pdcc failure
08-13-2014, 11:23 PM
#16
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Can you tell us from your g meter how many g's you were pulling? Since every post is about cornering and pdcc faults, it may be too much load in the corners for the hydraulic pump to overcome? It may also be a combination of g force and a bump or angle that the pump has to overcome in which case that's an engineering oversight. I have pulled 1.09g in my 991 C4S and not had this problem yet. Any insight?
08-13-2014, 11:28 PM
#17
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Agreed. At my 1.09g I felt the rear end giggle and I have to say that if the pdcc failed I would have probably been in the guard rail - so that's why I'm wondering!!!
08-14-2014, 12:57 AM
#18
PDCC is hydraulic, so no way the force is ever too great for it to operate. It is after all designed to pre-load the anti-roll bar. Think about it.
A more likely culprit is range of motion. According to this article by Bart at Elephant Racing PDCC has a range of 50mm. https://rennlist.com/forums/991/8287...-overview.html
Ultimately, the real reason is of course product liability.
No worries, Weim. When PDCC stops like this the car handles just fine, only with more body roll. As disconcerting as this is bound to feel, it definitely will not have you sliding into the guard rail. Quite the opposite. The car will still be able to corner just as hard- harder even, more than likely- but it will feel so dramatically different that you will be unable to stop yourself from slowing down. Which I'm sure is exactly what they had in mind.
A more likely culprit is range of motion. According to this article by Bart at Elephant Racing PDCC has a range of 50mm. https://rennlist.com/forums/991/8287...-overview.html
Ultimately, the real reason is of course product liability.
No worries, Weim. When PDCC stops like this the car handles just fine, only with more body roll. As disconcerting as this is bound to feel, it definitely will not have you sliding into the guard rail. Quite the opposite. The car will still be able to corner just as hard- harder even, more than likely- but it will feel so dramatically different that you will be unable to stop yourself from slowing down. Which I'm sure is exactly what they had in mind.
08-14-2014, 01:11 AM
#19
The system needs to max out load and hold if necessary. A steady state maxing out and holding is much better than shutting down mid stream, that is the worst possible scenario for a driver running the car on the edge of its limits.
I wonder if it is not so much maxing out load and really a situation where it can't handle a certain combination of inputs .We have all at one time or another hacked at the keyboard and mouse randomly and froze the computer and had to reboot the system. Instead of deflating the system it should default to stiffing up and wait for a restart to reboot.
How does the GT3 handle the same same situation it must be under more stress?
Chuck I just read your post, if I understand what you are saying it is working as designed?
I wonder if it is not so much maxing out load and really a situation where it can't handle a certain combination of inputs .We have all at one time or another hacked at the keyboard and mouse randomly and froze the computer and had to reboot the system. Instead of deflating the system it should default to stiffing up and wait for a restart to reboot.
How does the GT3 handle the same same situation it must be under more stress?
Chuck I just read your post, if I understand what you are saying it is working as designed?
Last edited by wanderfalke; 08-14-2014 at 01:36 AM.
08-14-2014, 01:30 AM
#20
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The system needs to max out load and hold if necessary. It would be better if it could handle more load but maxing out and holding is much better than shutting down mid stream, that is the worst possible scenario.
I wonder if it is not so much maxing out load and really a situation where it can't handle a certain combination of inputs .
We have all at one time or another hacked at the keyboard and mouse randomly and froze the computer and had to reboot the system. Instead of deflating the system it should default to stiffing up and wait for a restart to reboot.
How does the GT3 handle the same same situation it must be under more stress.
I wonder if it is not so much maxing out load and really a situation where it can't handle a certain combination of inputs .
We have all at one time or another hacked at the keyboard and mouse randomly and froze the computer and had to reboot the system. Instead of deflating the system it should default to stiffing up and wait for a restart to reboot.
How does the GT3 handle the same same situation it must be under more stress.
08-14-2014, 02:07 AM
#21
08-14-2014, 03:54 AM
#22
The system needs to max out load and hold if necessary. A steady state maxing out and holding is much better than shutting down mid stream, that is the worst possible scenario for a driver running the car on the edge of its limits.
I wonder if it is not so much maxing out load and really a situation where it can't handle a certain combination of inputs .We have all at one time or another hacked at the keyboard and mouse randomly and froze the computer and had to reboot the system. Instead of deflating the system it should default to stiffing up and wait for a restart to reboot.
How does the GT3 handle the same same situation it must be under more stress?
Chuck I just read your post, if I understand what you are saying it is working as designed?
I wonder if it is not so much maxing out load and really a situation where it can't handle a certain combination of inputs .We have all at one time or another hacked at the keyboard and mouse randomly and froze the computer and had to reboot the system. Instead of deflating the system it should default to stiffing up and wait for a restart to reboot.
How does the GT3 handle the same same situation it must be under more stress?
Chuck I just read your post, if I understand what you are saying it is working as designed?
