What is the 7-speed manual gearbox? - Page 2 - Rennlist - Porsche Discussion Forums

Notices
991 GT3 GT3RS and 911R
Sponsored by:

What is the 7-speed manual gearbox?

 
Old 03-21-2013, 02:24 AM
  #16  
GTgears
Super User
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,058
Default

http://www.porsche.com/microsite/tec...lectedVariant=

Right in the first paragraph they say it is brakes. They throw a lot more techno gibberish in and try to make it sound fancy and complicated but they plainly say that it is brakes. They pay people a lot of money to confuse the consumer.
GTgears is offline  
Old 03-21-2013, 04:08 AM
  #17  
Mike in CA
Addict
Rennlist Member
 
Mike in CA's Avatar
 
Join Date: Jun 2001
Location: North Bay Area, CA
Posts: 11,865
Default

Originally Posted by GTgears View Post
http://www.porsche.com/microsite/tec...lectedVariant=

Right in the first paragraph they say it is brakes. They throw a lot more techno gibberish in and try to make it sound fancy and complicated but they plainly say that it is brakes. They pay people a lot of money to confuse the consumer.
They also say it works in conjunction with a mechanical LSD (PTV) or electronic LSD (PTV+). As I posted earlier PTV+ is also available on the Cayenne and basically works the same as the system in the 991 except for the ability to manually lock both the center and rear differentials in the Cayenne with a switch. (Please don't tell me the center diff in my Cayenne is locked by the brakes too. )

There are two features with PTV+; the braking function which acts on the inside rear wheel to help rotate the vehicle and an electronically controlled diff. The following excerpts are from my Cayenne S owner's manual:

PTV Plus
Porsche Torque Vectoring
– Lateral dynamic braking for sportier and more agile cornering
– Electronically controlled rear differential lock


Information Rear differential lock
When the rear differential lock is fully engaged,
there is no longer any speed difference between
the two rear wheels. This makes it easier for the
vehicle to keep moving if, for example, one drive
wheel on the rear axle loses traction on an icy road
or soft surface.


The electronically controlled rear differential lock
continuously checks the driving situation of the
vehicle and distributes the drive torque to the rear
axle as required. This has the following
advantages:
– Improved traction
– Reduced load change responses when
cornering at speed
– Improved driving stability at higher speeds
– Off-road traction is also significantly improved
due to the possibility of locking the rear
axle fully.


The above text isn't techno-gibberish; it's plain English. Either that or some of the most deliberately misleading statements I've ever read. I'd be willing to make a small wager as to which it is.

Last edited by Mike in CA; 03-21-2013 at 05:02 AM.
Mike in CA is offline  
Old 03-21-2013, 09:57 AM
  #18  
TRAKCAR
Addict
Rennlist Member
 
TRAKCAR's Avatar
 
Join Date: Jan 2008
Location: S. Florida
Posts: 26,682
Default

Originally Posted by Mike in CA View Post
The above text isn't techno-gibberish; it's marketing gibberish that works on a Cayenne but is bullsh!t on what's supposed to be the purest driving track machine you can buy off the showroom floor and drive straight to the track. Either that or some of the most deliberately misleading statements I've ever read. I'd be willing to make a small wager as to which it is.
Fixed it.
TRAKCAR is online now  
Old 03-21-2013, 12:30 PM
  #19  
savyboy
Addict
Rennlist Member
 
savyboy's Avatar
 
Join Date: Nov 2008
Location: Reno NV
Posts: 3,362
Default

Originally Posted by TRAKCAR View Post
Fixed it.
You are killing me!

Until Matt brought this up, I actually gave Porsche the benefit of the doubt that they had fixed the previous generation crap LSD's in the 991 GT3 (they did fix the PCCB by correcting the sizing/caliper rigidity). Ha!

