911SLOW

Guys, knock it off, please. The discussion is interesting enough without personal attacks and name callings.

Nick, let it go please. It's none of your business.

Dave, you are a sponsor here! Please act accordingly in all the forums.

Last warning and thanks,

The Greek

John,

No problem, that's my fault.


PSM I believe affects front brakes on a slide if I remember correctly. Not 100% sure though....

Veloce Raptor

OK, John, no prob.

911SLOW

Thanks guys!


Back to deviated stitching now.

Veloce Raptor

Anyway, getting back to the PTV+ thing, if in fact the new GT3 has it, I wonder why? It seemed to me that the 997 GT3 rotated extremely well and was very easy to point into a corner.

It's almost as if it's tech creep solely for the sake of tech...sort of like the faux center locks.

mdrums

With the GT3 if Porsche is putting all these P something something stability gizzmo's on the car I sure hope there is a true OFF button for those that don't want to use them.

However fine put the gizmo's on the car but please give a 5 lug bolt options...PLEASE!

Mike in CA

Hard to know what's in the mind of Porsche, but FWIW PTV+ is standard on the 991 S. Maybe they felt the 991 GT3 needed it to keep the gap between the two 991 models as wide as possible. Just guessing.....

Bob Rouleau

Guys, PTV is clearly misunderstood by some in this thread. It is NOT a substitute for trail braking - which is done at corner entry and you are braking the car using the weight transfer to the front to provide better turn in and rotation of the car into the apex.

PTV is Porsche's version of what Ferrari calls E-Diff. By applying the brake lightly to the inside rear wheel WHILE UNDER POWER more torque is sent to the outside wheel which helps keep the car on line. In practice it feels like the hand-of-God is on your outside rear fender keeping the car from stepping out powering out of the corner. Does it work? Well they banned it in F1 so I think we can say that yes, it does.

Those who live in the snow belt know that lightly applying the handbrake (if it is on the rear wheels of a rear drive car) can help get out of snow when a car without LSD spins one rear wheel which without LSD gets all the torque whereas the wheel with some traction gets none. This may help visualize what PTV does.

Another way to look at it would be to imagine a locked differential, i.e. both wheels always turn at the same speed - talk about understeer! A modern LSD allows a certain percentage of lock-up under acceleration - around 20 percent or so on a 911 so equipped. Any amount of power to the inside rear wheel while in a corner will cause some steering effects. PTV prevents that. By applying a bit of drag to the inside rear wheel more power goes to the outside wheel which is beneficial.

I hope this lends some clarity to the discussion and like John asked, let's all keep it civil please.

Oh, as to the comment about premature brake wear, yes I think PTV might do that. On the other hand PSM is certainly a major reason for premature pad and rotor wear on the rear of a Porsche. Not all Porsches have PTV but all the modern cars have PSM.

Best,

Veloce Raptor

So perhaps the 991 S has a lot of factory-standard understeer like the 997 S did? I don't know. I have not driven a 991 S yet. But the 991 S and the GT3 are vastly different animals, and I would hope that the lattter would not have the former's (likely) understeer issues.

Mike in CA

Another voice of reason. Thank you.....

Marine Blue

Does the Audi R8 have something similar to PTV and is that the reason for the additional set of small calipers in the rear?

Mike in CA

I have not experienced a lot of factory standard understeer on my 997.2 S but I have the lower, siffer, sport suspension with as much front camber dialed in as I can get with factory parts, so that may explain it. PTV isn't standard on the base 991 and every review I've seen on it has complimented it's neutral handling. Nor have I seen anything but positive handling reviews on the 991S which is standard with PTV+. I obviously don't know anything yet about the 991 GT3. I'd suggest it's not a matter of compensating for too much understeer, but rather something that Porsche feels makes really good steering response even better.

Veloce Raptor

OK...here's what they say:

"PTV in conjunction with the manual gearbox, or PTV Plus with Porsche Doppelkupplung (PDK)...actively enhance vehicle dynamics and stability. Operating in conjunction with ... electronic (PTV Plus) rear differential lock, they work by braking the rear wheels as the situation demands.

As a function of steering angle and steering speed, accelerator pedal position, yaw rate and vehicle speed, PTV and PTV Plus are able to improve steering response and steering precision by specific braking of the right or left rear wheel.

To be more precise, this means that when the car is driven assertively into a corner, moderate brake pressure is applied to the inside rear wheel. Consequently, a greater amount of drive force is distributed to the outside rear wheel, inducing an additional rotational pulse (yaw movement) around the vehicle’s vertical axis. This results in a direct and sporty steering action as the car enters the corner."

When I read "enters the corner" that says to me "at the end of the braking cycle", IE, trail braking. You typically don't drive "assertively" into a corner w/o braking unless you are going 5 MPH.

So I am using Porsche's own words here, Bob & Mike. You claim to know otherwise--how are we to interpret Porsche's own words here in your views?

Carrera GT

Secondary rear calipers are the parking brake.

The 991S rear calipers don't have any trouble dishing out PTV/PSM/PSY on the track at a decent pace. Just so long as there's a switch for PTV along with SC and TC, all will be well.

Bob Rouleau

Dave, dunno about Porsche's definition of being driven assertively into the corner...on the other hand it does say transfers torque to the outside wheel. This is not like PSM which tries to straighten a car out - I bet you've felt it when trail braking a PSM car - I have, damn near took me off the track Moving torque to the outside wheel improves cornering, in my 430 with e-diff the feeling in high speed corners was very noticeable especially on sticky tires. I haven't driven a 991S on slicks yet, but on street tires the thing corners very well with LESS UNDERSTEER than a GT3. Everyone who has tried the 991 on a track has noticed how pointy the car is compared to the 997. Not sure how they did it, wider tires and track in front help for sure, there may be other things they've done. The next GT3 should be amazing, and like others I hope there is an "off" button for the nannies. On my RS PSM isn't so bad, but traction control is way too sensitive. PSM does get upset trail braking on slicks, street tires not so much.. Have you had the same experience?