Porsche has designed the 991 as a street car- a very high performance street car much more at home on a track than most, but still a street car. As such PDCC serves both to improve handling and ride (allowing a softer bar improves ride by reducing effective spring rate) in about equal proportions. This is borne out in the fact people are having these problems only under fairly harsh extremes- for the most part max cornering combined with compressive loading.
So what are the risks? Without PDCC the car reverts to exactly the way a non-PDCC car would handle, except with a bit more body roll because the PDCC car uses a softer bar. How bad is that? Not bad at all! Of course its going to FEEL awful, like I believe it was drcollie posted, or what I described as hitting a wall of water. (He had both PDCC AND Sport+ go on him.)
Porsche could have designed PDCC to encompass track driving, but where to draw the line? Track driving with a wanna-be at the wheel? Or with an advanced driver? Track with R-comps? Slicks? Aftermarket wheels, camber, and slicks? Bear in mind, each of these choices means matching not only PDCC to expected body roll, but a whole host of related suspension parameters. Considering how many cars are tracked, how long it took for these problems to show up, and how infrequently it seems to be happening, I'd say they just about nailed it.
Now the product liability angle. They could have engineered PDCC to work right up to its max range, at which point it would just stop extending/retracting, leaving just the bar to control roll. Which if we limit ourselves to looking at cars being driven on the street (and from our point of view) would be just fine. But Porsche can't control what people do to their cars or how they drive them. Recall how many posts you've seen from people wanting to max out camber, wheels and tires, on and on. (And that's just the ones who post! Go to a track and see what shows up!) So the suits walk down the hall and say to the engineers: make it default to Normal until they shut it off.
Of course this is all conjecture. Nobody at Porsche walked me through this. Its just that, understanding suspension setup, handling and Porsche in general, its hard to see it coming out any other way.
08-14-2014, 04:18 AM
#23
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***WARNING: BEWARE OF PDCC ON TRACK***
Tuesday was my 1st day at NHMS testing new C4S with 3,000 miles. I spent the first two run sessions SLOWLY ramping up my speed and by the 3rd session I was running at about 7/10's when I suddenly lost control in turn 3 near the wall as I made the hard uphill transition to the outfield course.
My suspension seemed to "let go" pitching the car suddenly. I noticed the orange PDCC fault message on the MFD: "Possible to drive on carefully". I suspect that the light may have come on exiting the prior turn which also had a hard transition between the infield and the track.
The PDCC system subsequently reset upon engine restart. However, my track days are on hold until Porsche comes up with an explanation and fix. I will have my local dealer pull the code & log the error so PAG has a record.
Tuesday was my 1st day at NHMS testing new C4S with 3,000 miles. I spent the first two run sessions SLOWLY ramping up my speed and by the 3rd session I was running at about 7/10's when I suddenly lost control in turn 3 near the wall as I made the hard uphill transition to the outfield course.
My suspension seemed to "let go" pitching the car suddenly. I noticed the orange PDCC fault message on the MFD: "Possible to drive on carefully". I suspect that the light may have come on exiting the prior turn which also had a hard transition between the infield and the track.
The PDCC system subsequently reset upon engine restart. However, my track days are on hold until Porsche comes up with an explanation and fix. I will have my local dealer pull the code & log the error so PAG has a record.
Can you tell us from your g meter how many g's you were pulling? Since every post is about cornering and pdcc faults, it may be too much load in the corners for the hydraulic pump to overcome? It may also be a combination of g force and a bump or angle that the pump has to overcome in which case that's an engineering oversight. I have pulled 1.09g in my 991 C4S and not had this problem yet. Any insight?
08-14-2014, 08:44 AM
#24
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Can you tell us from your g meter how many g's you were pulling? Since every post is about cornering and pdcc faults, it may be too much load in the corners for the hydraulic pump to overcome? It may also be a combination of g force and a bump or angle that the pump has to overcome in which case that's an engineering oversight. I have pulled 1.09g in my 991 C4S and not had this problem yet. Any insight?
08-14-2014, 09:23 AM
#25
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Right. I could've expanded several points but thought better of it. Reading subsequent comments, maybe not. There's a lot of basic suspension misunderstandings, even more regarding PDCC.
Porsche has designed the 991 as a street car- a very high performance street car much more at home on a track than most, but still a street car. As such PDCC serves both to improve handling and ride (allowing a softer bar improves ride by reducing effective spring rate) in about equal proportions. This is borne out in the fact people are having these problems only under fairly harsh extremes- for the most part max cornering combined with compressive loading.
So what are the risks? Without PDCC the car reverts to exactly the way a non-PDCC car would handle, except with a bit more body roll because the PDCC car uses a softer bar. How bad is that? Not bad at all! Of course its going to FEEL awful, like I believe it was drcollie posted, or what I described as hitting a wall of water. (He had both PDCC AND Sport+ go on him.)
Porsche could have designed PDCC to encompass track driving, but where to draw the line? Track driving with a wanna-be at the wheel? Or with an advanced driver? Track with R-comps? Slicks? Aftermarket wheels, camber, and slicks? Bear in mind, each of these choices means matching not only PDCC to expected body roll, but a whole host of related suspension parameters. Considering how many cars are tracked, how long it took for these problems to show up, and how infrequently it seems to be happening, I'd say they just about nailed it.
