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    Re: GT3 RS 4.0


    Re: GT3 RS 4.0




    Re: GT3 RS 4.0

    Great article many thanks!

    Looks like that 6RS is from Specialist Cars of Malton. 


    Re: GT3 RS 4.0

    Grant:
    BjoernB:

    I am amazed that a MANUAL car - where you clearly loose 0.3 seconds or more PER shift - can achieve such a time against a 458. It will be very interesting with PDK....

    Where did you get the 0.3 sec?  I think that is way over-stated.  Even if it takes someone 0.3 seconds to upshift, the car doesn't come to a dead stop during that time (it just isn't accelerating).  I think the difference is WAY smaller...

    On downshifting, there should be no difference with a good driver (since shifting and rev-matching is done during braking).

     disengaging the clutch - shifting and getting back the power on the tranny certainly costs 0.3 cents for sure - I have driven in Dijon RT and could clearly see this against PDK cars - it helps tremendously as you can concentrate fully on breaking-point and apex and the rest is done for you - very boring but certainly faster than even a experienced  manual driver. I am very sure that the same car with modern PDK would have easily gained another 1.5 or more seconds !


    Re: GT3 RS 4.0

    BjoernB:
    very boring but certainly faster than even a experienced  manual driver. I am very sure that the same car with modern PDK would have easily gained another 1.5 or more seconds !

    Boring? Not really. You can improve your "other" driving skills. Smiley There is always something to do for the driver, shifting just got a lesser priority than in the past.

    I fully agree...PDK gives a huge advantage. Wait until the first 991 GT3 PDK track times are available.

    I am actually waiting for the first sports cars which adapt to the track they are driving on (based on a super accurate GPS position). Before and after every single curve, the car knows how to down- and/or upshift, this would be amazing (or boring...depending on the view Smiley).


    --

    RC (Germany) - Rennteam Editor Porsche Panamera Turbo S, Cayenne GTS (958), BMW X3 35d (2012), Mini Cooper S Countryman All4


    Re: GT3 RS 4.0

    BjoernB:
    Grant:
    BjoernB:

    I am amazed that a MANUAL car - where you clearly loose 0.3 seconds or more PER shift - can achieve such a time against a 458. It will be very interesting with PDK....

    Where did you get the 0.3 sec?  I think that is way over-stated.  Even if it takes someone 0.3 seconds to upshift, the car doesn't come to a dead stop during that time (it just isn't accelerating).  I think the difference is WAY smaller...

    On downshifting, there should be no difference with a good driver (since shifting and rev-matching is done during braking).

     disengaging the clutch - shifting and getting back the power on the tranny certainly costs 0.3 cents for sure - I have driven in Dijon RT and could clearly see this against PDK cars - it helps tremendously as you can concentrate fully on breaking-point and apex and the rest is done for you - very boring but certainly faster than even a experienced  manual driver. I am very sure that the same car with modern PDK would have easily gained another 1.5 or more seconds !

    No Way.  I agree that the act of shifting takes about 0.3 seconds, but the car is continuing to move at high speed during this activity.  If PDK had a 0.3 laptime advantage for every shift, the PDK version of Porsche cars would be many seconds, if not MINUTES faster around the Nordschliefe than the manual version - instead there is a very small if any difference.

    You need to consider how much faster the PDK car is going due to avoiding the 0.3 shifting time (maybe 1kph, depending on speed). 

    If a manual car suddenly stopped in its tracks (infinitely faster than if the driver stood on the brakes during shifting) and then resumed his former speed after the shift, THEN there would be a 0.3 sec advantage for the PDK car.  Instead the manual car coninues to coast at high speed for this brief 0.3 sec shift and losing almost no speed (nor laptime).  There is a loss, but it is a tiny percent of the time it takes to shift.


    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello


    Re: GT3 RS 4.0

    If your assertion is true that there is little difference between PDK and manual time wise, why do most race and track cars use PDK or like versions for racing?Smiley


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    Re: GT3 RS 4.0

    nberry:

    If your assertion is true that there is little difference between PDK and manual time wise, why do most race and track cars use PDK or like versions for racing?Smiley

    Because in racing, a small difference is the difference between winning and losing.  0.3 sec per shift in racing would not be a small difference.  It would be an eternity!


    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello


    Re: GT3 RS 4.0

    There are probably hundreds of shifts on a lap of the Nordschliefe, so if each shift saved 0.01 sec, then it would save a couple sec per lap - a very positive result.  Now, 0.3 sec is 30 times more...


    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello


    Re: GT3 RS 4.0

    Grant, you are assuming all drivers are the same and failing to recognize that they are human and could not consistently during the duration of a race shift as fast as you say. I will acknowledge that a skilled driver can shift almost as fast as a computer but to do so regularly is beyond his/her ability.

     


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    Re: GT3 RS 4.0

    How am I failing to do that, Nick?  I conceded a racing advantage to PDK, even with perfect shifting.  But if someone is losing 0.3 sec per shift on average with a manual, maybe driving is the wrong hobby.  


    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello


    Re: GT3 RS 4.0

    Note:  to lose 0.3 sec of laptime per shift, the time to execute a shift would have to be several seconds...