So, in all fairness, here is the specific marketing-speak in regards to the GT3 PTV/LSD, not the Cayenne system (which has nothing to do with a GT3!):

http://www.porsche.com/microsite/tec...t=PMT911GT3All

"Porsche Torque Vectoring Plus is fitted as standard and has been specially adapted to the new 911 GT3. It operates in conjunction with an electronically regulated and fully variable rear differential lock (what, exactly does this mean? Is it a new LSD ? Or is it a gibberish way to say they are using the brakes to make the diff work? Another example of BS in lieu of honesty). Numerous driving parameter inputs are the basis for the system’s active control outputs. The results are perceptible, particularly at the limits of dynamic performance: greater traction, increased lateral dynamics and a significant improvement in driving stability under the effects of load changes in corners and when the car changes lane.

On surfaces with less grip, such as in the wet, the system strategically brakes the right or left rear wheel. This means that, whenever the car enters a corner, brake pressure is applied to the inside rear wheel. Consequently, a greater amount of drive force is distributed to the outside rear wheel. This improves steering behaviour and increases agility."

I see nothing there about an LSD that is more durable than the previous GT3 diff or more motorsport oriented. I do see the brakes being used to make the diff work as opposed to ramp angle, preload or clutch pack composition.

I have nothing against so-called PTV. I do have something against a OE diff that is not up to track work (as the .1 and .2 diffs are not). If as Matt thinks, it is the same marketing BS over reality, it is the final nail in the GT3 coffin for me. I'll be damned if I will spend money again on the same GD deficiencies that the past previous generations have. Porsche can speak to this and clear the air any time they like...of if some yellow-bellied journalist finds the testicular fortitude to ask the direct question of a Porsche rep...
savyboy is offline  
Old 03-21-2013, 12:43 PM
  #20  
TRAKCAR
Addict
Rennlist Member
 
TRAKCAR's Avatar
 
Join Date: Jan 2008
Location: S. Florida
Posts: 26,682
Default

Pete, the brakes are actually pretty decent of the 997GT3's and the new PFC brakes are the most delicious part of the new 991GT3, but I suppose it may need extra brakes if they are used for cornering.

Hmm, Who was first to start running PFC stuff again?

LSD; Matt?

Last edited by TRAKCAR; 03-21-2013 at 01:09 PM.
TRAKCAR is online now  
Old 03-21-2013, 01:07 PM
  #21  
GTgears
Super User
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,058
Default

Like Pete has said, the fact that they use the same name for something on the Cayenne as they are using on the Carreras and GT3 doesn't mean that it is the same thing. A center diff or rear diff pumkin on an AWD SUV has nothing to do with the differential inside the transaxle. And what Pete just posted is very similar to the blurb I linked last night that was specific to the Carrera.

This is what I can tell you for a fact. When we opened up the 7MT gearbox to remove the differential for measurements, it looked like any other mechanical LSD. I will admit that we didn't realize we were going to find an LSD in there when we cracked it open. But what we have assumed is that instead of an M220 optional LSD anymore now they are using the PTV for indicating the presence of a mechanical LSD. That's the mechanical part of the description, and it is the same anemic internals as found on the PDKs, which makes sense since the 7MT is PDK based.

The electronic part,the PTV+, as has been mentioned, is the brakes. There is no allowance on the body of the differential for varying the pressure or locking factor.

Porsche has used adjustable differentials in the past. Both the center diff and the rear diff (inside the transaxle) on the 964 C4 were adjustable. Look at this skematic from PET:


See that big wing on the top end? That is there because there is a piston mounted to the outside of the gearbox case that exerts pressure on it when there is wheelspin. The center differential has something very similar. It was technology that came out of the 959 project and was applied to the street cars, in large part to help defray the massive losses they were taking on the 959. They had to try to recover some of their investment somewhere.

But moving forward to the 993 C4 they went back to 100% mechanical. The electronic/hydraulic stuff was too problematic from a long term reliability and cost standpoint. As they went forward, they did eventually introduce the ABD and now they have refined it and renamed it PTV. My understanding of how the system works in the Carreras is that it is a very low locking factor LSD along with braking intervention. And my direct experience with the 991 7MT gearbox suggests that nothing has changed for the newest generation of cars.

Which leads me back to my question about what the GT3 really is. Given the close similarity of the marketing text, my hip shot inclination is that the GT3 is no different except they have now added yet another variable to the equation, rear wheel steering.
GTgears is offline  
Old 03-21-2013, 01:37 PM
  #22  
TRAKCAR
Addict
Rennlist Member
 
TRAKCAR's Avatar
 
Join Date: Jan 2008
Location: S. Florida
Posts: 26,682
Default

Thanks Matt!

