed that GT-R was much faster (by a very wide margin) than other cars tested though a series of esses at Buttonwillow. It was also much, much faster through several other sections. If during a series of transitions on track you cannot confidently put the power down, you will need to back off to make certain the car is settled as it changes direction. It would seem the GT-R can do this much better than other cars on a race track. If one looks at the following speed vs distance charts for the Z06, GT-R and 997 turbo, one can see that the cars are very close in many sections, but the GT-R (red curve) is much, much faster in several areas and over a long distances than the other two cars. This can not be explained in any way by a simple BHP/weight ratio comparison.
http://www.roadandtrack.com/assets/download/0508_ct_OnTrack.pdf
The GT-R is so much faster than the other two cars through the esses and it appears to defy physics. Power to weight ratio would only apply to compare part of the lap.
One can see from the deceleration sections that the GT-R does not gain much if any under braking. It's gains are virtually all made while on the gas. It would be interesting to see a comparison of the throttle pedal tracks. I would think the GT-R is at full throttle much more than the other cars on that lap, allowing it to gain significant advantage.
I have done hundreds of lap simulations using Lapsim (and thousands of laps on track), and while power to weight is a primary determinant of lap time, it is only a small part of the picture. Not to take away from your chart and the standard deviation trend-lines, which I found most interesting. Assuming of course the GT-R did those lap times at the Ring which I believe, one needs to look at the car's other dimensions to see why it is a new "yardstick" and why Porsche and others would buy one to dissect and analyze it.
The GT-R is a 3 Sigma event!
The GTR has full active diff front and rear.
The Porsche Turbo ... lol .... has ... umm... haldex viscious coupling as standard.
There is an active differential though, named PTM (porsche traction management) which is GREAT but it is an OPTION.
One wonders whether Nissan and Porsche are talking about different cars. Nissan using the non-PTM one and Porsche using the PTM one.
And both know it but dun wanna say ????
