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    Mechanical differential lock with manual shift only

    As I understood from the web presentation the 997 turbo will be offered with an optional mechanical differential lock with manual shift only. So for those who are going with tiptronic shift, would you sacrifice the mechanical differential lock for a bit of performance that might be picked up by a manual with mechanical differential lock? especially on non straight line performance?

    Re: Mechanical differential lock with manual shift only

    I would NEVER choose tiptronic over manual with LSD for a sports car (even if Tip is slightly faster in a drag race). I realize that the TT is already close to a GT car, but with a Tip it is REALLY a GT car instead of a sports car, imho.

    Re: Mechanical differential lock with manual shift only

    Quote:
    rfakhri said:
    As I understood from the web presentation the 997 turbo will be offered with an optional mechanical differential lock with manual shift only. So for those who are going with tiptronic shift, would you sacrifice the mechanical differential lock for a bit of performance that might be picked up by a manual with mechanical differential lock? especially on non straight line performance?



    Would you please elaborate the advantage of LSD in a AWD car for me? Have you seen the specs of the new electronically controlled AWD system for the 997 Turbo?

    To take advantage of that "extra" (LSD), you need to be the hell of a driver, otherwise it won't help anything since the AWD on the 997 Turbo is so advanced and traction isn't really a problem.

    Re: Mechanical differential lock with manual shift only

    AFAIK the rear LSD will give the 997TT a sportier handling through the curves.

    The reason being that with 480HP on tap, when you spin one of the rear tires accelerating out of a curve, if you don't have a rear LSD the AWD will need to necesarily send torque to the front wheels to compenmsate.

    However if you have a rear LSD, if you spin one wheel faster than the other to a certain extent (depending on the lock of the diff) the LSD with shift torque to the other wheel therefore maintaining grip and stability and avoiding torque being needed to be sent to the front axle as much, giving a more RWD character in its handling (less understeer and better steering feedback since the front wheels won't be needed to be drive as much).

    How much that will be notieable on sporty street driving? I have no clue but I would love to test both to compare

    The other cars with active diferentials like the Lancer EVO and Subaru Impreza have rear diferentials as well, but as standard.

    Re: Mechanical differential lock with manual shift only

    Can someone help me with my dilema then. I have the option to buy a July launch car, however, when we (dealer and I) speced the car neither was aware of the LSD option. My car is otherwise just how I want it. I'd appreciate your valued opinions re: if you think I should take the car without LSD or wait for a later build. I am on another list. Could probably have another car within six months.
    Artic silver
    Black leather
    Sport chrono turbo
    Sport shifter (Manual, of course )
    Porsche crests headrests
    PDC

    Re: Mechanical differential lock with manual shift only

    Quote:
    Carlos from Spain said:


    However if you have a rear LSD, if you spin one wheel faster than the other to a certain extent (depending on the lock of the diff) the LSD with shift torque to the other wheel therefore maintaining grip and stability and avoiding torque being needed to be sent to the front axle as much, giving a more RWD character in its handling (less understeer and better steering feedback since the front wheels won't be needed to be drive as much).




    Thank you for simple explanation. I always wondered what LSD did. Looks like even the 997TT can benefit from it.

    Re: Mechanical differential lock with manual shift only

    Quote:
    RC said:
    Would you please elaborate the advantage of LSD in a AWD car for me? Have you seen the specs of the new electronically controlled AWD system for the 997 Turbo?

    To take advantage of that "extra" (LSD), you need to be the hell of a driver, otherwise it won't help anything since the AWD on the 997 Turbo is so advanced and traction isn't really a problem.


    RC - The advantage here will not be in traction (putting power to the road) as much as it will provide more stability under braking and turning. A clutch LSD really affects the handling characteristics of a rear-engined car alot under braking and turning, so that you can brake later and enter a turn faster without the rear getting loose. I like it alot more for this reason (even more than the added traction on the power, which I admit is just gravy when you have AWD and PTM).

    People who added LSD to the last of the 996TT's reported a very nice improvement, even though this car had PSM and pretty decent traction too.

    The main advantage of a clutch LSD over a torque-biasing diff (like Quaife) is the stability it gives on the brakes or in a turn. If Porsche only cared about traction, then all their cars would use a Quaife type diff which never wears out and doesn't interfere with PSM (does no locking under braking, so PSM could brake each wheel independently). Obviously, Porsche engineers value this aspect of a clutch LSD so much, they stayed with it in all their cars with LSD available (GT2/3/CGT/TT/997 with -20mm). The locking ratios in the TT and 997 are reduced to work with PSM, but at least they didn't change to Quaife type...

    Re: Mechanical differential lock with manual shift only

    A car with an open differential can only provide traction control with brakes. So when your inside rear wheel slips, the car will brake the inside rear wheel and cut the engine power in order to transfer the torque to the outside wheel. A limited-slip differential can transfer the torque from one side to the other under full power (ie., without braking or reducing engine power). It also tends to react quicker than an open differential w/ brakes. So a car with an LSD will have a big performance advantage in a corner where one of your wheels looses grip.