The rev matching can be cool if you can turn it off and the display on the dash is a bit gimmicky but I suppose it helps drivers with wondering minds..

This does look like more fun to me, I wonder why they put it in the C2S:
TRAKCAR is online now  
Old 03-21-2013, 01:39 PM
  #23  
Carrera GT
Wordsmith
Rennlist Member
Thread Starter
 
Carrera GT's Avatar
 
Join Date: Feb 2003
Posts: 8,612
Default

Originally Posted by savyboy View Post
You are killing me!

Until Matt brought this up, I actually gave Porsche the benefit of the doubt that they had fixed the previous generation crap LSD's in the 991 GT3 (they did fix the PCCB by correcting the sizing/caliper rigidity). Ha!

So, in all fairness, here is the specific marketing-speak in regards to the GT3 PTV/LSD, not the Cayenne system (which has nothing to do with a GT3!):

http://www.porsche.com/microsite/tec...t=PMT911GT3All

"Porsche Torque Vectoring Plus is fitted as standard and has been specially adapted to the new 911 GT3. It operates in conjunction with an electronically regulated and fully variable rear differential lock (what, exactly does this mean? Is it a new LSD ? Or is it a gibberish way to say they are using the brakes to make the diff work? Another example of BS in lieu of honesty). Numerous driving parameter inputs are the basis for the systemĺs active control outputs. The results are perceptible, particularly at the limits of dynamic performance: greater traction, increased lateral dynamics and a significant improvement in driving stability under the effects of load changes in corners and when the car changes lane.

On surfaces with less grip, such as in the wet, the system strategically brakes the right or left rear wheel. This means that, whenever the car enters a corner, brake pressure is applied to the inside rear wheel. Consequently, a greater amount of drive force is distributed to the outside rear wheel. This improves steering behaviour and increases agility."

I see nothing there about an LSD that is more durable than the previous GT3 diff or more motorsport oriented. I do see the brakes being used to make the diff work as opposed to ramp angle, preload or clutch pack composition.

I have nothing against so-called PTV. I do have something against a OE diff that is not up to track work (as the .1 and .2 diffs are not). If as Matt thinks, it is the same marketing BS over reality, it is the final nail in the GT3 coffin for me. I'll be damned if I will spend money again on the same GD deficiencies that the past previous generations have. Porsche can speak to this and clear the air any time they like...of if some yellow-bellied journalist finds the testicular fortitude to ask the direct question of a Porsche rep...
I don't see anything too ambiguous about "electronically regulated and fully variable rear differential lock." There's no room in that description for brake differential.

I'm not sure if it's PDCC or PSM or PTV (all of which infest my 991S) but the car has some terrible manners when driven moderately through sweeping turns with undulating road surfaces. It's pretty much only when driven lightly or driven aggressively (well past a balanced throttle) that the car will stop intervening.
Carrera GT is offline  
Old 03-21-2013, 02:16 PM
  #24  
savyboy
Addict
Rennlist Member
 
savyboy's Avatar
 
Join Date: Nov 2008
Location: Reno NV
Posts: 3,362
Default

Originally Posted by Carrera GT View Post
I don't see anything too ambiguous about "electronically regulated and fully variable rear differential lock." There's no room in that description for brake differential.
Yet...based upon Matt's post above, The Great Porsche Marketing Machine strikes again, and it is 100% brake differential?

The deeper the hole goes, the more crap is found. Like digging under a centuries old outhouse. Oh my...have they no shame at all?

I guess when you have paddles that help you do a donut, nothing else matters

Follow-up edit- they found shame and appear to have fixed the previous generations door-stop diff.

Last edited by savyboy; 03-22-2013 at 07:33 PM. Reason: Shame found!
savyboy is offline  
Old 03-21-2013, 02:44 PM
  #25  
Carrera GT
Wordsmith
Rennlist Member
Thread Starter
 
Carrera GT's Avatar
 
Join Date: Feb 2003
Posts: 8,612
Default

Originally Posted by savyboy View Post
Yet...based upon Matt's post above, The Great Porsche Marketing Machine strikes again, and it is 100% brake differential?

