tmg57

PTV is simply a tool to help overcome the disadvantage of a 40/60 weight distribution. Another solution would be to move the engine into the back seat area. But then it wouldn't be 911, would it????

Mike in CA

Only the rear wheels of course, which is why in addition to the fact that keeping the car in a neutral attitude isn't PTV's intended function, (it's to enhance response to steering input and therefore agility) I don't think being able to brake just one rear wheel at a time would do much to correct instability. If anything, applying torque alternately by braking only individual rear wheels would tend to destabilize the car and make it want to turn which of course is the point of PTV when entering a corner in the first place. Also, PTV will apply only moderate brake pressure, so it doesn't have complete control over power application. It's not shutting down power to either wheel.

The Cayenne obviously isn't a sports car but it does handle really well. It goes where I point it, which makes it fun to drive, in part because of PTV. It doesn't feel artificial; it's just predictable and responsive. I suppose if it pushed more I'd have to compensate which would require more "involvement" but personally I don't find cars that understeer all that much fun to drive. PTV helps eliminate that, apparently in the GT3 as well, from all of the descriptions about how low speed understeer is all but gone.

As you said earlier, it's all about picking the place on the handling continuum that hits your sweet spot. Not everyone has a situation that allows for multiple sports cars so there are compromises and we all decide where to make them. There's not a right or wrong answer here; just saying that in my experience torque vectoring, if it's properly implemented, doesn't necessarily detract from the driving experience.

Manifold

My Cayenne GTS has PTV and I like the way it corners and handles on both road and track (yes, I've tracked it). But in a sports car, I like the challenge of getting the car through the corner, using techniques such as trailbraking, 'pitching' it into the corner, carrying yaw angle through the corner, lifting, and using power to get some oversteer (or neutralize understeer). PTV apparently makes these techniques largely unnecessary which, again, is good for lap times but maybe not so good for learning to drive and having fun doing it.

Mike in CA

Manifold, you keep using the word "apparently" however there is nothing apparent about it. Torque vectoring simply doesn't work the way you think it does, and has no affect on trailbraking or the ability to do any of the other things you mention.

If you don't believe that based on a description of how it works, surely you've seen the videos with CH, Suttcliffe, and others pitching GT3's with PTV, into turns, hanging out the tail, and making adjustments with the throttle. You don't need to worry that torque vectoring will ruin the fun.

Manifold

I guess it's a matter of how active PTV is. I hope you're right that the effect isn't too much -- good point regarding those videos.

frayed

Mike, though I've not driven a PTV car, I understand that the computer modulates L/R rear wheel tq from 0 to 100%. Fully open to fully locked and everywhere inbetween. And, it can brake wheels as necessary to maintain your intended line based on throttle position, steering position, speed, yaw sensors etc etc.

In essence, it takes a mechanical LSD and adds a brain to it and can now accomplish things in terms of balance that a mechanical unit cannot, since all mechanical units have tradeoffs. I take CH, Suttlcliffe's etc antics with a grain of salt. I doubt very much these fellas were getting her all loose b/c they had to in order to turn a fast lap. It was for show.

I still remember Clarkson's yeeeeehaaaaw when he drove the 430 with the ediff stating how it made him look like a superhero.

SamFromTX

In my opinion/experience, PTV is overblown when it comes to track driving. I have tracked my current PTV car 29 days since I took delivery January. While PTV may very well help you steer and in doing so, it allows you to go a bit faster, at which speed its benefit becomes diluted and all the functions you describe (trail braking, pitching the car, etc) are 100% maintained albeit at a slightly higher speed, compared to no PTV. The involvement and enjoyment is definitely there. That is what I experienced, of course. Others may have a different experience/opinion.

Mike in CA

frayed, I think you're referring to two different things; e-diff and PTV. The e-diff is fully variable from open to locked and does shift torque from wheel to wheel. While PTV might sometimes be functioning at the same time it involves only the brakes, and only when there is input to the steering wheel. Porsche describes PTV working at corner entry and e-diff working mainly to put the power down at corner exit. As we've discussed PTV may also work if there are steering adjustments in mid-corner but not independent of driver input, like the way PSM works.