    Re: Mechanical differential lock with manual shift only

    Quote:
    hatchback said:
    A car with an open differential can only provide traction control with brakes. So when your inside rear wheel slips, the car will brake the inside rear wheel and cut the engine power in order to transfer the torque to the outside wheel. A limited-slip differential can transfer the torque from one side to the other under full power (ie., without braking or reducing engine power). It also tends to react quicker than an open differential w/ brakes. So a car with an LSD will have a big performance advantage in a corner where one of your wheels looses grip.


    I think this effect is minimized with AWD and PTM, since PTM will electronically apportion power to the front axle, until the rear wheel stops spinning. It won't be as good as LSD on the power, but close. I still believe the bigger difference will come with handling in the corners and under braking. But, LSD is probably better on the power too for the reasons you and Carlos mentioned.

    I cannot imagine taking Tip without LSD, unless this is a daily driver, you face alot of traffic in your city, and you don't like shifting much...

    Re: Mechanical differential lock with manual shift only

    Quote:
    Grant said:
    Quote:
    hatchback said:
    A car with an open differential can only provide traction control with brakes. So when your inside rear wheel slips, the car will brake the inside rear wheel and cut the engine power in order to transfer the torque to the outside wheel. A limited-slip differential can transfer the torque from one side to the other under full power (ie., without braking or reducing engine power). It also tends to react quicker than an open differential w/ brakes. So a car with an LSD will have a big performance advantage in a corner where one of your wheels looses grip.


    I think this effect is minimized with AWD and PTM, since PTM will electronically apportion power to the front axle, until the rear wheel stops spinning. It won't be as good as LSD on the power, but close. I still believe the bigger difference will come with handling in the corners and under braking. But, LSD is probably better on the power too for the reasons you and Carlos mentioned.

    I cannot imagine taking Tip without LSD, unless this is a daily driver, you face alot of traffic in your city, and you don't like shifting much...



    I'll take an Audi or a Benz for a daily, thank you .
    I don't get it. If you face such horrendous traffic on your way to work and back, that you need an auto tranny, why use a sports car as your transportation in the first place?

    Re: Mechanical differential lock with manual shift only

    Quote:
    Crash said:
    Quote:
    Grant said:
    Quote:
    hatchback said:
    A car with an open differential can only provide traction control with brakes. So when your inside rear wheel slips, the car will brake the inside rear wheel and cut the engine power in order to transfer the torque to the outside wheel. A limited-slip differential can transfer the torque from one side to the other under full power (ie., without braking or reducing engine power). It also tends to react quicker than an open differential w/ brakes. So a car with an LSD will have a big performance advantage in a corner where one of your wheels looses grip.


    I think this effect is minimized with AWD and PTM, since PTM will electronically apportion power to the front axle, until the rear wheel stops spinning. It won't be as good as LSD on the power, but close. I still believe the bigger difference will come with handling in the corners and under braking. But, LSD is probably better on the power too for the reasons you and Carlos mentioned.

    I cannot imagine taking Tip without LSD, unless this is a daily driver, you face alot of traffic in your city, and you don't like shifting much...



    I'll take an Audi or a Benz for a daily, thank you .
    I don't get it. If you face such horrendous traffic on your way to work and back, that you need an auto tranny, why use a sports car as your transportation in the first place?



    Couple reasons....one, for those on a "budget", much cheaper to just have a 997TT Tip as only car (daily driver and wkend toy) vs having both 997TT manual and S-Class (or other equally safe/comfortable auto tranny car) to fulfill both needs.

    Second, having become accustomed to steering precision/chassis dynamics/brake pedal feel/traction of 996TTS, I simply don't feel very safe driving an S-Class/CL (or any other sedan/SUV), even at <90MPH, b/c of their notably weaker, less confidence-inspiring active safety attributes....

    997TT Tip is simply world's best car IMO...arguably world's best real-world/all-weather performance, safety, convenience/comfort of auto and infreq mtce in one awfully cheap package

    Re: Mechanical differential lock with manual shift only

    Quote:
    997TT Tip is simply world's best car IMO...arguably world's best real-world/all-weather performance, safety, convenience/comfort of auto and infreq mtce in one awfully cheap package



    For your purpose you are absolutely correct

    Re: Mechanical differential lock with manual shift only

    It may sound as a stupid question, but why Porsche doesn't offer LSD with tip?

    Re: Mechanical differential lock with manual shift only

    Quote:
    Ziggy said:
    It may sound as a stupid question, but why Porsche doesn't offer LSD with tip?



    Maybe they wanted to show some mercy to the 6-sp manual owners.

    Re: Mechanical differential lock with manual shift only

    So, I'll ask again. Would you take delivery of a 6spd. tt without lsd or wait for another one?

    Re: Mechanical differential lock with manual shift only

    Quote:
    devo said:
    So, I'll ask again. Would you take delivery of a 6spd. tt without lsd or wait for another one?


    I'd wait for LSD if you intend to put the car on a track or drive it very hard in the mountains often...

    Re: Mechanical differential lock with manual shift only

    Thanks.

    Re: Mechanical differential lock with manual shift only

    I'm with Grant without a doubt as well, but thats such a personal choice that only you can answer.

    Re: Mechanical differential lock with manual shift only

    Quote:
    devo said:
    So, I'll ask again. Would you take delivery of a 6spd. tt without lsd or wait for another one?



    Manual? Always with LSD if possible.

    Re: Mechanical differential lock with manual shift only

    Will probably never track the car. I do drive hard in the twisties or at least I think I do. I don't really know if I'll really appreciate the (LSD) diff's real benefit, however, it would be great to know it was there.
    Thanks for the opinions.

    Re: Mechanical differential lock with manual shift only

    Quote:
    RC said:
    Quote:
    rfakhri said:
    As I understood from the web presentation the 997 turbo will be offered with an optional mechanical differential lock with manual shift only. So for those who are going with tiptronic shift, would you sacrifice the mechanical differential lock for a bit of performance that might be picked up by a manual with mechanical differential lock? especially on non straight line performance?



    Would you please elaborate the advantage of LSD in a AWD car for me? Have you seen the specs of the new electronically controlled AWD system for the 997 Turbo?

    To take advantage of that "extra" (LSD), you need to be the hell of a driver, otherwise it won't help anything since the AWD on the 997 Turbo is so advanced and traction isn't really a problem.



    That makes sense. But the problem is that I'm trying to find reasons for those who dont like Tiptronic to stay with manual.

    Man . . . I tried Tiptronic on various porsches (none turbo) and just cant make myself like it. I guess personally shouldn't be too bothered at this stage cause I'm getting a Cayman S . . . should do work on liking it until I get there

    Re: Mechanical differential lock with manual shift only

    Quote:
    Grant said:
    Quote:
    hatchback said:
    A car with an open differential can only provide traction control with brakes. So when your inside rear wheel slips, the car will brake the inside rear wheel and cut the engine power in order to transfer the torque to the outside wheel. A limited-slip differential can transfer the torque from one side to the other under full power (ie., without braking or reducing engine power). It also tends to react quicker than an open differential w/ brakes. So a car with an LSD will have a big performance advantage in a corner where one of your wheels looses grip.


    I think this effect is minimized with AWD and PTM, since PTM will electronically apportion power to the front axle, until the rear wheel stops spinning. It won't be as good as LSD on the power, but close. I still believe the bigger difference will come with handling in the corners and under braking. But, LSD is probably better on the power too for the reasons you and Carlos mentioned.

    I cannot imagine taking Tip without LSD, unless this is a daily driver, you face alot of traffic in your city, and you don't like shifting much...



    Yes, the 996 Turbo without LSD does have pretty good traction on power. You hardly see any one sided wheel spinning situation. Actually, all 911 have very good traction on power even without LSD. You seem to see more wheel spinning on a boxster than a 996.

    Having said that, when compare to the GT2/GT3/Gt3RS with LSD, the cornering ability is light years ahead, apart from the obvious difference in suspension setting and weight. You are able to brake much later and on full throttle even before hitting the apex with so much traction. Going from full brake to full power in 0.5 sec. Where as in the Turbo, you have to brake very early and slowly feed in the power to ensure full power is efficiently transfer from the tyres to the ground. From full braking to full power takes around 1.2 sec.

    The LSD does transfer the turbo with open diff to a more sporty and responsive character. It does benefit both on the braking and acceleration side from my experience.

    Re: Mechanical differential lock with manual shift only

    At my persistence, my dealer was able to update my tt order to add the mech. diff. lock Thanks for your input. Car has a build date in April.

    Re: Mechanical differential lock with manual shift only

    Quote:
    devo said:
    At my persistence, my dealer was able to update my tt order to add the mech. diff. lock Thanks for your input. Car has a build date in April.



    Re: Mechanical differential lock with manual shift only

    Quote:
    devo said:
    At my persistence, my dealer was able to update my tt order to add the mech. diff. lock Thanks for your input. Car has a build date in April.


    April build? So you must have a launch car? correct?

    Re: Mechanical differential lock with manual shift only

    Quote:
    devo said:
    At my persistence, my dealer was able to update my tt order to add the mech. diff. lock Thanks for your input. Car has a build date in April.


    That's great news. Should be a sweet ride!

    Re: Mechanical differential lock with manual shift only

    Yes a launch car.

    Re: Mechanical differential lock with manual shift only

    Had to spec the car a few weeks ago. Was told then to use the 997 C4S and 996tt spec sheet. Anyway got the car I want. Might have made some subtle changes if I had the current spec. sheet but I don't believe that I'm missing anything important. Artic silver, Sport shifter, Sport chrono turbo, PDC, Crests in headrests, Wheel crests. Told there's optional Bose; only 9speaker. And of course, mech. diff. lock. Oh, and floormatts.

    Re: Mechanical differential lock with manual shift only

    Meant to post that I was told that there is NO optional Bose.

    Re: Mechanical differential lock with manual shift only

    I originally had spec'd LRD on my TT. However, I just returned from PDE in Birmingham, Alabama where I discussed this option with one of the instructors (professional race driver). He said that LRD wasn't not necessary as along as you weren't going to race the car on a track. Otherwise, he said, you would probably rarely, if ever use LRD and that the other PSM features on the car would be more than sufficient.

     
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