The deeper the hole goes, the more crap is found. Like digging under a centuries old outhouse. Oh my...have they no shame at all?

I guess when you have paddles that help you do a donut, nothing else matters
I think this thread has degenerated into argumentation deciphering marketing copy. Porsche wrote there's an electrically variable diff in the GT3. There's also rear braking in the GT3 as part of PTV+. It's not a 100% wheel brake, there's nothing ambiguous in what they've written.

I have my reservations about the 991, Carrera and GT3, but it goes to far to characterize PTV as some shameless skulduggery by Porsche.

The question remains as to whether it's durable, which is moot until the pudding is eaten.
Carrera GT is offline  
Old 03-21-2013, 03:00 PM
  #26  
Nizer
Addict
Rennlist Member
 
Nizer's Avatar
 
Join Date: Feb 2006
Location: Beta Testing
Posts: 10,716
Default

I'm just trying to figure out where you'd fit a mechanical diff in the PDK case?
Attached Images  
Nizer is offline  
Old 03-21-2013, 03:33 PM
  #27  
Mike in CA
Addict
Rennlist Member
 
Mike in CA's Avatar
 
Join Date: Jun 2001
Location: North Bay Area, CA
Posts: 11,865
Default

Originally Posted by TRAKCAR View Post
Fixed it.
You can edit!!

Originally Posted by GTgears View Post
Like Pete has said, the fact that they use the same name for something on the Cayenne as they are using on the Carreras and GT3 doesn't mean that it is the same thing. A center diff or rear diff pumkin on an AWD SUV has nothing to do with the differential inside the transaxle. And what Pete just posted is very similar to the blurb I linked last night that was specific to the Carrera.

This is what I can tell you for a fact. When we opened up the 7MT gearbox to remove the differential for measurements, it looked like any other mechanical LSD. I will admit that we didn't realize we were going to find an LSD in there when we cracked it open. But what we have assumed is that instead of an M220 optional LSD anymore now they are using the PTV for indicating the presence of a mechanical LSD. That's the mechanical part of the description, and it is the same anemic internals as found on the PDKs, which makes sense since the 7MT is PDK based.

The electronic part,the PTV+, as has been mentioned, is the brakes. There is no allowance on the body of the differential for varying the pressure or locking factor.

Porsche has used adjustable differentials in the past. Both the center diff and the rear diff (inside the transaxle) on the 964 C4 were adjustable. Look at this skematic from PET:

See that big wing on the top end? That is there because there is a piston mounted to the outside of the gearbox case that exerts pressure on it when there is wheelspin. The center differential has something very similar. It was technology that came out of the 959 project and was applied to the street cars, in large part to help defray the massive losses they were taking on the 959. They had to try to recover some of their investment somewhere.

But moving forward to the 993 C4 they went back to 100% mechanical. The electronic/hydraulic stuff was too problematic from a long term reliability and cost standpoint. As they went forward, they did eventually introduce the ABD and now they have refined it and renamed it PTV. My understanding of how the system works in the Carreras is that it is a very low locking factor LSD along with braking intervention. And my direct experience with the 991 7MT gearbox suggests that nothing has changed for the newest generation of cars.

Which leads me back to my question about what the GT3 really is. Given the close similarity of the marketing text, my hip shot inclination is that the GT3 is no different except they have now added yet another variable to the equation, rear wheel steering.
Great post. I appreciate the time you spent putting that explanation together. Just a couple of things.

The differences between the drive layouts in the Cayenne and Carrera/GT3 are obvious. It seems strange to me, though, that Porsche would use the exact same nomenclature (PTV+) for two series of cars, describe the same components, and describe the operating features pretty much identically, and yet in one case there is an electronic locking diff and in the other there isn't. But you guys say it's marketing speak. OK. Also, the schematic of the 964 is very interesting. I'm just not sure how much can be extrapolated from a 25 year old AWD design to the new Carrera's and their gearboxes.

