996TT vs. 997.1TT AWD system ?
06-15-2015, 12:10 PM
#2
Rocky Mountain High
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The 996 TT utilizes a mechanically controlled viscous coupling to drive the front wheels. The 997 TT utilizes an electronically controlled system to engage the front wheels. I think the 997 TT system is better and it actually drives the front wheels more frequently than the 996 TT system. The mechanical system in the 996 requires a speed differential between front and rear wheels in order to activate the viscous coupling. PSM frequently intervenes and negates wheel spin before the front wheels are ever engaged.
06-16-2015, 12:17 AM
#4
06-16-2015, 04:35 AM
#6
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996TT vs. 997.1TT AWD system ?
Really appreciate that document. Is it from the OEM compendium in the car, or another source?
06-16-2015, 07:54 AM
#7
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06-16-2015, 08:34 AM
#8
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06-16-2015, 10:40 AM
#9
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Porsche's chief test driver, Walter Rohrl, states that he "was not happy with the way the all-wheel-drive system was set up [in the 997.1 Turbo]....The differential was continuously adjusting torque split, which made the car change attitude frequently when oversteering. It was very nervous and difficult to drift clearly because of this--so [Rohrl] asked for a setup that was totally consistent and user friendly." In addition to suspension changes, Porsche engineers altered the manner in which the front differential distributes torque between the front and rear axles in the 997.2 Turbo. Ulrich Morbitzer, the 997.2 Turbo's chassis engineer, describes the change: "We introduced the Getrag front differential in the [997.1] Turbo....While this was an improvement over the ZF unit in the Carrera 4, we had feedback from customers and the press telling us it was not easy to drift the [997.1] Turbo. This was because the differential would continuously alter the torque split on a changing surface and confuse the driver, who could encounter understeer one second and oversteer the next. The fault lay not in the differential, which is simply a mechanical device that apportions the torque according to the ECU, which in turn takes cues from sensors....The problem was actually the logic in the ECU mapping. The logic was absolute. It would send a certain percentage of torque to the front axle under certain conditions. That has been changed in the [997.2 Turbo] to mimic a viscous clutch, which progressively and seamlessly apportions exactly the torque required to the front axle" (Ian Kuah, "More than Meets the Eye," Excellence, December 2009).
Last edited by Doc V.; 06-16-2015 at 12:22 PM. Reason: publication date error
06-16-2015, 10:51 AM
#10
Drifting
Porsche did not change the AWD system in the 997.2 Turbo (which Porsche occasionally identifies as the 997.5 Turbo) to accommodate the PDK transmission. Instead, changes in the 997.2 Turbo's AWD system followed from complaints about the handling characteristics of the 997.1 Turbo.
Porsche's chief test driver, Walter Rohrl, states that he "was not happy with the way the all-wheel-drive system was set up [in the 997.1 Turbo]....The differential was continuously adjusting torque split, which made the car change attitude frequently when oversteering. It was very nervous and difficult to drift clearly because of this--so [Rohrl] asked for a setup that was totally consistent and user friendly." In addition to suspension changes, Porsche engineers altered the manner in which the front differential distributes torque between the front and rear axles in the 997.2 Turbo. Ulrich Morbitzer, the 997.2 Turbo's chassis engineer, describes the change: "We introduced the Getrag front differential in the [997.1] Turbo....While this was an improvement over the ZF unit in the Carrera 4, we had feedback from customers and the press telling us it was not easy to drift the [997.1] Turbo. This was because the differential would continuously alter the torque split on a changing surface and confuse the driver, who could encounter understeer one second and oversteer the next. The fault lay not in the differential, which is simply a mechanical device that apportions the torque according to the ECU, which in turn takes cues from sensors....The problem was actually the logic in the ECU mapping. The logic was absolute. It would send a certain percentage of torque to the front axle under certain conditions. That has been changed in the [997.2 Turbo] to mimic a viscous clutch, which progressively and seamlessly apportions exactly the torque required to the front axle" (Ian Kuah, "More than Meets the Eye," Excellence, December 2000).
Porsche's chief test driver, Walter Rohrl, states that he "was not happy with the way the all-wheel-drive system was set up [in the 997.1 Turbo]....The differential was continuously adjusting torque split, which made the car change attitude frequently when oversteering. It was very nervous and difficult to drift clearly because of this--so [Rohrl] asked for a setup that was totally consistent and user friendly." In addition to suspension changes, Porsche engineers altered the manner in which the front differential distributes torque between the front and rear axles in the 997.2 Turbo. Ulrich Morbitzer, the 997.2 Turbo's chassis engineer, describes the change: "We introduced the Getrag front differential in the [997.1] Turbo....While this was an improvement over the ZF unit in the Carrera 4, we had feedback from customers and the press telling us it was not easy to drift the [997.1] Turbo. This was because the differential would continuously alter the torque split on a changing surface and confuse the driver, who could encounter understeer one second and oversteer the next. The fault lay not in the differential, which is simply a mechanical device that apportions the torque according to the ECU, which in turn takes cues from sensors....The problem was actually the logic in the ECU mapping. The logic was absolute. It would send a certain percentage of torque to the front axle under certain conditions. That has been changed in the [997.2 Turbo] to mimic a viscous clutch, which progressively and seamlessly apportions exactly the torque required to the front axle" (Ian Kuah, "More than Meets the Eye," Excellence, December 2000).