I don't doubt that CH et al were doing what they were doing for show. The point is that PTV wasn't preventing them from hanging out the tail or balancing the car with the throttle which I think was Manifold's concern.

SamFromTexas has it exactly right. PTV is a minor aid, not a cure-all or savior, and from what I understand about it, it doesn't keep you from doing what you want to do with the car.

Manifold

Mulling this over further, there's still the question of how much need there is for those techniques when you have PTV, even if PTV doesn't prevent using them. And related to that, the calibration of PTV may be different in the 991 GT3 as compared to other Porsches. Walter Rohrl's comments continue to reinforce my concern that this car may be helping the driver too much, at least too much for my taste.

Mike in CA

PTV doesn't actively distribute power. It's simple physics. One wheel is slowed slightly by moderate braking. The other wheel is now turning slightly faster so it causes the car to want to rotate. It's effective at turn in but not elsewhere and gives the chassis a nudge, not a major adjustment. All the other things you want to do with the car won't become unnecessary.

We can talk about this till we're blue in the face. When cars start to get into the hands of owners we'll find out what's what. I get that some don't want to take the chance but I honestly think the risk of disappointment is very low. Just my $.02......

Manifold

Any time PTV taps the brake of the inside rear wheel, that will help the car rotate, and in principle PTV can do that as often as it wants when entering and going through a corner. So I see nothing indicating that PTV couldn't be so effective that the need for those other techniques becomes largely unnecessary. And why wouldn't Porsche make PTV as effective as it can be?

Probably also worth noting that I heard last year from a 991S driver that his rear brake pads were getting used up much faster than his front pads on track, apparently because PTV was pretty busy back there. In cars without PTV, the rear pads generally last at least twice as long as the front pads.

frayed

Mike, I think you have it wrong.

http://press.porsche.com/vehicles/2014/2014_GT3_USA.pdf

"The rear axle of the new 911 GT3 is equipped with Porsche Torque Vectoring Plus (PTV Plus)
as standard. The system, which was adapted specifically for the 911 GT3, consists of an
electronically controlled, fully variable locking rear differential and selective braking inter -
ven tions at the rear wheels. In combination, these features provide high traction on changing
road surfaces, an improvement of lateral dynamics, more precise cornering, and increased
driving stability"

It's essentially a smart mechanical diff. Doesn't take the fun out of trail braking, inducing some rotation midcorner with some lift, or pitching the car around. Rather, I bet money that it will *remove* the need for some portion of these inputs given the 3's ability to hold a line.

Whether it's PTV a combination of PTV + RWS, or PTV + RWS + PASM + enhanced track and wheelbase. . . I guess it doesn't really matter. You can't turn these items off so you are stuck with a more *perfect* car, like it or not! LOL.

I'm not terribly concerned as I see the issue as the natural extension of the 997 GT3.

Manifold

I had hoped the 991 GT3 would be similar to the 997 GT3, except that it would make use of the 991's longer wheelbase, wider front track, etc. - the attributes which make a base 991 handle and perform better than a base 997. Instead, we're getting mandatory PDK, mandatory PTV Plus, and other mandatory features which make the car faster and easier to drive, but also less involving and less challenging in ways that develop and reward driver skill - basically going in the direction of the GT-R, perhaps largely in order to compete with it.

frayed

I believe it was Stout? who said that while he has a lot of respect for the GT-R, the GT3 is not anything like it despite all the electronics.

Manifold, I wouldn't get yourself too worked up about anything in the car other than PDK based on the reviews we've gotten so far from CH Sutcliffe and Stout.

PDK aside, it's a 10/10.

So let's focus on the MT/PDK debate, shall we?

j/k

Manifold

I don't expect the GT3 to be much like the GT-R overall, and I'd definitely pick the GT3 between the two, but I think the GT3 has definitely moved in the GT-R's direction, and the question now is whether it's too much. I started this thread because I haven't seen PTV discussed much, and I'm fearing that its effect may be more than people realize.