I drove one with an one without. Get it.

 

If I was getting a 991, the PDCC would be a "must have". It plays such a significant role in my CTT, but even though the 911 is much lower it still can benefit by such a great invention. From my understanding it does not allow the chassis to lean until the G's are greater then .75, then it lets it lean just a little.
When I am buying a sports car, its not time to be cheap and skip on performance options. I want it to be the best it can be for what it is used for 'sports'. If people want to skip on options to save money then skip on cosmetic ones like carbon fiber, leather, and contrast stitching. Not saying those aren't great too, but performance should far outweigh the looks for a sports car....me thinks.

 

 

Key questions:

- How much does PDCC improve objective performance, if at all? I know lack of lean will make the car feel like it's cornering better, but that doesn't necessarily mean grip is actually increased.

- If it does improve performance, how does it do it? Lateral forces are still a function of speed and curve radius, and CG shouldn't change significantly as a result of lean.

If PDCC is giving the appearance of substantially more cornering grip, but it's appearance only, that would take away some useful info regarding how close the car is to the limit.

 

Manifold - you know more about cars than to ask that. Think about negative camber in 991 wheels mixed with reduced body roll. Body roll always raises a car's CG.

And in your question above there was no reason to use the word "objective".

"How well does PDCC improve performance?" Performance is never subjective.

 

There are arguments that it will pay for itself in terms of lesser tire wear. If that is indeed true, then there is no harm paying for it. From a performance point of view it will remain unutilized in an urban setting but if you drive hard on a track you will likely benefit from it.

 

I don't follow how the negative camber part relates. Something to do with tire footprint on the road?

On the CG part, I can see it being raised a little, but not a lot, since one side is going down while the other goes up. And it's not clear to me how a large increase in cornering grip would result from controlling a small increase in CG height.

Also, I used the word 'objective' to make it clear that we're talking about measurable stuff like skidpad G, slalom speed, lap time, etc. Does anyone know how these numbers compare for the 991 with and without PDCC. That would settle it pretty definitively.

 

http://www.porsche.com/microsite/tec...1CarreraAllnew

Couple potential clues here: "optimised turn-in" and "stable load transfer characteristics". But I still want to understand it more clearly.

 

I would get it. For me, the whole point of going from a 997 to a 991 is to have the benefit of the new performance technologies -- PTV, PDCC, etc. For 2-3% of the total cost, that's not where I would look to save $$ -- purely personal objectives.

My dealer showed me a Porsche video from the 991 dealer education sessions at a track in California. It compared, in slow mo, a non PDCC and PDCC equipped 991 going around the same corner, same speed. The difference in body roll was very noticeable. For those of us who track and have seen track photos in the corners, this doesn't come as a surprise -- these cars body roll quite a bit in stock form.

 

Your understanding of cars and physics is much better than mine. All I can tell you is that on my test drives, I was taking turns at speeds that would have generated white hair in my 997 and would have had me off the road in my Mustang and it seemed like the 991 was not even pushing. Body lean was much less which meant I stayed in my seat and at the controls better. I drove on a clear day, but I bet that PDCC will be a real help in wet conditions or leaf covered roads as well. Seriously, it was one of the factors that made me move up to the S. I am sure it is a great car without it and in any set of normalish conditions, the car will still be an improvement over the 997.

 

I think a lot of us have driven the 991 without it and would say it didn't lean too much. Bit would it lean a lot less with the pdcc? You have to drive a pdcc car to decide.

 

If you can see the difference this easily, I can only imagine how different both cars feel. Long term reliability? What type of maintenance and how complicated is this system?

 

I'd ask 930man as he has a 991 with PDCC and has tracked his 4-5 times. Since it looks like he has owned/tried almost every variant since the 930, his answer would hold weight with me.

 

No doubt PDCC greatly reduces lean, and thereby improves confidence, but I'm still trying to figure out how much measurable performance difference it provides.

Jeez, I'm spending way too much time on this stuff! Should be working, but it's been a tough week, the weather's great right now, and I'm in a mood to goof off.

 

While there are certainly diminishing returns, the amount of lean and sway (and raising of CG) always negatively impacts the cornering performance of a car.

911's all have visually detectable negative camber for spirited cornering. Negative camber is zero'd out when 90* (perpendicular) outward lateral pressure and load is put at the axle - as opposed to the type of load body roll places "over the top" of the wheel. Ideally a car wants to be flat in hard corners. This works in conjunction with the amount of meat a tire puts on the road - and of course there is always the point of release when a tire can't grip anymore due to pure force.

I dont' think we are going to find measurable data yet on PDCC slalom - I'll look in Porsche technical bulletins in a bit when I get done with my work bs