Very informative IMS discussion
#3
Advanced
Join Date: Feb 2011
Location: Montreal, Canada
Posts: 95
Likes: 0
Received 0 Likes
on
0 Posts
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Read ALL the posts by Bill Ryan ("casperlabs') in this thread (not just the one on the linked page) HERE. It's 6 pages of thread, but worth the time. Easily the best-informed and most informative discussion on the IMS issue I have read or heard, bar none.
#6
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Interesting... three designs? So, M97 is third design?
Now we need to move back in time. Here is a guess as to how the bearing ended up submerged. The engine was designed wet sump, the first Porsche boxer engine with that approach since the 912/356. When they started testing it in the prototype 996, they found the oil pick-up was sucking air instead of oil (with the new suspension and great tires under high lateral "G’s"). When sump baffling changes did not fix it, they added a couple liters of oil to the sump. Cheap fix, new dipstick. But, the bearing (which was designed dry) was now wet when not running. Well,….. someone had to sign off the engineering change forms, including the impact of the change assessment. Now we have a paper trail to the guilty. When the bearing problems started, the cover up began.
So, the guy who messed up ….either found a way to get it blamed on the least liked guy in the group (and is now the area manager), or…..he has long since left Stuggart, and made a career making weinerschnitzel in the Black Forest. You might laugh, but this happens all the time in big organizations. The case everybody remembers ……..is the space shuttle o-ring disaster.
When we do the math on the grease lubed (but not immersed) dual row bearing, it looks really good . Lots of load margin, and the combination of small OD and small ***** keeps the ball speed and centrifugal loads down. No problem at all grease lubed. The problems start when the grease is gone.
The second generation single row bearing is simply the dual row cut in half. It is really that basic. Same ID and OD, half the ball count. So the contact stresses are doubled. We now have a bearing that is far more likely to overheat and die. Based on the failures seen , this is exactly what is happening. These engines should have the hybrid ceramic upgrade done now, don't wait for the clutch to go.
You can’t admit you made a mistake and go backward , so……..you make a third design! You fix the contact stress by putting this big single row bearing in place. The load capacity math on this bearing looks fine, but the limiting speed is very questionable. The increased diameter makes a big jump in ball speed (speed varies as the square of the radius) because the OD of this bearing spins. The ***** are large and heavy, making high centrifugal force that wipes lube off the race. If you are driving around town, and rarely redline the engine, it is OK. Endurance running this design at sustained high rpm is asking for trouble. We have not completed the analysis on the impact of just changing the ***** to ceramic on this bearing. With the ceramic ball’s weight reduction, it will help the centrifugal issue quite a bit. (We do have a ceramic ball version of this big bearing on the road, but it is far to early to tell if the solution is adequate. All indications are it is an improvement, and we can custom make one of these for you if you really want it.) Question is, will it be enough. Since you have to tear the engine down to service this bearing, we are considering making the shaft go back to the (field service capable) dual row. It will require a very precise, cylindrically ground spacer sleeve to make it happen. We would have to do the upgrade in-house to control the fit. More work is needed on this one. Since every engine has to be torn down to fix this bearing, we don’t expect very many sales for a period of years.
So, all this probably happened because ……….no one wanted to tell the boss a $300 bearing was needed to fix it, or the business people could not make a case for spending the money.
So, the guy who messed up ….either found a way to get it blamed on the least liked guy in the group (and is now the area manager), or…..he has long since left Stuggart, and made a career making weinerschnitzel in the Black Forest. You might laugh, but this happens all the time in big organizations. The case everybody remembers ……..is the space shuttle o-ring disaster.
When we do the math on the grease lubed (but not immersed) dual row bearing, it looks really good . Lots of load margin, and the combination of small OD and small ***** keeps the ball speed and centrifugal loads down. No problem at all grease lubed. The problems start when the grease is gone.
The second generation single row bearing is simply the dual row cut in half. It is really that basic. Same ID and OD, half the ball count. So the contact stresses are doubled. We now have a bearing that is far more likely to overheat and die. Based on the failures seen , this is exactly what is happening. These engines should have the hybrid ceramic upgrade done now, don't wait for the clutch to go.