    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello


    Re: GT3 RS 4.0

    Agreed. Smiley

    I haven't Googled it but I wonder whether test have been done to determine the difference in human shifting speed compared to computerized shifting. We know the speed of the computer but I suppose it would be difficult to time a human because of all the variables.


    --

     


    Re: GT3 RS 4.0

    RC:
    I am actually waiting for the first sports cars which adapt to the track they are driving on (based on a super accurate GPS position). Before and after every single curve, the car knows how to down- and/or upshift, this would be amazing (or boring...depending on the view Smiley).

    Good one.  Smiley  For a moment there, I actually thought you meant this - but then I realised that you couldn't possibly have been serious....could you?


    Re: GT3 RS 4.0

    Grant:

    There are probably hundreds of shifts on a lap of the Nordschliefe, so if each shift saved 0.01 sec, then it would save a couple sec per lap - a very positive result.  Now, 0.3 sec is 30 times more...

    A few hunderds is a bit too much. With my race Clio, I shift about 70 times on a clean lap.


    Re: GT3 RS 4.0

    Grant:
    nberry:

    If your assertion is true that there is little difference between PDK and manual time wise, why do most race and track cars use PDK or like versions for racing?Smiley

    Because in racing, a small difference is the difference between winning and losing.  0.3 sec per shift in racing would not be a small difference.  It would be an eternity!

    Based on times recorded at the Leipzig track 0.3s per shift could be a correct estimate IF:

    - the shifts are done at high speed (approx. 170kph in Leipzig)

    - and: the car is not equipped with the GT3RS4.0/GT2RS gear-box (which reduces the delay relative to PDK substantially).

    In Leipzig, we were able to calculate that 3 high-speed shifts on the 997GT2 Mk1 (i.e. not RS) reduced the lap time by approx. 0.9s per lap, i.e. 0.3s per shift. In a GT3RS 4.0 or GT2RS the disadvantage is probably closer to 0.1s per shift.


    Re: GT3 RS 4.0

    Grant:

    Note:  to lose 0.3 sec of laptime per shift, the time to execute a shift would have to be several seconds...

    Not at all - it depends on the speed you are traveling at. If - at high-speed shifts - another car with PDK continues to accelerate and your manual car "hits" the aerodynamic wall during a relatively short shift procedure the resulting loss in lap time can be quite large (see my above post) Smiley


    Re: GT3 RS 4.0

    So, you are claiming 7-10 sec per lap improvement at Nordschiefe for PDK?  If so, why have Porsche's official times never reflected this with Carrera and Cayman?  Certainly, they would benefit from the marketing of an expensive option...


    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello


    Re: GT3 RS 4.0

    Grant:

    So, you are claiming 7-10 sec per lap improvement at Nordschiefe for PDK?  If so, why have Porsche's official times never reflected this with Carrera and Cayman?  Certainly, they would benefit from the marketing of an expensive option...

    I don't know the difference on NBR. I only know what I wrote above - because these numbers (from Porsche's Leipzig track) I recorded myself Smiley BTW, the instructors were not surprised by the loss in lap time due to the manual shifts at higher speeds. They mentioned that the Turbo lag might also explain part of the problem.


    Re: GT3 RS 4.0

    Shifting a Turbo causes major turbo-lag - that I could agree with.  Don't quite believe .3 sec is possible with any other motor though.  I do agree that the higher the speed, the larger the time penalty though...

    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello


    Re: GT3 RS 4.0

    Grant is absolutely correct of course.  Shifting delay would not add directly to lap time, unless you were not traveling at all during that time, which is not typically the case.

    Using a video of the instrument cluster in some (fortunate) GT3RS4.0 driver's car during his efforts to drive from 0 to 300 kph just for the fun of it, I got some very rough acceleration and speed data and calculated the following fictitious example:

    A manual GT3RS4.0 and an imaginary PDK version run side-by-side, starting at 80mph in 3rd gear around 6320 rpm.  They both accelerate as fast as they can for the next 640 feet.

    While accelerating in 3rd from 80mph to 106mph both cars are identical.   They take approximately 2.04 seconds to reach 106mph, and travel around 280 feet.   Both cars are now pushing the rev limit around 8400 rpm.

    While shifting into 4th, the manual experiences a .3 second power delay, during which he continues at 106mph and travels almost 50 feet.  Then in 4th, the manual accelerates from 106 to 120 in approximately 1.88 seconds, and covers around 310 feet - a total run of 640 feet in 4.22 seconds.

    The GT3RS4.0 PDK has been accelerating continuously thanks to an instantaneous shift without power delay, has achieved a speed of 122 mph at the same location (640 feet) in 4.188 seconds.  The PDK wins, but the .3 second power delay has netted only a .032 second faster time, and a lead of just under 6 feet.

    Sorry if some of the numbers are off a little, but I did the best I could using some else's shaky video.  Unfortunately the exact performance specs for my GT3RS4.0 are the buried in owner's manual, locked up tight, in some one else's garage, several decades in the future.
     


