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-   -   991S PDK throttle hesitation from start (https://rennlist.com/forums/991/764160-991s-pdk-throttle-hesitation-from-start.html)

neanicu 08-02-2013 09:20 AM


Originally Posted by MJBird993 (Post 10655978)



I suspect that if you were to take it into the dealer for a fix, the response would be "they all do that".

No.
They'd say : " It's normal ".
:confused:

" Customer complaint : a slight hesitation from standstill
Customer thinks it's related to PDK
Technician tested the car using PIWIS and 20 min drive.
Technician's conclusion : found the behavior NORMAL and within factory specs "
:)

abiazis 08-02-2013 12:58 PM

Hate to say it but it is a design problem most likely that won't be ironed out until they re-engineer the ECU system on PDK models..............I have had 2 German cars with similar system issues - hesitation - that have been re-flashed with no or little improvement..........problem solved when the entire ECU was redesigned with their next model update......both manufacturers denied there was an issue.....sort of like the IMS fiasco class action suit on the 996....what problem, it is "normal"......and actually it is "normal" for the design they developed............"the Germans might not be right, but they are never wrong culture......."

Carrera GT 08-02-2013 04:01 PM


Originally Posted by Mike in CA (Post 10655062)
My understanding is that PDK-S in the GT3 has no "torque converter" creep off idle at all, in any mode.

I read each of the mode descriptions somewhere. Someone posted a description here, but suggested every mode omits the "automatic" creep. I think that's fine, if so. It was a bit peculiar because I read somewhere that in one mode it would never upshift automatically. I have to assume it will upshift if the throttle has depressed the "kick down" button (pushing past wide open to depress a button) which is true for Sport Plus in the 991S and the 997S. We'll know soon enough.

The GT3 has hill "hold" so it shouldn't matter too much, but if you're driving in traffic and the clutch has to transition repeatedly from engagement and slip to free, I hope Porsche made the initial engagement a very smooth transition with a partial throttle.

Between the floppy "P for Park" automatic nature of parking with the PDK (and therefore being forced to use the "whirrr ... dunk" electric parking brake, Porsche has taken away two of the things you can use to recognize a driver taking care when they use their car. You can always tell the mechanically "sympathetic" from the guys that just wrench on the parking brake as hard as they can, as if arresting the car on a double black diamond ski run, rattling the ratchet across every notch so loudly you can hear it from the other side of the shopping mall parking lot. You can appreciate a driver that can slow to a smooth halt, precisely in the parking space, no curb rash, no steering gear forced to hold the weight of the car on the shoulder of one front tire; and exit the car without it lazily flopping and rocking on the "P" transmission tooth like an absent minded cop rushing to the donut store.

Just as it should be possible to move the car forward without the transmission when and how that will happen, the driver should be able to slow to a halt without the transmission injecting brief head-nodding disturbance through a half dozen downshifts into every red light even though the car is on a closed throttle ... where's the benefit to the driver or emissions or anything to do with the car by blipping down from 7th to 2nd then shunting into 1st just to make sure nobody forgot the driver can't drive smoothly in this car.

Hopefully in future generations of the 911, the engineers and designers will pick up on these finer points and, like the simple things (the door mirrors actually on the door instead of the A pillar, the window switches on the door panel) they'll revisit the blatant mistakes of the 991 and get the 911 back on track -- literally and figuratively.

I think Porsche has to look at their position in the market. To the south, there's the Corvette, which now merits serious comparison to a Carrera, if not a GT3. Yet. Bring on the Z06 to challenge the GT3 and the ZR1 to challenge the GT2. To the north, there's the 458, which is a dramatic advance over the F430. There's soon to be public information on the 458 Monte, said by some "in the know" to be more mechanical and much lighter. Isn't that exactly what we're all asking of the GT3? But it's heavier, and more electronic. Just as Porsche makes its move on the playing board, both GM and Ferrari have pieces in position already, and the next two moves appear to be in jeopardy.

