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And if that was your second choice I’d love to see your first!!
Originally Posted by Type65
Thanks! The purchase did go through! It is the second Porsche I have bought from a Rennlist member and the seller was great! The car exceeded expectations! And even at $10k more than the 996 I almost bought 4 years ago, I feel like I got a better deal today! I love the car and couldn't be happier! Aside from being my second choice of color, which I still love arena red, it is exactly how I would have ordered it from the factory! It is an early 99 (3/98) with LSD, Sport Seats, and M030, as well as a rebuilt engine to 3.6L with LN Nickies, IMS, and plenty of other upgrades! It'll be my daily for now, but after driving a few hundred miles in it I almost wish I didn't have my 951 track car! This is my first 911, and it is incredible!
!
Gonna hijack my own thread temporarily and cross post something from the 997 forum because I'm curious what people here think of this, especially those with advanced Porsche technical knowledge. There has been a rumor/urban legend for sometime that Porsche engineers built in an undisclosed trick that allows 997.2 4s PDK cars to seamlessly convert from AWD to RWD by simply engaging the handbrake 1 click in certain modes. Though discussed and ridiculed often, nobody had posted anything definitive until this was posted a few days ago. Just curious what people think of this since I know there is ample discussion of AWD to RWD conversions in this and other forums.
Default 997.2 C4S to 2WD using cockpit controls2011 C4S PDK w/Sport Chrono
AWD to 2WD (rear) using cockpit controls
PDK gear shift in Auto versus Manual setting
I was able to get the front wheels disengaged (2WD rear) using the handbrake up one click (Video 1:42):
Sport Plus: ON
Stability Mgmt (PSM): OFF
Handbrake up one click
(Left PASM alone - in this case car turns it ON with Sport Plus)
Wow, that’s cool. But I’d like to see it in action at a little higher speed. I mean it work at a crawl, but will it work at 20 or 40mph.
And it might be obvious, but the handbrake, if it’s anything like the mechanical handbrake of the 996, should be adjusted so that nothing engages at one click. The brake should be slacked out.
If it’s easy to disengage from 4wd to 2wd, then I wish Porsche would have included that as an option, like a button.
Wow, that’s cool. But I’d like to see it in action at a little higher speed. I mean it work at a crawl, but will it work at 20 or 40mph.
And it might be obvious, but the handbrake, if it’s anything like the mechanical handbrake of the 996, should be adjusted so that nothing engages at one click. The brake should be slacked out.
If it’s easy to disengage from 4wd to 2wd, then I wish Porsche would have included that as an option, like a button.
Having it work only in Sport+ mode/fully automatic and PSM Off, where all shifts are taken to redline would be quite the ride if truly RWD. @Porschetech3 any thoughts on this?
Last edited by Optionman1; 01-29-2022 at 12:11 PM.
Gonna hijack my own thread temporarily and cross post something from the 997 forum because I'm curious what people here think of this, especially those with advanced Porsche technical knowledge. There has been a rumor/urban legend for sometime that Porsche engineers built in an undisclosed trick that allows 997.2 4s PDK cars to seamlessly convert from AWD to RWD by simply engaging the handbrake 1 click in certain modes. Though discussed and ridiculed often, nobody had posted anything definitive until this was posted a few days ago. Just curious what people think of this since I know there is ample discussion of AWD to RWD conversions in this and other forums.
That is definitely very interesting. And I am curious about what mechanical technology allows this. For example the VC isn't electrically controlled, is there some type of clutch or gearing in the PDK that allows the front wheel driveshaft to be disconnected from power?
And it might be obvious, but the handbrake, if it’s anything like the mechanical handbrake of the 996, should be adjusted so that nothing engages at one click. The brake should be slacked out.
The objective isn't to operate the brakes, the objective is to operate the switch that tells the car the handbrake lever has been moved. A weird sort of morse code if you will.
Just to add to what others have already said, this trick would be of no benefit and could not be used on the 996 series.
On the 996 series the AWD front/rear shafts are coupled with a mechanical vicious clutch. If the shaft speeds are the same, no power is transferred to the front drive, as the rear shaft speed gets faster then the front shaft ( rear wheel spin) , the Viscous fluid in the unit transfers torque to the front shaft. The higher the difference in speed the more torque is transferred. It is self controlling.
On the 997 series the AWD front/rear shafts are coupled with an electro-magnetic clutch. It is computer controlled and not dependent on shafts speeds, just dependent on programmed commands . That's why a trick like this can work on 997 series but not on 996 series.
Originally Posted by Optionman1
Having it work only in Sport+ mode/fully automatic and PSM Off, where all shifts are taken to redline would be quite the ride if truly RWD. @Porschetech3 any thoughts on this?
Originally Posted by 911Syncro
That is definitely very interesting. And I am curious about what mechanical technology allows this. For example the VC isn't electrically controlled, is there some type of clutch or gearing in the PDK that allows the front wheel driveshaft to be disconnected from power?
Originally Posted by theprf
997's have an electromagnetic center coupler, not the viscous clutch of previous AWD generations.
Ive always heard 15% power to front axle by default and more based on viscous clutch? Are you saying it’s actually zero (on dry pavement for ex)???
Originally Posted by Porschetech3
Just to add to what others have already said, this trick would be of no benefit and could not be used on the 996 series.
On the 996 series the AWD front/rear shafts are coupled with a mechanical vicious clutch. If the shaft speeds are the same, no power is transferred to the front drive, as the rear shaft speed gets faster then the front shaft ( rear wheel spin) , the Viscous fluid in the unit transfers torque to the front shaft. The higher the difference in speed the more torque is transferred. It is self controlling.
On the 997 series the AWD front/rear shafts are coupled with an electro-magnetic clutch. It is computer controlled and not dependent on shafts speeds, just dependent on programmed commands . That's why a trick like this can work on 997 series but not on 996 series.
The coupling on the 996 AWD is a Fluid Coupling, meaning nothing touches anything inside but the viscous fluid. And when nothing inside moves no torque is transmitted.
It would be like sticking both your hands in opposite sides of a tub full of grease, as long as your hands remain still, no pressure will be exerted anywhere in the tub.
In actual use on a 996 AWD, there is always some difference in the speed of the front/rear shafts with the rear tires being slightly smaller ( 295/30/18 vs 225/40/18) . ( rear tires are always spinning slightly faster)This creates a small torque being applied to the front drive, and will increase dramatically as the rear tires wear faster than the front. This is the reason the tires should be replaced as a set on AWD, if the rear tires are worn completely out and the front tires are new, the difference will be so great that the viscous clutch will be overworked and overheated.. The viscous clutch is only designed to put a small torque on the front drive, and more if NEEDED , not to over-worked.
Originally Posted by bdronsick
Ive always heard 15% power to front axle by default and more based on viscous clutch? Are you saying it’s actually zero (on dry pavement for ex)???
Originally Posted by pulpo
I've always heard 5%
Last edited by Porschetech3; 01-29-2022 at 07:59 PM.
01-29-2022, 08:42 AM
