I have to admit that when I first bought my 996TT about 4 years ago that I was pretty stoked about the stock AWD system. I see similar comments and feedback from folks even now as they buy these cars so figure it's still a pretty desirable feature that people give consideration to. But...

It seems to me that the 996TT based AWD system isn't a performance capable system at all. Meaning, it seems from what I've seen and read that it not only cannot transfer much torque at all to the front wheels but, worse yet, is pretty slow to react and really only works once you've already lost all traction at the rear.

With regard to the performance ambitions of this system, I've noticed nearly all of the big power guys have converted to RWD, and of course a lot of fair weather owners have done the same on even much more mildly built cars. Can anyone attest to any real performance advantages to the stock AWD system? Please note I'm not talking about it's ability to help get you out of a ditch, but real performance based criteria.

I already have some parts to convert to RWD (not an aftermarket rear differential yet), but would like to know about any big power guys who run AWD before I eventually take the plunge. That, and I actually want to help set the record straight for people who buy this platform thinking that it has a performance oriented AWD system, since it really seems to me that it's not the case at all. The 997TT certainly does in comparison, as we can see from recent videos, but that is of little help for us 996TT owners.

Thanks for your feedback all...seems like a dirty little secret that needs to be aired, at least from my own crazy POV.

 

You are not crazy. popcorn..

 

Tim,

I see this might not be a thread that many can contribute to, but I have a feeling your feedback and experience would be welcome.

At which point did you remove your own AWD system? What was your criteria for doing so? Observations gleaned from the before/after?

I know your car isn't exactly a common use case as it's pushing the boundaries of what is possible for this platform, but I suspect you got there over time and a lot of experimentation. So, I'd love to hear your feedback if you have the time...could help others as well. Thank you.

 

There will be something in the works from the HBK guys. Stay tuned....

 

This will be good!! I have also been curious about this!

 

My journey has been a long one. You need to ask yourself a few questions. What do I do with my car, road course? street/DE's? street/ strip? Just street?

How I see it. Why set my car up to blaze through tires when I cant even get close to turning the car that hard on the street? You can "detune" the alignment and save your tires and still not get to the breaking point on the street. With the aggressive alignment you trade off forward traction for lateral traction.

Where is the fun at? Ripping through the gears for me.. So once you set the suspension up and put tires for driving not style (no 19's with rubber bands) you will see you dont need the front drive till about 800-900 wheel hp. If you have boost by gear boost control or boost by speed you can stretch that number.

Front drive needed? Depends on the weather... The viscus coupling is not really all that.. I have had many 996's on the lift and have held back the front wheels with my hands with the car idling in gear. I would say it was useless in those cars..

After Etown and edelectra ripping on the unprepared track in his 997 got me thinking... but its only in very limited cases that it helps. Even still how much can the 997t drive take? It has the same ring and pinion as the 996 and if you search you will see at least one that broke the case on the dyno.

 

Personally, i think 600hp and awd is a great combination of performance and safety for the street.

 

After many high hp Eagle Talons (500-600hp), AWD on high hp cars has a serious advantage to me though the 911 AWD system and the talon vary somewhat. I just like not spinning the rears as bady as a pure RWD car. Even my 550i with 370hp spins badly in 1st and 2nd. The AWD just keeps thing under control for street driving. I'm an AWD guy though so that's really just opinion and no performance or track based fact. Unless the power would blow up the AWD system I'd never convert to RWD.

 

Guys like I have stated earlier.. Tires and alignment. Please with the 500hp wheel car blowing up the tires...Get rid of the bling 19's and rubber bands. ZO6's and mustangs do that and whip you in the quarter..

 

First off, thanks for the replies so far. Tim, you definitely had some things to say that lead me to want to ask more questions, but not just yet. I'm very keen on the notion of staying with 18" wheels on the Turbo so no problem there, but more curious about your alignment comments.

ttpopo, can you tell me how your AWD system behaves with 600hp, assuming that is what you're running? Do you notice it regularly transferring power to the front wheels and helping to maintain the balance of the car? Your statement is fairly general so I'd like to know if you have examples to back it up? That's what I'm looking for on this thread.

