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    May 28, 2008 5:14:09 AM

    ADias
    Rennteam Pro
    ADias
    Loc: Southwest USA , United States
    Posts: 2495, Gallery
    Registered on: Apr 9, 2004
    Reply to: xandi911

    Re: GT-R: The story behind the 7.29 lap

    Quote:
    xandi911 said:
    Quote:
    Jeff (in SF) said:
    Quote:
    nberry said:

    Carlos, I did not claim everything Newton espoused was wrong. All I said was Einstein proved Newton wrong. I did not state on which theories until Fritz called me on it. I then proceeded to show where Einstein proved Newton wrong.





    By analogy, better measuring accuracy and computers have enlightened us to know that "P"i is more accurately described as 3.1516.........(insert thousands of digits here after the decimal point),



    3,1416



    Nice catch.

    May 28, 2008 3:15:21 PM

    nberry Offline
    Rennteam VIP
    nberry
    Loc: La Jolla, USA , United States
    Posts: 13737, Gallery
    Registered on: Apr 11, 2002
    Reply to: Jeff (in SF)

    Re: GT-R: The story behind the 7.29 lap

    Quote:
    Jeff (in SF) said:
    Quote:
    nberry said:

    Dynamics of a rear engine car are totally different than a front engine. An engine sitting behind the rear axle is at a distinct disadvantage.




    So, Nick, are you ever going to explain what you meant by what you meant here? Specifically I'm asking what is(are) the disadvantage(s) of a rear engined car. You took this thread on a bizarre turn debating the merits of physicists from disparate centuries but my original question was simply for you to elaborate on what you meant by your blanket statement that a rear engined car is at a disadvantage when it comes to driving dynamics. What do you mean?



    Rather than me explaining it to you, it would be in your interest to educate yourself so that you become better informed.

    May 28, 2008 8:24:49 PM

    Jeff (in SF)
    Pilot
    Jeff (in SF)
    Loc: SF, CA, USA , United States
    Posts: 340, Gallery
    Registered on: Nov 13, 2003
    Reply to: nberry

    Re: GT-R: The story behind the 7.29 lap

    Quote:
    nberry said:
    Quote:
    Jeff (in SF) said:
    Quote:
    nberry said:

    Dynamics of a rear engine car are totally different than a front engine. An engine sitting behind the rear axle is at a distinct disadvantage.




    So, Nick, are you ever going to explain what you meant by what you meant here? Specifically I'm asking what is(are) the disadvantage(s) of a rear engined car. You took this thread on a bizarre turn debating the merits of physicists from disparate centuries but my original question was simply for you to elaborate on what you meant by your blanket statement that a rear engined car is at a disadvantage when it comes to driving dynamics. What do you mean?



    Rather than me explaining it to you, it would be in your interest to educate yourself so that you become better informed.



    How predictable. You don't disappoint in your predictability. Aside from the welcomed correction on the abbreviated Pi figure, I've demonstrated my competence in this area and thus am confident proclaiming myself "informed". I look forward to future exchanges with you where I, and the many others of this board, will further assert my/our automotive competence to your private dismay. Jeff in SF 1, Nick 0

    May 28, 2008 8:29:14 PM

    Jean
    Veteran
    Jean
    Loc: Seoul , South Korea
    Posts: 1033, Gallery
    Registered on: Apr 14, 2002
    Reply to: deathnell

    Re: GT-R: The story behind the 7.29 lap

    Quote:
    deathnell said:
    The 7:29 video is going to release by Best Mortoring from Japan



    YEAH!

    May 28, 2008 8:55:35 PM

    Jeff (in SF)
    Pilot
    Jeff (in SF)
    Loc: SF, CA, USA , United States
    Posts: 340, Gallery
    Registered on: Nov 13, 2003
    Reply to: Jean

    Re: GT-R: The best explanation I've heard so far..

    While I'm not an avid reader/fan of Motor Trend, they supposedly got their hands on the first US customer spec car (not a press fleet car). Here are the key areas they say that helps the GTR achieve the hard to believe numbers.

    1. First the obvious - it puts out more power than Nissan claims. They put it on a four wheel Dynojet inertia-type dynamometer and using very conservative assumptions about friction losses, etc., Motor Trend calculates that the GTR must be putting out at least 507hp at 6800 rpm and 500 lb-ft torque at 3200 rpm.

    2. Dual clutch transmission provides uninterrupted acceleration when changing gears while other cars "coast" in neutral until the next gear is engaged. Nissan claims .2 sec from the time you flick a paddle until the next gear is completely engaged however the car is still able to accelerate in its current gear during those .2 seconds. In the 1/4 mile sprint, a 911 turbo needs 3 shifts (according to MT) and with its regular manual transmission requiring approx .2 to .25 seconds per shift, the GTR is able to put its power to the pavement and generate acceleration for almost .75 seconds longer than the 911 Turbo can in the 1/4 mile sprint. Said another way, the 911 Turbo is "coasting" in neutral for .75 seconds while the GTR continues to accelerate. Ferrari and BMW claim quicker shifts (.1 and .15 seconds respectively), but those cars also can't escape the "coasting" effect during the gear change when it's effectively in neutral which costs some time. Bottom line, the dual clutch transmission is a big part of the Nissan's advantage especially when you consider how much shifting is done over an 8 minute lap.

