Gen 2 9A1 Bore scoring - smoking Gun Article
02-12-2019, 09:28 PM
#3
Three Wheelin'
On would think that by now, with the 9A1 now over a decade old, these issues would be showing up with regularity. Does anyone have an estimate of % of bore-scored engines for, say 2006 997.2 3.8L engines 3 years ago, vs. the current 2009 generation of DFI engines?
02-13-2019, 07:46 AM
#4
2006 997.2 3.8L?
Current 2009 DFI?
997.2 came as MY2009 (some 2008 builds) but not 2006
997.2 are all DFI...
02-13-2019, 07:55 AM
#5
Not really ;-) I'd rather call it more of an advertorial than an actual article, creating a non existing problem to be fix IMO...
This is the first time I'm made "aware" of this issue with the 997's DFI engine(s), and knowing how things have a habit of getting turned into a "teacup in a storm" scenario in these forums (rennlist included), I'm not sold...
This is the first time I'm made "aware" of this issue with the 997's DFI engine(s), and knowing how things have a habit of getting turned into a "teacup in a storm" scenario in these forums (rennlist included), I'm not sold...
02-13-2019, 08:18 AM
#6
RL Community Team
Rennlist Member
Rennlist Member
Some examples:
.
- See this thread for some 9A1 scoring photos (1st and 3rd photos) from Hartech in the UK: http://911uk.com/viewtopic.php?t=128713
- And see here for Jake Raby’s tear down of Bronz’s engine in the US: https://rennlist.com/forums/997-foru...l#post15631340
Karl.
02-13-2019, 08:58 AM
#7
I'm by far the most up to date person on these type of subjects so I stand corrected in the sense that it's not unheard of in the 997.2. Sounds more like it falls under a general accepted car manufacturers 0.5% of fails (or whatever the accepted margin is set at) than anything else...
What I'm saying is that, advertorials like the one shared is creating more panic than any good (IMO). It's almost like we must have an issue for no apparent reason.
The 996 had the IMS and RMS issues, then the 997.1 had the borescoring and now 10 years after the MY09 997.2 we finally found some very rare bore scorings with the 997.2 so let's stir things up :-)
What I'm saying is that, advertorials like the one shared is creating more panic than any good (IMO). It's almost like we must have an issue for no apparent reason.
The 996 had the IMS and RMS issues, then the 997.1 had the borescoring and now 10 years after the MY09 997.2 we finally found some very rare bore scorings with the 997.2 so let's stir things up :-)
Last edited by Frank996; 02-14-2019 at 12:35 PM.
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02-13-2019, 11:08 AM
#8
RL Community Team
Rennlist Member
Rennlist Member
I found the article interesting too, especially since Jake has sent Bronz's injectors off for flow and spray pattern testing to see if the #1 injector is different from the others and may have caused or contributed to the scored bore due to cylinder washing.
One thing that's interesting to me is that in the NA DFI engines, it's most commonly cylinder #1 that is scored, but in this Turbo it was cylinder #6. I'm not familiar enough with the turbo setup in this generation of 997,but if one of the turbos is closest to cylinder #6, the heat from it could be a contributor to a damaged injector. If that's the case, Turbo owners might consider installing Turbo blankets on the turbos to help contain and isolate the heat.
One thing that's interesting to me is that in the NA DFI engines, it's most commonly cylinder #1 that is scored, but in this Turbo it was cylinder #6. I'm not familiar enough with the turbo setup in this generation of 997,but if one of the turbos is closest to cylinder #6, the heat from it could be a contributor to a damaged injector. If that's the case, Turbo owners might consider installing Turbo blankets on the turbos to help contain and isolate the heat.
02-13-2019, 12:38 PM
#9
It’s seemly rare, but 9A1 bore scoring is not unheard of.
Some examples:
.
- See this thread for some 9A1 scoring photos (1st and 3rd photos) from Hartech in the UK: http://911uk.com/viewtopic.php?t=128713
- And see here for Jake Raby’s tear down of Bronz’s engine in the US: https://rennlist.com/forums/997-foru...l#post15631340
Karl.
02-13-2019, 01:00 PM
#10
Three Wheelin'
Sorry, wasn't the M97 also 3.8L? I simply meant how many failures of 2006 built M97 engines in 2016 were present, vs how many of the 9A1 (2009 built) in 2019. Some statistical analysis is definitely in order, before everyone here jumps off a cliff due to the stress of potential bore scoring issues in their 9A1
02-13-2019, 01:01 PM
#11
Drifting
If Jake's posts have taught us anything it's that in most cases of bore scoring on the 9A1, the scoring is done by the piston skirt against the bore, not by failed rings. So, how can fuel wash be the root cause when the piston skirt resides behind the oil control ring?