    Re: GT3 RS 4.0

    Grant:

    Shifting a Turbo causes major turbo-lag - that I could agree with.  Don't quite believe .3 sec is possible with any other motor though.  I do agree that the higher the speed, the larger the time penalty though...

    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello

    The car we compared the GT2 with was a N/A 430 Scuderia, BTW.


    Re: GT3 RS 4.0

    davew (cincy):


    While shifting into 4th, the manual experiences a .3 second power delay, during which he continues at 106mph and travels almost 50 feet.  Then in 4th, the manual accelerates from 106 to 120 in approximately 1.88 seconds, and covers around 310 feet - a total run of 640 feet in 4.22 seconds.

    The GT3RS4.0 PDK has been accelerating continuously thanks to an instantaneous shift without power delay, has achieved a speed of 122 mph at the same location (640 feet) in 4.188 seconds.  The PDK wins, but the .3 second power delay has netted only a .032 second faster time, and a lead of just under 6 feet.
     

    Your calculation should also take into account the "aerodynamic" effect - i.e. the manual car will actually reduce its speed during the shifting procedure Smiley


    Re: GT3 RS 4.0

    Very true.  I'm not sure how much slowing occurs in a fraction of a second, but I'm sure you are at least right in principle!

    I also assumed constant acceleration in any given gear, (measured the overall time it took the tac to move from the previous gear's projected rpm up to 8400 rpm)  which, I'm sure is not the exact case, but close enough to make the point, I think.

    Another miniscule difference is that the PDK transmission probably has at least a little more rotating mass, and doesn't accelerate quite the same as the manual too.

    As an engineer, I love the idea of the PDK.  I think its impressive technology.

     


    Re: GT3 RS 4.0

    The part that is left out here is the deceleration segments. The faster you go, given equal brakes and suspension, the earlier you have to brake for a corner. Therefore, only part of the acceleration advantage is beneficial to the laptime.

    On the Nordschleife, several sweeping turns are taken at half throttle where the PDK box will only gain a small advantage.

    Re: GT3 RS 4.0

    davew (cincy):

    Very true.  I'm not sure how much slowing occurs in a fraction of a second, but I'm sure you are at least right in principle!

     

    The strange thing is that the car can loose like 5-10kph (!) during these high-speed shifts (relative to N/A car with F1 transmission) Smiley


    Re: GT3 RS 4.0

    Grant:
    nberry:

    If your assertion is true that there is little difference between PDK and manual time wise, why do most race and track cars use PDK or like versions for racing?Smiley

    Because in racing, a small difference is the difference between winning and losing.  0.3 sec per shift in racing would not be a small difference.  It would be an eternity!

    This shouldn't be the only reason. Before, during and after shifting, a couple of things can go wrong, so making the process easier/simpler actually benefits the driver and thus lap time a lot because the danger of an error (driver and hardware) is reduced. The attention a driver would need to use the clutch could be used for something else (of course in the sub-conscious but you get my point). So shifting time alone isn't really the only reason for the abandoning of "true" manual in professional racing.


    --

    RC (Germany) - Rennteam Editor Porsche Panamera Turbo S, Cayenne GTS (958), BMW X3 35d (2012), Mini Cooper S Countryman All4


    Re: GT3 RS 4.0

    Racing gearboxes have clutches.


    Re: GT3 RS 4.0

    MKSGR:
    davew (cincy):

    Very true.  I'm not sure how much slowing occurs in a fraction of a second, but I'm sure you are at least right in principle!

     

    The strange thing is that the car can loose like 5-10kph (!) during these high-speed shifts (relative to N/A car with F1 transmission) Smiley

    That number is based on the Turbocharged GT2 that falls out of maximum boost, right?  No way that happens with a normally aspirated motor...


    --

    73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs).  Former: 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550 Maranello


    Re: GT3 RS 4.0

    Ok, you convinced me to adjust for deceleration during the shift...

    If the manual car decelerates at 10 ft/s2 (this is comparable to the acceleration it has in 4th gear, so that's a lot of wind resistance!) it will loose around 3kph (around 2mph) during a .3 second shift.  It leaves 3rd gear around 106 mph, and enters 4th gear around 104.  That seems a little larger of a speed loss than I would expect, but I don't really watch the speedo that closely on the track - and I'm not sure the response time of it would allow for that accurate of a read in that short a period of time anyway.

    This actually lengthens my track from around 640 feet to 676 feet because the "finish line" I have defined previously was the point in the straight where the manual car hits 120mph, and the manual car takes a little longer to get there now...

    Result:  PDK car now wins by .08 seconds with a lead of around 10 feet at the new finish line. 

    That's a much larger result than I would have expected from one shift though.  I'd have to see better data on the deceleration rate around 100mph to make sure this is reasonable.

    One more thing does occur to me during all this, however.  PDK not only effectively removes the delay during the shift, but it also assures that you shift very near redline, without bumping the limiter.  I confess that my shifting on track is anything but perfect; and the biggest error I have is bumping on the limiter.  Of course that doesn't happen every time, but when it does, I'm sure it last for much longer than .3 seconds.  More experienced drivers can do this way better than me I'm afraid...

    edit:  RC made this very point a few post above.  Sorry RC...!


     
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