You can’t admit you made a mistake and go backward , so……..you make a third design! You fix the contact stress by putting this big single row bearing in place. The load capacity math on this bearing looks fine, but the limiting speed is very questionable. The increased diameter makes a big jump in ball speed (speed varies as the square of the radius) because the OD of this bearing spins. The ***** are large and heavy, making high centrifugal force that wipes lube off the race. If you are driving around town, and rarely redline the engine, it is OK. Endurance running this design at sustained high rpm is asking for trouble. We have not completed the analysis on the impact of just changing the ***** to ceramic on this bearing. With the ceramic ball’s weight reduction, it will help the centrifugal issue quite a bit. (We do have a ceramic ball version of this big bearing on the road, but it is far to early to tell if the solution is adequate. All indications are it is an improvement, and we can custom make one of these for you if you really want it.) Question is, will it be enough. Since you have to tear the engine down to service this bearing, we are considering making the shaft go back to the (field service capable) dual row. It will require a very precise, cylindrically ground spacer sleeve to make it happen. We would have to do the upgrade in-house to control the fit. More work is needed on this one. Since every engine has to be torn down to fix this bearing, we don’t expect very many sales for a period of years.
So, all this probably happened because ……….no one wanted to tell the boss a $300 bearing was needed to fix it, or the business people could not make a case for spending the money.
#7
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Practical reality so far proves single row design to be reported less than dual row failures.
It just keeps me thinking - to sell my car now for 40k means to add at least 30k cash for 997.2 s car. I guess i will take my chances
It just keeps me thinking - to sell my car now for 40k means to add at least 30k cash for 997.2 s car. I guess i will take my chances
Trending Topics
#8
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
One thing I took, is that IMS bearing are NOT designed to sit with engine off, for weeks/months at a time! Therefore, more of the problems are on cars that are NOT driven.
#9
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Clearly this is a point of the engine that is prone to failure, it's just anyone's guess at this point what percentage of cars it affects - and the best estimate given so far was the 10% in 90,000 mile figure by the retired bearing engineer. Whether that is classified as a guess or estimate requires more data.
#10
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
It wasn't Bill Ryan (CasperLabs) that said that. It was some member called Valley996. It's same number that's been floating around the internet with no real data to back it up. I don't think anyone really knows the real statistic. The following is what was posted:
Also, it's not the newest single row (MY06-08) design that seems to be worse than the older dual row design. He's talking about the single row design used for the MY02-05 cars. The LN Engineering site says the same thing, that even the failures with their LN bearing retrofit have been with this single row design found in the MY02-05 cars.
Also, it's not the newest single row (MY06-08) design that seems to be worse than the older dual row design. He's talking about the single row design used for the MY02-05 cars. The LN Engineering site says the same thing, that even the failures with their LN bearing retrofit have been with this single row design found in the MY02-05 cars.
Yes, he talked about a third design, which pertains to M97, and it looks like the IMS redesign in 996 was worse than earlier Boxsters?!
All in all, it really makes me wonder how NO ONE went for a class action lawsuit, or to force them to a recall, as problems started in Boxsters of the 90s! and basically Porsche never admitted to IMS wrong design in the earlier cars?!
#11
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
Agreed, also as much as post is informative, it is also advertising for people to purchase/upgrade their IMS on 996s, so they are highlighting the worst case scenarios.
One thing I took, is that IMS bearing are NOT designed to sit with engine off, for weeks/months at a time! Therefore, more of the problems are on cars that are NOT driven.
One thing I took, is that IMS bearing are NOT designed to sit with engine off, for weeks/months at a time! Therefore, more of the problems are on cars that are NOT driven.
The ***** are large and heavy, making high centrifugal force that wipes lube off the race. If you are driving around town, and rarely redline the engine, it is OK. Endurance running this design at sustained high rpm is asking for trouble.
#12
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
I do not think it is legally possible to render any design 'wrong'. You can only sue against certain business practices. There were lawsuits but none resulted with anything, I guess.
#13
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
The other point I found interesting was that Bill Ryan stated the following regarding the 3rd gen design of the IMS bearing for the MY06-08 cars:
The point here is that people who track their MY06-08 997s frequently might be more prone to an IMS bearing failure "if" Bill Ryan's theory is correct. This is the opposite of the popular drive it like you stole it theory, which still could hold true for the 996 cars and MY05.
The point here is that people who track their MY06-08 997s frequently might be more prone to an IMS bearing failure "if" Bill Ryan's theory is correct. This is the opposite of the popular drive it like you stole it theory, which still could hold true for the 996 cars and MY05.
#14
Rennlist Member
![Default](https://rennlist.com/forums/images/icons/icon1.gif)
BTW, since you got the old IMS design, why don't you upgrade anyways? Either to his or LN engineering?
#15
Rennlist Member