POSTING this from the 997 Forum thread :

I think the feature is only on the pdk equipped c4 and c4s. I couldn't find any followup on the turbos.

The affect was nearly identical to the 991 c2s I test drove. Nearly the same slipping. So it begs a question : Why did the Engineers create this feature ?

Any c4s 991 drivers attempt the disengagement ?

PDK trans. can disengage front axle ?
I came across an old article on Autoblog describing the early pdk's. The article suggests that you can disengaged the front drive axle on all PDK equipped c4 and c4s'; it does indicate whether the turbos can accomplish the trick. Can anyone who has applied the technique detail any problems or Joy with this feature. I found several press points on-line but no video, hence the request. Maybe the Porsche engineers changed the recent PDK to eliminate the feature ?

from AutoBlog : November 2008
The guys at Garage 419 found out from Porsche engineers that front-wheel drive can be disabled entirely by lifting up the parking brake a single notch. Once you lift up that brake, the four-wheel-drive Carerra 4 becomes a Carrera 2 and power slides and donuts are yours to discover.


from 911uk.com : Nov. 2008
By pulling up on the hand brake just one notch it's not the parking brake that comes on but what this Porsche actually does is disengage the front axle. Thereby turning the 997 (with a wink and nod) into a rear-wheel drive power slide maker.

 

Unfortunatley there is no "one notch" to engage.

 

Right, no brake lever to pull up one or any other "notch." The p-brake activation is electronic, push and pull type button.

Also, the power when on dry pavement, launching, is basically all at the rear anyways.... so disengaging the front drive wouldn't necessarily do anything for you, right? As for donuts or drifting, it is harder to set-up in all-wheel drive, but laws of physics regarding traction, mass and related apply just the same regardless of how many wheels are being powered.

 

Sorry that this is incorrect; even in the conditions you describe the awd prevents a full rear loading. That's why the c4s is quicker off the line; no wheel spinning.

so a small, yet nearly useless feature, of the 997.2 Carrera fours !

Though the fact that the 991 does not have a 'handle parking brake' doesn't mean this disengagement isn't possible. Someone at Porsche would know ?

And BTW without question there is a difference with the front tires simply rolling :-) donuts being the least important

 

Thanks for clarifying

I've taken my C4S out a number of times where I was able to spin the rears on a launch under Sport +, and with enough diving-in can perform some really fun donuts. In cases where I looked, I didn't see any of the bars on the load-display appearing in the front. But I also don't desire to spin my rears just for the sake of spinning, so can't honestly say that the tracks I left on the road weren't just a combination of tire, temp, and road type.... I do know that if I didn't set-up a donut "properly" I had a hard time NOT having the fronts bite and pull me out.

Of course, I am not a Porsche engineer or expert by any means, so maybe I am completely incorrect on all points....!