Now the product liability angle. They could have engineered PDCC to work right up to its max range, at which point it would just stop extending/retracting, leaving just the bar to control roll. Which if we limit ourselves to looking at cars being driven on the street (and from our point of view) would be just fine. But Porsche can't control what people do to their cars or how they drive them. Recall how many posts you've seen from people wanting to max out camber, wheels and tires, on and on. (And that's just the ones who post! Go to a track and see what shows up!) So the suits walk down the hall and say to the engineers: make it default to Normal until they shut it off.
Of course this is all conjecture. Nobody at Porsche walked me through this. Its just that, understanding suspension setup, handling and Porsche in general, its hard to see it coming out any other way.
Porsche has designed the 991 as a street car- a very high performance street car much more at home on a track than most, but still a street car. As such PDCC serves both to improve handling and ride (allowing a softer bar improves ride by reducing effective spring rate) in about equal proportions. This is borne out in the fact people are having these problems only under fairly harsh extremes- for the most part max cornering combined with compressive loading.
So what are the risks? Without PDCC the car reverts to exactly the way a non-PDCC car would handle, except with a bit more body roll because the PDCC car uses a softer bar. How bad is that? Not bad at all! Of course its going to FEEL awful, like I believe it was drcollie posted, or what I described as hitting a wall of water. (He had both PDCC AND Sport+ go on him.)
Porsche could have designed PDCC to encompass track driving, but where to draw the line? Track driving with a wanna-be at the wheel? Or with an advanced driver? Track with R-comps? Slicks? Aftermarket wheels, camber, and slicks? Bear in mind, each of these choices means matching not only PDCC to expected body roll, but a whole host of related suspension parameters. Considering how many cars are tracked, how long it took for these problems to show up, and how infrequently it seems to be happening, I'd say they just about nailed it.
Now the product liability angle. They could have engineered PDCC to work right up to its max range, at which point it would just stop extending/retracting, leaving just the bar to control roll. Which if we limit ourselves to looking at cars being driven on the street (and from our point of view) would be just fine. But Porsche can't control what people do to their cars or how they drive them. Recall how many posts you've seen from people wanting to max out camber, wheels and tires, on and on. (And that's just the ones who post! Go to a track and see what shows up!) So the suits walk down the hall and say to the engineers: make it default to Normal until they shut it off.
Of course this is all conjecture. Nobody at Porsche walked me through this. Its just that, understanding suspension setup, handling and Porsche in general, its hard to see it coming out any other way.
REALLY? You seem OK with this... WOW!!!
Come on, please... This is crazy... Where is the warning NOT to use it on the track? Porsche needs to address a different hardware or software design, plain and simple!
08-14-2014, 10:30 AM
#26
I have a CS4 that has my back when I push the limits (it covers my lack of track experience).In critical situations I want to have a predictable response, the car may be able to handle a sudden change but I would the the weak link especially the first time it failed.
930 gti guy you should have waited to post those big numbers who wants to post after that entry. :-}
I wonder how many people here bundle the ceramic brakes with the PDCC for the track. Having that warning pop up would be discouraging after spending a extra 10 k.
930 gti guy you should have waited to post those big numbers who wants to post after that entry. :-}
I wonder how many people here bundle the ceramic brakes with the PDCC for the track. Having that warning pop up would be discouraging after spending a extra 10 k.
08-14-2014, 04:22 PM
#28
Chuck is correct about the cornering g-force, driving in the city, I barely get 1.04 g,
I just got another failure 3 days ago which I check the meter and it show .9 g.
He is also correct that the 991, even with pdcc failure, drives fine, only major diff is the sports plus can't be turn on. Other than that, it drives normal like any other time without the sport plus activated.
Like I said in other post, sometime it happen, sometime it doesn't. I tried repeatedly go thru the same corner few times in the same manner on the same day that I have the pdcc failure to try to duplicate it again but it won't.
So there, I could live with it but....its just not right.
I just got another failure 3 days ago which I check the meter and it show .9 g.
He is also correct that the 991, even with pdcc failure, drives fine, only major diff is the sports plus can't be turn on. Other than that, it drives normal like any other time without the sport plus activated.
Like I said in other post, sometime it happen, sometime it doesn't. I tried repeatedly go thru the same corner few times in the same manner on the same day that I have the pdcc failure to try to duplicate it again but it won't.
So there, I could live with it but....its just not right.
08-14-2014, 08:57 PM
#30
I'll give it little more time and see how often it comes on and start log and take pics.
Gonna jack it up and just do thorough check underneath, before I take it in, make sure nothing is out of place or worn/damaged. I just have a vibe everytime I take my vehicle in for service to dealer, any dealer, because of past experience and the things I know now.
Gonna jack it up and just do thorough check underneath, before I take it in, make sure nothing is out of place or worn/damaged. I just have a vibe everytime I take my vehicle in for service to dealer, any dealer, because of past experience and the things I know now.