Data for Engine shudder/2500rpm issues
09-28-2014, 11:58 AM
#31
Sorry Weim.
I don't think I should have chimed in with the info I have. My car doesn't have the issue. 2013 but June build so almost a 14 by model year.
I should be clear that I'm sure the MT cars have the same issue. There just isn't as many MT cars out there and that's most likely the reason we haven't heard about it from them.
Those of you that know you have the "stumble" issue go right out and do what I said to do. He actually called it a harmonic imbalance. Again, it will be very obvious. Even in the cars where the stumble isn't as pronounced, you will notice it at a complete stop, in neutral, left foot on the brake or parking brake on.
I don't think I should have chimed in with the info I have. My car doesn't have the issue. 2013 but June build so almost a 14 by model year.
I should be clear that I'm sure the MT cars have the same issue. There just isn't as many MT cars out there and that's most likely the reason we haven't heard about it from them.
Those of you that know you have the "stumble" issue go right out and do what I said to do. He actually called it a harmonic imbalance. Again, it will be very obvious. Even in the cars where the stumble isn't as pronounced, you will notice it at a complete stop, in neutral, left foot on the brake or parking brake on.
09-28-2014, 12:34 PM
#32
Burning Brakes
2014 7MT stumble from day one. Only noticeable under light load, partial throttle opening.
09-28-2014, 01:11 PM
#33
This still doesn't explain why only some cars are affected. Presumably you drove all your cars the same so its hard to put it down to driving style- especially since they went stumble/smooth/stumble. Still, you may have put your finger on it: something about Variocam-plus.
09-28-2014, 01:58 PM
#34
Burning Brakes
Just tried the slow revving in neutral and didn't notice anything. I'll try it again later. For the gear surgeon/engineers out there, IF a car has this issue and IF it's crankshaft related, is there any long term risk to engine longevity? Does this cause extra wear on bearings or anything else?
I'd like to keep the car for a long time, but if there's an elevated risk of dropping an engine after warranty (and maybe even a rejected core!!!) then I'd have to get rid of it and do so prior to warranty expiration in early 2018.
If, OTOH, I end up having this issue but the only issue is the slight hesitation under light loads at that exact rpm range but it does NOT present an elevated risk to long term high mileage engine longevity, then I'd be fine with keeping it. Although is still hope for an in warranty fix. The GT3 guys got extremely well taken care of. We better not have drawn a 996 style short straw.
I'd like to keep the car for a long time, but if there's an elevated risk of dropping an engine after warranty (and maybe even a rejected core!!!) then I'd have to get rid of it and do so prior to warranty expiration in early 2018.
If, OTOH, I end up having this issue but the only issue is the slight hesitation under light loads at that exact rpm range but it does NOT present an elevated risk to long term high mileage engine longevity, then I'd be fine with keeping it. Although is still hope for an in warranty fix. The GT3 guys got extremely well taken care of. We better not have drawn a 996 style short straw.
09-28-2014, 02:17 PM
#35
Searching Variocam-plus hesitation turns up lots of stuff that sounds familiar.
https://rennlist.com/forums/997-foru...opionions.html
http://pedrosboard.com/read.php?7,28629,28629
https://rennlist.com/forums/997-foru...opionions.html
http://pedrosboard.com/read.php?7,28629,28629
09-28-2014, 03:28 PM
#36
Rennlist Member
Thanks chuck911. Familiar indeed! The switchover mechanism on the variocam looks binary (and quite mechanically crude!) and so it may be that simple transition which is at the root of these reports... But I still don't understand why some folks (or volks) get it starting later on in the cars life...
09-29-2014, 04:23 PM
#37
Drifting
09-29-2014, 05:15 PM
#38
Rennlist Member
Sure it's helpful.
Its a quirk that you won't be able to have your dealer resolve regardless of how much data you give them.
I understand many of you that are experiencing it are upset. I didn't say my car doesn't have the issue to pi** anyone off. Why would I try to be informative and condescending in the same thread?
Those of you who read my posts can see I'm always sharing positive reinforcement.
It's not a fuel delivery issue regardless of how the issue is being described here in the thread. I say issue and not a problem because Porsche doesn't consider it a problem. Obviously it's occurrence in some cars is troublesome to owners experiencing it and that's why it's being discussed.
The only reason I said I shouldn't have even posted in the first place is because Weim asked for data from owners and while I've driven a few cars now that are experiencing the stumble as it's called my particular car isn't experiencing it so I don't have my own data regarding it.
I was only offering up an explanation I was given from a conversation I had with someone that recently returned to the states from an engineering internship in Stuttgart.
The description of fuel delivery loss, fishing line tug are accurate descriptions as to what's happening in some cars. What I'm saying is ALL of your cars including mine have the same fuel management system software. It's not a fuel issue. It's mechanical. I already posted the reason why some cars experience it.
Not every engine is created equal and even though Porsche is an amazing auto manufacturer they are not perfect.
Look at the GT3 fiasco and the 918 that burned up last night.
And again, the YouTube post of the guy in his shorts complaining about his sluggish throttle response is a completely different issue. Unfortunately what he's complaining about is the nature of how the PDK works.
Carry on boys.