You mention that when you cracked open a 7sp PDK derived manual you were surprised to find a mechanical LSD that looked like any other. That's interesting, because the 7sp MT became available a few months into the 991 model run. PTV has been available since the 991 was introduced. If Porsche were now using the brake function of PTV in place of a real mechanical (or electronic) locking diff, as you assume, why did you find a real one in the case you opened? This means Porsche began by producing Carreras with PTV, and introduced the 7sp MT Carreras with real mechanical LSD's and PTV. Then going forward they are going to eliminate the actual mechanical LSD, like you found, and instead use PTV or PTV+ with no real locking differential at all. That seems very unlikely to me.

To be clear (and I'm just going by the Porsche techno-gibberish here), there are two seperate functions involved with PTV/PTV+. Both systems use brake intervention on the inside rear wheel to cause more power (torque vectoring) to be channeled to the outside wheel which helps rotate the car as you enter a turn. That's the PTV part. With a manual gearbox, this is combined with a mechanical LSD, just like the one you found when you cracked that 7sp MT case. The "+" part is the electronically variable LSD, which takes the place of the mechanical one, and is available only with PDK.

I have no argument with what torque vectoring is or how it works. Clearly it uses the brakes. How effective it is on the GT3 remains to be seen, although from my personal experience with PTV in the Cayenne, it works as advertised. The discussion has arisen over the other functionalities including the "+"; whether, as Porsche claims, there actually is a mechanical LSD for the MT (well, we know there is, you found one) or a continuously variable electronic LSD (the "+") that comes with PDK.

Even you have said you are making some assumptions and shooting from the hip. For now, I guess I'll go with what appears to me to be a pretty plain English description from Porsche of what their product is and what it includes. When you've had a chance to open a PTV+ equipped 991 PDK gearbox, let us know what you find. If I'm wrong I'll gladly admit it.

Last edited by Mike in CA; 03-21-2013 at 03:50 PM.
Mike in CA is offline  
Old 03-21-2013, 03:34 PM
  #28  
GTgears
Super User
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,058
Default

It is skinny. Here's a comparison of the GT3 LSD next to the 991 version. Internally the GT3 is +/-95mm. The 991 is a good 15mm smaller. At first we weren't even sure we would be able to make it fit and still perform the way we wanted it to. But BGB just got back from 2 days and nearly 500 track miles at Barber in both the sun and the rain. LSD works like a dream and the car is really fast right out of the box. It was turning 2:00 laps at Daytona before adding our LSD and just a tire change. We're interested to get it back there soon for a revised lap time.
GTgears is offline  
Old 03-21-2013, 03:40 PM
  #29  
GTgears
Super User
 
GTgears's Avatar
 
Join Date: Oct 2009
Location: Loveland, CO
Posts: 5,058
Default

Originally Posted by Mike in CA View Post
You can edit!!



Great post. I appreciate the time you spent putting that explanation together. Just a couple of things.

The differences between the drive layouts in the Cayenne and Carrera/GT3 are obvious. It seems strange to me, though, that Porsche would use the exact same nomenclature (PTV+) for two series of cars, describe the same components, and describe the operating features pretty much identically, and yet in one case there is an electronic locking diff and in the other there isn't. But you guys say it's marketing speak. OK. Also, the schematic of the 964 is very interesting. I'm just not sure how much can be extrapolated from a 25 year old AWD design to the new Carrera's and their gearboxes.

You mention that when you cracked open a 7sp PDK derived manual you were surprised to find a mechanical LSD that looked like any other. That's interesting, because the 7sp MT became available a few months into the 991 model run and the 991S has come standard since it's introduction with PTV+. If Porsche were now using the brake function of PTV in place of a real mechanical (or electronic) locking diff, why did you find a real one in the case you opened? This means Porsche began by producing Carreras with PTV+, then introduced the 7sp MT Carreras with real mechanical LSD's and PTV. Then, based on your assumption, going forward they are going to eliminate the actual mechanical LSD, like you found, and instead use PTV or PTV+ with no real locking differential at all. That seems very unlikely to me.