King James,

The other cars you mention are front engined so have less of a basis of comparison with a Porsche 911, which is a traction monster by nature of drivetrain layout. Obviously with a rear engined car, when the weight shifts under acceleration, you're really putting the weight down where it matters most for traction. With my nearly stock levels of power I've never had any traction problems whatsoever, nor have I ever detected the system shifting power up front (I'm sure it has, but nothing I've noticed). I've watched big power GT2 guys putting down a LOT more power than I have for years, and my research about the AWD system on the 996TT has led me to believe it's more of a hindrance than a help in terms of actual performance. That being said, I'm looking for concrete examples of people who are pushing a lot of power through it to see what they have learned and what they can share. Thanks for your reply.

 

My experience is based on aggressive street and track driving with a Pss9 based setup. I also spent a good deal of time discussing the issue with a cpl German tuners who routinely ADD an AWD system to their higher HP applications.

Sure, there's a touch of under steer that the system adds. You can eliminate most of it with bigger (235) front tires and proper suspension set up, but there's still inherent understeer at lower speeds due to the RR setup.

The point is that it's a safer setup with more performance than most drivers can handle. The system is almost 15 years old, and has been eclipsed by newer tech - yet, it still works well. It's most easily felt in late apex, power oversteer conditions. You'll feel the front end pull the rear end out of an *** end exchanging spin. With PSM off, it may not save you though.

Which brings up another thing - the system works best with PSM on. I'm not enough of a hotshoe that PSM slows me down though.

Personally, i think that if you really think PSM and AWD are slowing you down, go buy a GT2, put 600hp in that, go wreck it, then return back to this thread and tell me why AWD and PSM suck.

 

Thanks ttpopo, I appreciate the more detailed reply.

For the record, I'm not concerned with the understeer that the system adds. My primary concern while continuing to build the car is to add useful performance. As I'm sure you know, the 996TT falls under fire for being too heavy and soft relative to the world of GT3s and GT2s, and in my mind I'm pretty comfortable building a GT2 clone with PSM.

My car is a fair weather driver, no need to drive in rain/snow/ice unless I'm caught in a sudden downpour. As mentioned, I keep hearing of more and more people discarding the AWD system (this trend seems to be growing) and I'm mostly interested in hearing about the limitations of the system and what prompts folks to remove it. Their usage cases may or may not fit my own, but this is more of a research and education type of project for the moment.

Thanks again for taking time to answer.

 

By the way, I'm not talking about any 1/4" mile stuff. My experience is purely track based. I routinely feel the AWD traction advantage. It's primarily exhibited in higher speed transitions, switchbacks and corners - essentially allowing you to maintain more throttle angle in most situations, and allowing earlier application of (full) throttle at or before the apex.

It's particularly important for a turbo car, it essentially eliminates on-boost bad behavior, so you can use your power better - instead of rolling on slower. Different driving style for certain.

 

OH I can not leave this one alone, The AWD in my opinion is a good thing, not to invasive and with my suspension set up I can taylor under and over steer any way I want.

But I have a different view of the PSM. The PSM on a 996 sucks beyond words. For aggressive driving it chops power at the absolute wost time possible; and with my modified suspension it cycles in ABS at very in-opportune times too. unless I am just going on a slow milk run the very first ting I do is turn it off; when I drive really hard I would just as soon disconnect it 100%.

In short, unless I was making enough power that I worried about breaking the front drive-line I would rather have it. As per the ABS, I just do not get how some of you say that it is not a hinderance and that it actually does you more good then harm.

 

Thanks for your inputs Engine Guy.

I guess one of the core things I'm trying to answer (based on the experience of others) is what are the physical limitations of the stock system? At what power/torque rating have people truly overwhelmed the 996 based AWD system?