Mike in CA 08-02-2013 04:22 PM


Originally Posted by Carrera GT (Post 10656932)
I read each of the mode descriptions somewhere. Someone posted a description here, but suggested every mode omits the "automatic" creep. I think that's fine, if so. It was a bit peculiar because I read somewhere that in one mode it would never upshift automatically. I have to assume it will upshift if the throttle has depressed the "kick down" button (pushing past wide open to depress a button) which is true for Sport Plus in the 991S and the 997S. We'll know soon enough.

The GT3 has hill "hold" so it shouldn't matter too much, but if you're driving in traffic and the clutch has to transition repeatedly from engagement and slip to free, I hope Porsche made the initial engagement a very smooth transition with a partial throttle.

Between the floppy "P for Park" automatic nature of parking with the PDK (and therefore being forced to use the "whirrr ... dunk" electric parking brake, Porsche has taken away two of the things you can use to recognize a driver taking care when they use their car. You can always tell the mechanically "sympathetic" from the guys that just wrench on the parking brake as hard as they can, as if arresting the car on a double black diamond ski run, rattling the ratchet across every notch so loudly you can hear it from the other side of the shopping mall parking lot. You can appreciate a driver that can slow to a smooth halt, precisely in the parking space, no curb rash, no steering gear forced to hold the weight of the car on the shoulder of one front tire; and exit the car without it lazily flopping and rocking on the "P" transmission tooth like an absent minded cop rushing to the donut store.

Just as it should be possible to move the car forward without the transmission when and how that will happen, the driver should be able to slow to a halt without the transmission injecting brief head-nodding disturbance through a half dozen downshifts into every red light even though the car is on a closed throttle ... where's the benefit to the driver or emissions or anything to do with the car by blipping down from 7th to 2nd then shunting into 1st just to make sure nobody forgot the driver can't drive smoothly in this car.

Hopefully in future generations of the 911, the engineers and designers will pick up on these finer points and, like the simple things (the door mirrors actually on the door instead of the A pillar, the window switches on the door panel) they'll revisit the blatant mistakes of the 991 and get the 911 back on track -- literally and figuratively.

I think Porsche has to look at their position in the market. To the south, there's the Corvette, which now merits serious comparison to a Carrera, if not a GT3. Yet. Bring on the Z06 to challenge the GT3 and the ZR1 to challenge the GT2. To the north, there's the 458, which is a dramatic advance over the F430. There's soon to be public information on the 458 Monte, said by some "in the know" to be more mechanical and much lighter. Isn't that exactly what we're all asking of the GT3? But it's heavier, and more electronic. Just as Porsche makes its move on the playing board, both GM and Ferrari have pieces in position already, and the next two moves appear to be in jeopardy.

In manual mode PDK-S in the 991 GT3 will not upshift automatically under any circumstances and there is no kickdown feature. This is true regardless of whether the car is in default mode or PDK Sport. I'm 100% sure about this.

This differs from regular PDK where, as you point out, even in manual mode there is a kickdown feature, and once the kickdown is implemented PDK will continue to upshift at redline automatically until you let off the throttle. Once you let off it returns to manual mode.

I don't think that PDK-S has hill hold. Other "special functions" associated with PDK like sailing, eco-shifting, and start stop aren't included either. Likewise your comment about multiple downshifts as you come to a stop; again in manual mode the car will downshift once just as you are about to stop so as not to stall the engine. Otherwise you must downshift for yourself. This is the same way the DCT in the Ferrari 458 operates.

Speaking of the 458, almost every reviewer so far has compared the 991 GT3 to the 458 very favorably, saying it will have comparable, if not better, performance at a price that's $100K less. If true, that sounds like pretty decent market positioning to me. As you say, we'll know soon enough.

neanicu 08-02-2013 04:52 PM


Originally Posted by Carrera GT (Post 10656932)

I read each of the mode descriptions somewhere. Someone posted a description here, but suggested every mode omits the "automatic" creep. I think that's fine, if so. It was a bit peculiar because I read somewhere that in one mode it would never upshift automatically. I have to assume it will upshift if the throttle has depressed the "kick down" button (pushing past wide open to depress a button) which is true for Sport Plus in the 991S and the 997S. We'll know soon enough.

The GT3 has hill "hold" so it shouldn't matter too much, but if you're driving in traffic and the clutch has to transition repeatedly from engagement and slip to free, I hope Porsche made the initial engagement a very smooth transition with a partial throttle.

Between the floppy "P for Park" automatic nature of parking with the PDK (and therefore being forced to use the "whirrr ... dunk" electric parking brake, Porsche has taken away two of the things you can use to recognize a driver taking care when they use their car. You can always tell the mechanically "sympathetic" from the guys that just wrench on the parking brake as hard as they can, as if arresting the car on a double black diamond ski run, rattling the ratchet across every notch so loudly you can hear it from the other side of the shopping mall parking lot. You can appreciate a driver that can slow to a smooth halt, precisely in the parking space, no curb rash, no steering gear forced to hold the weight of the car on the shoulder of one front tire; and exit the car without it lazily flopping and rocking on the "P" transmission tooth like an absent minded cop rushing to the donut store.

Just as it should be possible to move the car forward without the transmission when and how that will happen, the driver should be able to slow to a halt without the transmission injecting brief head-nodding disturbance through a half dozen downshifts into every red light even though the car is on a closed throttle ... where's the benefit to the driver or emissions or anything to do with the car by blipping down from 7th to 2nd then shunting into 1st just to make sure nobody forgot the driver can't drive smoothly in this car.

:roflmao:
Brilliant writing as usual CarreraGT!
:thumbup:

Carrera GT 08-02-2013 05:08 PM


Originally Posted by Mike in CA (Post 10656985)
In manual mode PDK-S in the 991 GT3 will not upshift automatically under any circumstances and there is no kickdown feature. This is true regardless of whether the car is in default mode or PDK Sport. I'm 100% sure about this.

This differs from regular PDK where, as you point out, even in manual mode there is a kickdown feature, and once the kickdown is implemented PDK will continue to upshift at redline automatically until you let off the throttle. Once you let off it returns to manual mode.

I don't think that PDK-S has hill hold. Other "special functions" associated with PDK like sailing, eco-shifting, and start stop aren't included either. Likewise your comment about multiple downshifts as you come to a stop; again in manual mode the car will downshift once just as you are about to stop so as not to stall the engine. Otherwise you must downshift for yourself. This is the same way the DCT in the Ferrari 458 operates.

Speaking of the 458, almost every reviewer so far has compared the 991 GT3 to the 458 very favorably, saying it will have comparable, if not better, performance at a price that's $100K less. If true, that sounds like pretty decent market positioning to me. As you say, we'll know soon enough.

Just so long as there's the equivalent of a Sport Plus mode so that PDK makes all the right decisions to upshift and downshift for best possible power to the ground, best possible throttle response, best possible torque response. I shake my head when I see journo's and "test" drivers running acceleration tests and they paddle the upshift -- if they want best possible performance from the car, it has to be the computers timing the perfect upshift for the conditions. A tiny headwind or uphill grade and the computers should adjust to upshift into the meat of the torque curve, a little tail breeze or downhill and the computer can make the calculations to upshift screaming into the last ignition pulse and the last crank rotation at the redline, and the driver can keep eyes and brain on steering the line.

If PDK is now smart enough to go to open clutches as the car slows under brakes during calm driving, that's great. I read somewhere either the next iteration of the 911 or the Panamera software will also stop the engine if the car is slowing, as if to a halt at traffic lights (something like 8 mph with brake applied.) That simple logic update would avoid most of the head-nodding and shuddering and wrong-footed mistakes of PDK in the 991.

Mike in CA 08-02-2013 05:20 PM


Originally Posted by Carrera GT (Post 10657100)
Just so long as there's the equivalent of a Sport Plus mode so that PDK makes all the right decisions to upshift and downshift for best possible power to the ground, best possible throttle response, best possible torque response. I shake my head when I see journo's and "test" drivers running acceleration tests and they paddle the upshift -- if they want best possible performance from the car, it has to be the computers timing the perfect upshift for the conditions. A tiny headwind or uphill grade and the computers should adjust to upshift into the meat of the torque curve, a little tail breeze or downhill and the computer can make the calculations to upshift screaming into the last ignition pulse and the last crank rotation at the redline, and the driver can keep eyes and brain on steering the line.

If PDK is now smart enough to go to open clutches as the car slows under brakes during calm driving, that's great. I read somewhere either the next iteration of the 911 or the Panamera software will also stop the engine if the car is slowing, as if to a halt at traffic lights (something like 8 mph with brake applied.) That simple logic update would avoid most of the head-nodding and shuddering and wrong-footed mistakes of PDK in the 991.

PDK-S in auto mode makes decisions exactly the way you describe, with PDK-Sport being the equivalent of Sport Plus and taking the engine all the way to redline before upshifting. The difference being that those upshifts in the GT3 now happen at 9000 rpm. :)

neanicu 08-02-2013 05:29 PM

In the end,what's different in the PDK-S than PDK in terms of internals?
Shorter gear ratios...we know...and software...

neanicu 08-02-2013 05:38 PM

Maybe they'll use the PDK-S software in the 2nd gen PDK and this hesitation will go away...

Mike in CA 08-02-2013 06:01 PM


Originally Posted by neanicu (Post 10657171)
In the end,what's different in the PDK-S than PDK in terms of internals?
Shorter gear ratios...we know...and software...

The PDK-S differences we know:

shorter ratios
shorter shift times <100ms
top speed achieved in 7th
no crawl from idle in either auto or manual
no buffering of engine torque between shifts (Porsche calls it "torque overshoot")
just the two sport modes (no default eco shifting mode)
a true manual shift mode with no auto kickdown and auto upshifting at redline
elimination of special features (sailing, start stop, etc.)
shorter and more tactile paddle operation
reversed console stick operation with a revised stronger spring
lighter weight (a kilo or two IIRC)

As far as specific internal changes (size of clutches, mods to the geartrain, materials etc.) I'm not aware of any published info about that. FWIW, in one of the recent reviews, Porsche has claimed to have done 1000+ launch control starts to a PDK-S gearbox without failure.

neanicu 08-02-2013 06:28 PM


Originally Posted by Mike in CA (Post 10657259)

The PDK-S differences we know:

shorter ratios
shorter shift times <100ms
top speed achieved in 7th
no crawl from idle in either auto or manual
no buffering of engine torque between shifts
just the two sport modes (no default eco shifting mode)
a true manual shift mode with no auto kickdown and auto upshifting at redline
elimination of special features (sailing, start stop, etc.)
shorter and more tactile paddle operation
reversed console stick operation with a revised stronger spring
lighter weight (a kilo or two IIRC)

As far as specific internal changes (size of clutches, mods to the geartrain, materials etc.) I'm not aware of any published info about that. FWIW, in one of the recent reviews, Porsche has claimed to have done 1000+ launch control starts to a PDK-S gearbox without failure.

Thanks Mike!
I pretty much knew all of these features,I was wondering if someone would have more information about internals. I guess we won't know more until someone decides to disassemble both and see the differences. Seeing how Porsche decided to change their strategy even with the GT department to make more profit(I wonder if VW had anything to do with it...), I wouldn't be surprised if PDK-S internals are not all that different from PDK's internals,in which case a PDK.2 so called " update " will come up pretty soon.

SanibelSpeed 08-02-2013 06:54 PM

So, is this hesitation problem something that everyone is affected by or are recent production cars not having this issue? All I've read about the PDK is that it's sublime but this hesitation issue has become a subject out of the blue in just the past month. Where has everyone been the past year that this subject only just now surfaces?

chuckbdc 08-02-2013 07:02 PM


Originally Posted by SanibelSpeed (Post 10657378)
So, is this hesitation problem something that everyone is affected by or are recent production cars not having this issue? All I've read about the PDK is that it's sublime but this hesitation issue has become a subject out of the blue in just the past month. Where has everyone been the past year that this subject only just now surfaces?

Got mine in April 2012 and it has never hesitated.

SanibelSpeed 08-02-2013 07:07 PM

That's good to know, Chuck. Maybe a poll of the membership can determine how many are and how many aren't affected.

Harold1898 08-02-2013 10:59 PM

Got mine three weeks ago and no hesitation.


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