To be clear (and I'm just going by the Porsche techno-gibberish here), there are two seperate functions involved with PTV/PTV+. Both systems use brake intervention on the inside rear wheel to cause more power (torque vectoring) to be channeled to the outside wheel which helps rotate the car as you enter a turn. That's the PTV part. With a manual gearbox, this is combined with a mechanical LSD, just like the one you found when you cracked that 7sp MT case. The "+" part is the electronically variable LSD, which takes the place of the mechanical one, and is available only with PDK.

I have no argument with what torque vectoring is or how it works. Clearly it uses the brakes. How effective it is on the GT3 remains to be seen, although from my personal experience with PTV in the Cayenne and what I've read about it in the Carrera, it works as advertised. The discussion has arisen over the other functionalities including the "+"; whether there actually is a mechanical LSD for the MT (well, we know there is, you found one) or a continuously variable electronic LSD (the "+") that comes with PDK.

Even you have said you are making some assumptions and shooting from the hip. For now, I guess I'll go with what appears to me to be a pretty plain English description from Porsche of what their product is and what it includes. When you've had a chance to open a PTV+ equipped 991 PDK gearbox, let us know what you find. If I'm wrong I'll gladly admit it.
Mike,

I think you are making an argument that is counter to what I am saying. I have never said that cars with PTV or PTV+ weren't going to see mechanical LSDs. What I am saying is that they don't have any sort of electronic LSD actuation. They don't have active diffs, at least in the Carreras. The center diff in your Cayenne and its on the fly locking is EXACTLY the sort of thing I am saying is absent from the Carrera's PTV systems. The LSD in the Carrera is 100% mechanical with none of the dynamic behaviour that either your Cayenne, the 964 C4 or the Koenigsegg have. You seem to be arguing that there is a mechanical LSD in the car when that is something that I never disputed. The kind of mechanical LSD is what I am questioning.
GTgears is offline  
Old 03-21-2013, 04:21 PM
  #30  
Mike in CA
Addict
Rennlist Member
 
Mike in CA's Avatar
 
Join Date: Jun 2001
Location: North Bay Area, CA
Posts: 11,865
Default

Originally Posted by GTgears View Post
Mike,

I think you are making an argument that is counter to what I am saying. I have never said that cars with PTV or PTV+ weren't going to see mechanical LSDs. What I am saying is that they don't have any sort of electronic LSD actuation. They don't have active diffs, at least in the Carreras. The center diff in your Cayenne and its on the fly locking is EXACTLY the sort of thing I am saying is absent from the Carrera's PTV systems. The LSD in the Carrera is 100% mechanical with none of the dynamic behaviour that either your Cayenne, the 964 C4 or the Koenigsegg have. You seem to be arguing that there is a mechanical LSD in the car when that is something that I never disputed. The kind of mechanical LSD is what I am questioning.
Matt,

Sorry, I don't mean to be argumentative. I was confused by your statement:

But what we have assumed is that instead of an M220 optional LSD anymore now they are using the PTV for indicating the presence of a mechanical LSD. That's the mechanical part of the description, and it is the same anemic internals as found on the PDKs, which makes sense since the 7MT is PDK based.

I interpeted that to mean that PTV (brake actuated torque vectoring) was going to take the place of the M220 LSD, Apparently you meant that there a renaming of the mechanical LSD to PTV. Ok, well we're making progress in terms of understanding each other. BTW, in reference to your comment above about the center diff on the Cayenne, the diff on the rear axle (where PTV is in play) is also lockable on the fly.

Anyway, what I'm saying is that Porsche in their literature claims a PTV function and a mechanical LSD for their MT Carreras. This, we now agree, is true. They also claim that on their 991 PDK equipped Carreras, and now the 991 GT3, there is a PTV function and a "+", an electronically controlled locking diff. My question is, what evidence do you have that this is not true?

To date, the 991 PDK gearbox is the only one in the Carrera line with PTV+ and electronic locking. Have you opened one of these and found no sign of a mechanism for control of variable electronic locking? It seems strange that Porsche would have a mechanical LSD to augment PTV in their MT cars, and nothing in their PDK cars or the GT3, but if there's proof of that then so be it.
Mike in CA is offline  

Thread Tools
Search this Thread
Quick Reply: What is the 7-speed manual gearbox?


Contact Us About Us Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: