LN bearing service life and/or failures
#31
Here is some info on the bearings:
Single row replaceable bearing 6204 (Early 2005)
ID = 20mm
OD = 47mm
Dynamic Load = 12,800 N
Static Load = 6,600 N
Limiting Speed = 11,000 RPMs with grease
Single Row Non-Replaceable bearing 6305 (Late 2005 - on)
ID = 25mm
OD = 62mm
Dynamic Load = 23,600 N
Static Load = 12,100 N
Limiting Speed = 12,000 RPMs with grease
The load rating of 6305 (the non-replaceable one) has been increased by nearly 85% compared to 6204.
The 6305 is larger therefore more of the bearing is submerged in engine lubricant all other things equal.
Seems like a substantial change in design.
Cheers,
=L=
Single row replaceable bearing 6204 (Early 2005)
ID = 20mm
OD = 47mm
Dynamic Load = 12,800 N
Static Load = 6,600 N
Limiting Speed = 11,000 RPMs with grease
Single Row Non-Replaceable bearing 6305 (Late 2005 - on)
ID = 25mm
OD = 62mm
Dynamic Load = 23,600 N
Static Load = 12,100 N
Limiting Speed = 12,000 RPMs with grease
The load rating of 6305 (the non-replaceable one) has been increased by nearly 85% compared to 6204.
The 6305 is larger therefore more of the bearing is submerged in engine lubricant all other things equal.
Seems like a substantial change in design.
Cheers,
=L=
#32
Thanks!
I like facts much more than just tales.
Yes,
http://www.hartech.org/buyers.html
Guide # 5 explains it all and it is very technical. Enjoy reading.
In a way, the IMS issue is a blessing for 997. In makes the owners aware of proper and frequent maintenance.
Cheers,
=L=
I like facts much more than just tales.
http://www.hartech.org/buyers.html
Guide # 5 explains it all and it is very technical. Enjoy reading.
In a way, the IMS issue is a blessing for 997. In makes the owners aware of proper and frequent maintenance.
Cheers,
=L=
#33
Thanks Luster!
Thanks!
I like facts much more than just tales.
Yes,
http://www.hartech.org/buyers.html
Guide # 5 explains it all and it is very technical. Enjoy reading.
In a way, the IMS issue is a blessing for 997. In makes the owners aware of proper and frequent maintenance.
Cheers,
=L=
I like facts much more than just tales.
Yes,
http://www.hartech.org/buyers.html
Guide # 5 explains it all and it is very technical. Enjoy reading.
In a way, the IMS issue is a blessing for 997. In makes the owners aware of proper and frequent maintenance.
Cheers,
=L=
#35
Why the larger bearing fails less is due to it being a more substantial piece of kit, that is, because it is larger. The increased load rating is a consequence of the increase in size, and not really much of a factor in this application other than that the stud is less prone to snap. If the cage disintegrates and sends the ***** spewing into the engine, the same catastrophic failure would occur as with the smaller bearing.
Where the larger bearing is at a disadvantage is in so-called high-performance driving. Due to the increased diameter, each ball travels farther within the race with each revolution. So if the bearing is receiving inadequate lubrication and/or there is grease mixed with debris inside forming a grinding paste, the larger bearing will wear at an accelerated pace compared with the smaller bearing. At that point it is anyone's guess which will fail sooner. Perhaps the increased size of the later bearing is enough to keep it together. The fact is, of all possible solutions, Porsche chose the cheapest one, evidenced by the fact they used the same case and did not enlarge the portal enough that the new bearing can be extracted as the old ones could.
By the way, Hartech makes one extremely important observation about replacing an IMS bearing in-situ: If the OEM bearing has failed (or is in the final stage before failure) there can be significant damage and debris within the engine that a replacement bearing--no matter how well-engineered that replacement may be--may well fail prematurely. LN acknowledges that, especially since theirs is an open design, and cautions against retrofitting when the OEM bearing has failed or if upon inspection it show signs of breakdown.
My opinion based on engineering principles, is that the LN retrofit is best done prophylactically, whilst the OEM bearing is still in pristine condition. That and meticulous installation protocols should give the retrofit at least as fair a chance of long-term survival as the later, larger OEM bearing, if not more.
#36
By the way, Hartech makes one extremely important observation about replacing an IMS bearing in-situ: If the OEM bearing has failed (or is in the final stage before failure) there can be significant damage and debris within the engine that a replacement bearing--no matter how well-engineered that replacement may be--may well fail prematurely. LN acknowledges that, especially since theirs is an open design, and cautions against retrofitting when the OEM bearing has failed or if upon inspection it show signs of breakdown.
