Owners of both 997 TURBO & 996 TURBO
#16
09-25-2010 | 04:38 AM
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I'm not sure I believe that. I know it's been beaten to death on RL and RT, but the fact is the 40+ second runs for both cars were done on completely different days and different tracks.
Every side by side run shows that the new turbo keeps up with the GT2, (which ran a 36 second 0-300 km/h.)
Every side by side run shows that the new turbo keeps up with the GT2, (which ran a 36 second 0-300 km/h.)
#17
09-25-2010 | 07:11 PM
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I know that Sport mode on will bring more power to rear, just wonder what that number is (hopefully a lot more than 60%). TIA.
#20
10-10-2010 | 10:59 AM
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...
In comparison to the older viscous coupling system on the 996TT, the 997TT multi plate clutch is capable of transfering 80 to 100% of the torque instantaneously from rear to front. This allows delivery of as much as 100% drive power to be transferred to either axle during slip...(although on a dry road under constant throttle, it send 60 percent of the power to the rear axle.) The 996tt viscous coupling (like the 993) is limited in the amount of torque it can transfer to the front...I've read as little as 50 foot pounds of torque is transferred to the front.
In comparison to the older viscous coupling system on the 996TT, the 997TT multi plate clutch is capable of transfering 80 to 100% of the torque instantaneously from rear to front. This allows delivery of as much as 100% drive power to be transferred to either axle during slip...(although on a dry road under constant throttle, it send 60 percent of the power to the rear axle.) The 996tt viscous coupling (like the 993) is limited in the amount of torque it can transfer to the front...I've read as little as 50 foot pounds of torque is transferred to the front.
Is it possible to tune or adjust the bias ourselves in TT?
Last edited by muifast; 10-10-2010 at 12:16 PM.
#21
10-10-2010 | 02:08 PM
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Are you referring to .1TT or .2TT? I may be wrong and I am not sure what was changed in the 4wd system, but in one of the reviews of .2TT with Walter Rohrl, they had mentioned that torque split was reduced to the front to induce a more consistent rear bias during dry performance.
Is it possible to tune or adjust the bias ourselves in TT?
Is it possible to tune or adjust the bias ourselves in TT?
You are correct, the algorithm for the 4wd system was changed from 997.1 to 997.2. Not only is 997.2 more rearward bias overall, in a curve the transition between the front and rear bias, at high speed all out driving if I read between the lines correctly, is also "improved" (less abrupt). (Whether this change could ever be sensed by an amateur driver is up for debate though.)
Anyway/however, the change is not just software; 997.2 has stiffer springs and sway bar as well.
I am sure the bias could be adjusted if Porsche wants to, but outside of an OEM release, it's either too complicated and too dangerous to adjust. IMHO: The adjustment would require both a software guy and a chassis test driver -- something that no third party has attempted, probably for lack of potential $$ gain, or expertise, or both.
#23
10-17-2010 | 06:15 PM
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Hi Bob, would you please look to see if service manual says anything about: Same condition of dry road & constant throttle, but with the Sport mode on?
I know that Sport mode on will bring more power to rear, just wonder what that number is (hopefully a lot more than 60%). TIA.
I know that Sport mode on will bring more power to rear, just wonder what that number is (hopefully a lot more than 60%). TIA.
I'm embarrassed to say that I can not find my source (the 60% number.) I have flipped through my 997TT service tech manual and couldn't find it referenced...
I'll have to dig deeper...the number sticks out in my mind for some reason, but I wish I could quote you the source.
- bob
#24
10-18-2010 | 12:51 AM
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By having a look at 996TT thread about ICs of 997,2 test,we can see great differences in IAT between these two ICs...(997,1 and 997,2)Perhaps this is a reason for these differences in performance between these two cars...20hp difference cant tell that difference...But 20c of IAT difference at same conditions can help 997.2TT be much faster than 997,1TT...
#25
10-18-2010 | 01:43 AM
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I was kind of surprised as well, but that's what I thought I read in my service info book on the 997TT, Chad's KA thread, and a few Porsche history books.
My understanding is that the the AWD system used in the 964 had a multi plate clutch. The differential normally sent 31% to the front axle and 69% to the rear. The rear differential also incorporated a similar clutch acting as a limited slip differential. The clutch was controlled by the computer and ABS sensors for each individual wheel. It was criticized as being over-corrective of the tail-happy 911, creating understeer.
Then Porsche changed it's design radically, and moved to a viscous coupling LSD. To make the viscous coupling system engaged in the front, Porsche made the rear wheel/tire diameter smaller, causing a small speed difference between the drive shafts in the front and rear. The viscous liquid normally transferred 5-15% torque to the front axle (which was much less than the 964.) If conditions were necessary, the viscous coupling LSD could send 100% torque to the other axle.
I think the 996 and 993 AWD viscous coupling designs are very similar, and a limited amount of torque can be transferred to the front.
With the 997, Porsche came full circle back to what is essentially a multi plate design.
My understanding is that the the AWD system used in the 964 had a multi plate clutch. The differential normally sent 31% to the front axle and 69% to the rear. The rear differential also incorporated a similar clutch acting as a limited slip differential. The clutch was controlled by the computer and ABS sensors for each individual wheel. It was criticized as being over-corrective of the tail-happy 911, creating understeer.
Then Porsche changed it's design radically, and moved to a viscous coupling LSD. To make the viscous coupling system engaged in the front, Porsche made the rear wheel/tire diameter smaller, causing a small speed difference between the drive shafts in the front and rear. The viscous liquid normally transferred 5-15% torque to the front axle (which was much less than the 964.) If conditions were necessary, the viscous coupling LSD could send 100% torque to the other axle.
I think the 996 and 993 AWD viscous coupling designs are very similar, and a limited amount of torque can be transferred to the front.
With the 997, Porsche came full circle back to what is essentially a multi plate design.
my 996tt will still be my true love
#26
10-18-2010 | 08:50 AM
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Having recently changed froman X50 996 TT to a 997 TT....I can tell you both are bullet proof DD with plenty of power and great road manners...
However the 997 is much smoother and more refined and I am very happy with the change.
However the 997 is much smoother and more refined and I am very happy with the change.
#28
10-18-2010 | 01:20 PM
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drove my 996tt today it felt a little out dated. 996tt seems to use better materials, i still enjoy driving her. u work a little harder than the 997tt. more drivers skill is involve.
i love both of them either way. my only regret is when i sold my 993tt
i love both of them either way. my only regret is when i sold my 993tt
#29
10-18-2010 | 05:25 PM
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Can...sorry I didn't get back to you sooner. Didn't see your post.
I'm embarrassed to say that I can not find my source (the 60% number.) I have flipped through my 997TT service tech manual and couldn't find it referenced...
I'll have to dig deeper...the number sticks out in my mind for some reason, but I wish I could quote you the source.
- bob
I'm embarrassed to say that I can not find my source (the 60% number.) I have flipped through my 997TT service tech manual and couldn't find it referenced...
I'll have to dig deeper...the number sticks out in my mind for some reason, but I wish I could quote you the source.
- bob