06-16-2015, 11:29 AM
#11
Rocky Mountain High
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Very interesting.
06-21-2015, 09:01 PM
#12
Nordschleife Master
This is why I prefer the old mechanical system. It was essential rwd all the time and the only times that front wheel drive kicks in is under please save me conditions. It's a great thing to have a last resort, even though there is a weight penalty due to the front diff but then again, that added weight to a all ready light front end in a rear engined car, I would not want awd on all the time.
06-21-2015, 09:47 PM
#13
Rennlist Member
Porsche did not change the AWD system in the 997.2 Turbo (which Porsche occasionally identifies as the 997.5 Turbo) to accommodate the PDK transmission. Instead, changes in the 997.2 Turbo's AWD system followed from complaints about the handling characteristics of the 997.1 Turbo.
Porsche's chief test driver, Walter Rohrl, states that he "was not happy with the way the all-wheel-drive system was set up [in the 997.1 Turbo]....The differential was continuously adjusting torque split, which made the car change attitude frequently when oversteering. It was very nervous and difficult to drift clearly because of this--so [Rohrl] asked for a setup that was totally consistent and user friendly." In addition to suspension changes, Porsche engineers altered the manner in which the front differential distributes torque between the front and rear axles in the 997.2 Turbo. Ulrich Morbitzer, the 997.2 Turbo's chassis engineer, describes the change: "We introduced the Getrag front differential in the [997.1] Turbo....While this was an improvement over the ZF unit in the Carrera 4, we had feedback from customers and the press telling us it was not easy to drift the [997.1] Turbo. This was because the differential would continuously alter the torque split on a changing surface and confuse the driver, who could encounter understeer one second and oversteer the next. The fault lay not in the differential, which is simply a mechanical device that apportions the torque according to the ECU, which in turn takes cues from sensors....The problem was actually the logic in the ECU mapping. The logic was absolute. It would send a certain percentage of torque to the front axle under certain conditions. That has been changed in the [997.2 Turbo] to mimic a viscous clutch, which progressively and seamlessly apportions exactly the torque required to the front axle" (Ian Kuah, "More than Meets the Eye," Excellence, December 2009).
Porsche's chief test driver, Walter Rohrl, states that he "was not happy with the way the all-wheel-drive system was set up [in the 997.1 Turbo]....The differential was continuously adjusting torque split, which made the car change attitude frequently when oversteering. It was very nervous and difficult to drift clearly because of this--so [Rohrl] asked for a setup that was totally consistent and user friendly." In addition to suspension changes, Porsche engineers altered the manner in which the front differential distributes torque between the front and rear axles in the 997.2 Turbo. Ulrich Morbitzer, the 997.2 Turbo's chassis engineer, describes the change: "We introduced the Getrag front differential in the [997.1] Turbo....While this was an improvement over the ZF unit in the Carrera 4, we had feedback from customers and the press telling us it was not easy to drift the [997.1] Turbo. This was because the differential would continuously alter the torque split on a changing surface and confuse the driver, who could encounter understeer one second and oversteer the next. The fault lay not in the differential, which is simply a mechanical device that apportions the torque according to the ECU, which in turn takes cues from sensors....The problem was actually the logic in the ECU mapping. The logic was absolute. It would send a certain percentage of torque to the front axle under certain conditions. That has been changed in the [997.2 Turbo] to mimic a viscous clutch, which progressively and seamlessly apportions exactly the torque required to the front axle" (Ian Kuah, "More than Meets the Eye," Excellence, December 2009).
06-21-2015, 10:04 PM
#14
Rennlist Member
A far more complicated (and expensive) AWD system with sensors, computers, and adjustable clutches being redesigned to mimic the characteristics inherent in the 996's simple viscous coupling.
06-22-2015, 12:06 AM
#15
I wouldn't worry about 997.1 to 997.2 specs... They generally release the same PR stuff to make the latest and greatest seem revolutionary & how did anyone handle the previous car without -- -insert some P-car talk..normally 3-4 words.
I remember the salesman saying this and I said easy you'll be repeating the same thing about this car in a couple of years.
I remember the salesman saying this and I said easy you'll be repeating the same thing about this car in a couple of years.