That's why they suggest full flow oil filter with their adapter.
So, I guess we are back to proper and frequent maintenance.
#37
I have a close contact from the racing side of Porsche who explained the IMS issue. The original failure rate was 5% because the stud on the end of the IMS shaft was fragile and would brake off. Once broken it allowed the IMS to oscillate and this extra movement caused the IMS bearing to fail. The bearing was not the source of the failure rather it was a symptom. In 2001 the stud on the end of the IMS was beefed up and failure rates went to 1%. They continued to improve the bearing and reduced failure rates down to 1/2% until the IMS design was abandoned. Bottom line line is an engine 2002+ with an IMS has a 1%< chance of a catastrophic failure and like someone posted earlier nothing is bullet proof. I bet any car has at least 1% chance of a terminal failure for something - this topic remains over blown.
#38
Thanks for that balanced view. I think you're right about "Over Blown Topic"
I have a close contact from the racing side of Porsche who explained the IMS issue. The original failure rate was 5% because the stud on the end of the IMS shaft was fragile and would brake off. Once broken it allowed the IMS to oscillate and this extra movement caused the IMS bearing to fail. The bearing was not the source of the failure rather it was a symptom. In 2001 the stud on the end of the IMS was beefed up and failure rates went to 1%. They continued to improve the bearing and reduced failure rates down to 1/2% until the IMS design was abandoned. Bottom line line is an engine 2002+ with an IMS has a 1%< chance of a catastrophic failure and like someone posted earlier nothing is bullet proof. I bet any car has at least 1% chance of a terminal failure for something - this topic remains over blown.
#39
Official Rennlist Snake Slayer
Rennlist Member
Rennlist Member
Joined: Dec 2009
Posts: 3,676
Likes: 4
From: Charleston, SC
From the size of the bearing ID, it appears that Porsche also increased the diameter of the shaft by 25%, at least in the bearing area. That's a rather large difference. Could be due to "overbuild" engineering, but if the shaft is larger in diameter along it's entire length, that would signifigantly reduce lash and angular forces applied to the bearing it's not designed to absorb.
I would guess the redesign involved the new bearing, and the IMS got beefed up quite a bit, too.
I would guess the redesign involved the new bearing, and the IMS got beefed up quite a bit, too.
#40
They continued to improve the bearing and reduced failure rates down to 1/2%
#42
I spent the bulk of my career working with most of the automotive manufacturers in North America. A failure rate of 0.5% on my company's product would have consistently put me in the QC manager's office. Think about it. A 0.5% failure rate is equal to 1 in 200 parts failing!
as of cracks in rods and broken off rod bolts - again, it is probably all due to possible overtorque at assembly time, in my opinion, or due to amount of detonations if owner is negligent to gas quality.
what bothers me most - when ln eng shop rebuilds those motors using all proper parts they run those motors in the grand am series and none of those enginnes ever blew. so it is possible to make those motors work fine, and apparently only difference is to put in $5K worth of proper parts - good cylinders, good rods, good bolts, $300 bearings instead off $20 ones, etc.
realistically if by now almost everybody accept the fact that this IMS bearing has a limited life span - it has to be a recall campaign similar to what vettes had and factory should pay for labor to split the block and replace this part. it is not an acceptable scenario to have this problem and just wait for a bearinng to fall apart at 70k or 80k miles on a perfectly healthy motor.
#43
Your deep-throat "from the racing side of Porsche" is wholly ignorant on the subject. Spindle breakage is not the primary cause of IMS bearing failure, and in a large number of cases it is found intact. The ***** and race wear as a result of improper and abrasive-contaminated lubricant, consequently causing failure of the ball cage. Only if a failing bearing manages, by some anomalous coalescence of factors, to run out-of-true and extremely hot for a significant amount of time without flying apart, is the spindle at risk of breaking.
#44
I spent the bulk of my career working with most of the automotive manufacturers in North America. A failure rate of 0.5% on my company's product would have consistently put me in the QC manager's office. Think about it. A 0.5% failure rate is equal to 1 in 200 parts failing!
#45
i'm curious, do you have an extended warranty? if not, you are absolutely a 'glass half full' guy. i would think it would be hard for anyone to overlook the potential of a $20k repair bill. you're clearly more of an optimist than i am.