Fuel wash affects the cylinder wall on the combustion side of the piston. In most engines, fuel wash affects the compression, or top rings. Everything behind the oil ring is being constantly re-lubed no matter which direction the piston is moving
Fuel wash affects the cylinder wall on the combustion side of the piston. In most engines, fuel wash affects the compression, or top rings. Everything behind the oil ring is being constantly re-lubed no matter which direction the piston is moving
02-13-2019, 01:10 PM
#12
Three Wheelin'
Not really ;-) I'd rather call it more of an advertorial than an actual article, creating a non existing problem to be fix IMO...
This is the first time I'm made "aware" of this issue with the 997's DFI engine(s), and knowing how things have a habit of getting turned into a "teacup in a storm" scenario in these forums (rennlist included), I'm not sold...
This is the first time I'm made "aware" of this issue with the 997's DFI engine(s), and knowing how things have a habit of getting turned into a "teacup in a storm" scenario in these forums (rennlist included), I'm not sold...
The automatic tranny on my 1993 Subaru went out, and I don't remember a storm of brown, foul-smelling objects flying through the air on an internet forum back then about the unreliability of that transmission. Perhaps I was just unlucky: the dealer had never seen one blow up. In fact, it was a real mess, as Subaru USA didn't have the correct transmission in their inventory.
There has to be 10's of thousands of 997.2 DFI engines running around. How many are documented to have bore scoring issues? Even here, were anyone with an issue is guaranteed to start a thread about it?
02-14-2019, 12:53 AM
#13
Rennlist Member
Exactly, all this is , is an unfortunate event that can happen on rare occasion. All we/they are trying to put forth is a plausible reason as to why this can happen and how maybe one can prevent it if they choose. Which is why these forums are useful. There are people with way more experience and knowledge on here than most and they are just trying to disseminate what they have found and rationalized to be the potential culprits. To dismiss or criticize them on disclosing to us what they have found is only showing your lack of knowledge and ignorance on the subject. There are no Glass houses, despite all the good one can do, **** happens , and nothing lasts forever. The more your learn , you realize the less you know. Get over it
02-14-2019, 08:50 AM
#14
Reading this and the other thread on the same topic is extremely frustrating.
I suppose people think I must be lying when I say we measured the bores that have seized (not scored) and the adjacent ones and found clearances shrunk down to less than half a thou in the areas either side of the centre thrust direction where the piston has seized (and that after over 70K and pistons also worn down a little) the next cylinder half that shrinkage and the last one no shrinkage.
They cannot have been made like that or the engines would not have lasted for over 70K.
It is entirely illogical not to understand that something has caused the clearances at the bottom of some cylinders to shrink inwards in the area immediately in line with the large section casting that also holds the main bearings.
It is also illogical when told that all 5 seized in winter and after a very short distance driving admittedly fast from cold - all sorts of other explanations that have no connection to temperature or the shrinkage come into force.
From cold a piston with half a thou clearance will seize up if the car is driven too fast too soon (and remember this is the size of the cylinder next to the one that seized). as best as we can measure w here it seized that cylinder had a couple of tenths of a thou clearance.
However - if you can accept that evidence - I openly admit that the reason for the shrinkage can be debated and there may be many explanations - and I have offered 2 related to a common and well understood phenomenon that engineers are used to managing.
Anyway, it is only my advice to warm engines up thoroughly before thrashing them - I actually will get more business if you ignore that advice - good luck everyone.
Baz
I suppose people think I must be lying when I say we measured the bores that have seized (not scored) and the adjacent ones and found clearances shrunk down to less than half a thou in the areas either side of the centre thrust direction where the piston has seized (and that after over 70K and pistons also worn down a little) the next cylinder half that shrinkage and the last one no shrinkage.
They cannot have been made like that or the engines would not have lasted for over 70K.
It is entirely illogical not to understand that something has caused the clearances at the bottom of some cylinders to shrink inwards in the area immediately in line with the large section casting that also holds the main bearings.
It is also illogical when told that all 5 seized in winter and after a very short distance driving admittedly fast from cold - all sorts of other explanations that have no connection to temperature or the shrinkage come into force.
From cold a piston with half a thou clearance will seize up if the car is driven too fast too soon (and remember this is the size of the cylinder next to the one that seized). as best as we can measure w here it seized that cylinder had a couple of tenths of a thou clearance.
However - if you can accept that evidence - I openly admit that the reason for the shrinkage can be debated and there may be many explanations - and I have offered 2 related to a common and well understood phenomenon that engineers are used to managing.
Anyway, it is only my advice to warm engines up thoroughly before thrashing them - I actually will get more business if you ignore that advice - good luck everyone.
Baz
02-14-2019, 11:39 AM
#15
RL Community Team
Rennlist Member
Rennlist Member
Certainly I and I'm sure many others appreciate you sharing your findings based on the hard evidence of the 9A1 rebuilds that Hartech has performed to date (which seems to total 5 so far if I've read correctly) - truly many thanks.
But your comment "people think I must be lying" has me a bit mystified. Apologies if I it missed but I don't believe I've seen anyone contradict you, cast aspersions, etc. about your findings in this thread or the other thread.
Why do you feel like that?
Thanks.
Karl.