    3. The 15" brakes on the GTR are dialed in perfectly for the car. In their tests, it's the 5th best (shortest stopping car from 100mph) behind the Ferrari F430 and Porsche Carrera GT.

    I've never driven the 'Ring so I won't comment these 3 areas highlighted by Motor Trend make the most sense to me. I'd also guess tires played a big part but they didn't investigate those in the article. It would also seem reasonable that Porsche's forthcoming DSG transmission will negate the GTR transmission advantage pretty quickly and if the 911 Turbo can post competitive lap times now, I wonder how much we'll see those lap times fall when equipped with a transmission that's always putting power to the pavement under throttle.

    May 29, 2008 5:57:45 AM

    AUM
    Veteran
    AUM
    Loc: Germany
    Posts: 1203, Gallery
    Registered on: May 2, 2006
    Reply to: Jeff (in SF)

    Re: GT-R: The best explanation I've heard so far..

    The GTR also carries more speed through corners than a GT3 due in part to its AWD system and suspension set-up (not to traction control which is turned off for fast laps). The run-flat tires cannot be as sticky as cups but they do seem to work quite well,

    May 30, 2008 5:23:10 AM

    xandi911
    Senior
    xandi911
    Loc: brasil
    Posts: 688, Gallery
    Registered on: Feb 14, 2006
    Reply to: Jeff (in SF)

    Re: GT-R: The best explanation I've heard so far..

    Quote:
    Jeff (in SF) said:
    While I'm not an avid reader/fan of Motor Trend, they supposedly got their hands on the first US customer spec car (not a press fleet car). Here are the key areas they say that helps the GTR achieve the hard to believe numbers.

    1. First the obvious - it puts out more power than Nissan claims. They put it on a four wheel Dynojet inertia-type dynamometer and using very conservative assumptions about friction losses, etc., Motor Trend calculates that the GTR must be putting out at least 507hp at 6800 rpm and 500 lb-ft torque at 3200 rpm.

    2. Dual clutch transmission provides uninterrupted acceleration when changing gears while other cars "coast" in neutral until the next gear is engaged. Nissan claims .2 sec from the time you flick a paddle until the next gear is completely engaged however the car is still able to accelerate in its current gear during those .2 seconds. In the 1/4 mile sprint, a 911 turbo needs 3 shifts (according to MT) and with its regular manual transmission requiring approx .2 to .25 seconds per shift, the GTR is able to put its power to the pavement and generate acceleration for almost .75 seconds longer than the 911 Turbo can in the 1/4 mile sprint. Said another way, the 911 Turbo is "coasting" in neutral for .75 seconds while the GTR continues to accelerate. Ferrari and BMW claim quicker shifts (.1 and .15 seconds respectively), but those cars also can't escape the "coasting" effect during the gear change when it's effectively in neutral which costs some time. Bottom line, the dual clutch transmission is a big part of the Nissan's advantage especially when you consider how much shifting is done over an 8 minute lap.

    3. The 15" brakes on the GTR are dialed in perfectly for the car. In their tests, it's the 5th best (shortest stopping car from 100mph) behind the Ferrari F430 and Porsche Carrera GT.

    I've never driven the 'Ring so I won't comment these 3 areas highlighted by Motor Trend make the most sense to me. I'd also guess tires played a big part but they didn't investigate those in the article. It would also seem reasonable that Porsche's forthcoming DSG transmission will negate the GTR transmission advantage pretty quickly and if the 911 Turbo can post competitive lap times now, I wonder how much we'll see those lap times fall when equipped with a transmission that's always putting power to the pavement under throttle.



    the dual cluch transmission of GT-R is done by nissan or another factory?

    will be the PDK at mininum as good as the GT-R transmission?

    i think is time to porsche take some knowhow with nissan

    Jun 1, 2008 6:05:12 PM

    plz
    Junior
    plz
    Loc: tx, usa , United States
    Posts: 68, Gallery
    Registered on: Sep 28, 2005
    Reply to: Jeff (in SF)

    Re: GT-R: The best explanation I've heard so far..

    Quote:
    Jeff (in SF) said:...I wonder how much we'll see those lap times fall when equipped with a transmission that's always putting power to the pavement under throttle.



    I think the DCT only puts power to the pavement during upshifts when the next higher gear is pre-selected. On donwshifts that is not the case AFAIK. Downshifts are quite a bit slower than upshifts. Not sure what is the ratio of upshifts/downshifts on a lap of the NS but surely it has to be close to 1:1. So only half of the shifts will have the full benefit you describe. Still a large gain over pure manual I think.
     
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