Its a quirk that you won't be able to have your dealer resolve regardless of how much data you give them.
I understand many of you that are experiencing it are upset. I didn't say my car doesn't have the issue to pi** anyone off. Why would I try to be informative and condescending in the same thread?
Those of you who read my posts can see I'm always sharing positive reinforcement.
It's not a fuel delivery issue regardless of how the issue is being described here in the thread. I say issue and not a problem because Porsche doesn't consider it a problem. Obviously it's occurrence in some cars is troublesome to owners experiencing it and that's why it's being discussed.
The only reason I said I shouldn't have even posted in the first place is because Weim asked for data from owners and while I've driven a few cars now that are experiencing the stumble as it's called my particular car isn't experiencing it so I don't have my own data regarding it.
I was only offering up an explanation I was given from a conversation I had with someone that recently returned to the states from an engineering internship in Stuttgart.
The description of fuel delivery loss, fishing line tug are accurate descriptions as to what's happening in some cars. What I'm saying is ALL of your cars including mine have the same fuel management system software. It's not a fuel issue. It's mechanical. I already posted the reason why some cars experience it.
Not every engine is created equal and even though Porsche is an amazing auto manufacturer they are not perfect.
Look at the GT3 fiasco and the 918 that burned up last night.
And again, the YouTube post of the guy in his shorts complaining about his sluggish throttle response is a completely different issue. Unfortunately what he's complaining about is the nature of how the PDK works.
Carry on boys.
09-29-2014, 05:30 PM
#39
IF a car has this issue and IF it's crankshaft related, is there any long term risk to engine longevity? Does this cause extra wear on bearings or anything else?
I'd like to keep the car for a long time, but if there's an elevated risk of dropping an engine after warranty (and maybe even a rejected core!!!) then I'd have to get rid of it and do so prior to warranty expiration in early 2018.
I'd like to keep the car for a long time, but if there's an elevated risk of dropping an engine after warranty (and maybe even a rejected core!!!) then I'd have to get rid of it and do so prior to warranty expiration in early 2018.
09-29-2014, 06:37 PM
#41
Burning Brakes
09-29-2014, 11:08 PM
#42
I would have thought a 991 Cab with pedal extenders would fly off the lot….
Anyway, his car was running like a top, until the mains went. Other end of the scale, my first car was a 1972 240-Z that ran so far out of balance every time I revved past 5000 RPM I half expected to hear Scotty saying She canna take any more cap'n' she's breakin' up! I mean you look in the rear view mirror its just a blur. But when I rebuilt it at over 100k miles the mains were fine. (Balanced, it rev's to redline smooth as can be.) So, balance or out of balance, it really don't matter. Until the bell tolls.
Anyway, his car was running like a top, until the mains went. Other end of the scale, my first car was a 1972 240-Z that ran so far out of balance every time I revved past 5000 RPM I half expected to hear Scotty saying She canna take any more cap'n' she's breakin' up! I mean you look in the rear view mirror its just a blur. But when I rebuilt it at over 100k miles the mains were fine. (Balanced, it rev's to redline smooth as can be.) So, balance or out of balance, it really don't matter. Until the bell tolls.
09-29-2014, 11:40 PM
#43
Rennlist Member
I would have thought a 991 Cab with pedal extenders would fly off the lot…. Anyway, his car was running like a top, until the mains went. Other end of the scale, my first car was a 1972 240-Z that ran so far out of balance every time I revved past 5000 RPM I half expected to hear Scotty saying She canna take any more cap'n' she's breakin' up! I mean you look in the rear view mirror its just a blur. But when I rebuilt it at over 100k miles the mains were fine. (Balanced, it rev's to redline smooth as can be.) So, balance or out of balance, it really don't matter. Until the bell tolls.
09-30-2014, 12:25 AM
#44
Burning Brakes
Okay, I finally noticed it on mine. '14 with 7MT. Only with light load at 2500rpm. I never really noticed it until I read it on the forums. Truth is I never go at light load enough to notice. Anyways, hope they fix it.
09-30-2014, 01:46 AM
#45
Burning Brakes
Lol I realize that any engine can go any time etc etc etc.
I'm just wondering if a potential crankshaft "issue not problem" could reasonably be credited with an elevated risk.
IMO if a well taken care of engine (proper warm up, cool down, oil changes and scheduled maintenance) should last an absolute minimum of 150k miles. I'd expect that from any modern manufacturer or brand period, and if not then something's severely wrong. 200-300k are reasonable for a quality well engineered engine IMO.
Yes the bell can toll (really?) for any engine ever made in history. But that's meaningless mechanical sophistry to say that.
If this "issue" is crankshaft related, can it reasonably effect engine longevity in general?
I'm just wondering if a potential crankshaft "issue not problem" could reasonably be credited with an elevated risk.
IMO if a well taken care of engine (proper warm up, cool down, oil changes and scheduled maintenance) should last an absolute minimum of 150k miles. I'd expect that from any modern manufacturer or brand period, and if not then something's severely wrong. 200-300k are reasonable for a quality well engineered engine IMO.
Yes the bell can toll (really?) for any engine ever made in history. But that's meaningless mechanical sophistry to say that.
If this "issue" is crankshaft related, can it reasonably effect engine longevity in general?