There have been a lot of possible theories mentioned in this respect; low miles, lack of aggressive driving, running the engine at 3,200 to 3,400 RPM for prolonged periods, and so on. I'm not sure how pertinent any of these ideas really are, or how much data is available to support them.

As a technician, you learn not to place a lot of credibility in unconfirmed operating parameters, and to focus on identifiable or confirmable commonalities in failures, such as the difference in failure rates between the single and dual row units, or off center case openings, which were also a major issue in the early RMS failures on the M96.

From experience, there is more than one factor involved in the IMS failures. There has always been the possibility that some of the OEM IMS bearings simply were not good. When one fails catastrophicly, there is little left to analyze, so that has never been confirmed to my knowlege. Off center IMS shafts are real, once removed from the engine they can be tested for this, and some rebuilders even "stockpile" good ones for future customers. But without a method to test them while they are still in the cases it prevents you from knowing if a shaft is good or bad. And if you think about it, a shaft that is not turning true, and is at least partially loaded down with oil that has leaked past the IMS is constantly beating the Hell out of the bearing, regardless of whatever else is going on. Problems with off center or non concentric case openings such as the RMS where identified as an issue by Porsche several years ago when they released a "go/no go" tool to test the RMS opening; and if the case failed, the engine was replaced as there was no realistic way to repair it. It does not take a rocket scientist to realize that the IMS flange opening is just a couple of inches below the RMS opening, and looks exactly like the RMS opening, only smaller; so if one is wrong, the other one could be as well. Everyone here has probably read about chain wear pads failing in these engine, so what factor does slowly developing "whip" in the long chains connecting the IMS shaft to the cams play? Again, data is thin and sketchy.

Only someone like Jake, who spends most of his life staring at the internals of a large number of these engines is really in possession of most, if not all of the facts. And unfortunately, both as the direct result of people copying what he has spent years developing, and the grief he has incurred on websites, he has pretty much stopped saying a lot, or charging for access to that knowledge.

I really think the moral of this thread is....

"Sometimes s**t happens"

More like, "Sometimes there just isn't a simple answer.........."

One last thing...
 

...and then I'm done. Really.

I own a 1990 Mazda Miata, a very early build. My car is one that has what the Miata community calls a "Short Nose Crank", google it.

All of these cars are supposed to be ticking time bombs, with crank shafts that WILL snap at any moment. If you read the forums, you shouldn't even think about adding an aftermarket turbo to one of these.

My car has 285,578 miles on her, and she has been running 12 pounds of turbo boost since she had about 50,000 miles on her. She has a Flyin' Miata aftermarket turbo kit on her.

We've driven this car all over the country with zero drama.

Every time a fellow enthusiast sees my car and strikes up a conversation, the "short nose crank" issue comes up and every time, they are shocked that my car hasn't given me any trouble.

So now I go out and buy one of these "time bomb" Boxsters. With the Boxster, I didn't temp fate. I replaced the IMS immediately upon purchase.

So, I've been the guy who "doesn't worry, be happy and drive" and I've been the paranoid freak who immediately dropped big money on preventive maintenance.

Choose your poison.

But wasting time on the "why" of it, just seems like a waste of time.

I could list a dozen different cars that have some percentage of catastrophic failures.

You can't mass produce machines this complex, and sell them to people all around the world, without some of them blowing up at some point.

Now I'm done.

:cheers:

There is only two things that can horribly go wrong in a high speed or heavy shaft/bearing design really. First is (as you've indicated) the TIR or runout, or both for this matter. Second is rotational torque vibration & noise caused by improper damping (as you've also indicated, the chainS, and which I also personally suspect; critical speeds). Lubrication is also a failure type however in a shaft application rotating >5000RPM the first two are far more subject to cause catastrophic failures way-long before, lubrication or not.

The good news is the two main issues above are easily detectable using modern vibro acoustic technologies. My advice for the key players in the IMS business would be to develop a tool that is capable of sensing and therefore take actions based on acquired data from healthy and failing engines. Same techniques used in the aerospace and other transport/military industries, whose those actually are 'real-time'. Basically "staring at the internals" in engineering terms.

You said "there is little left to analyze". You are getting this wrong, this needs to be carried out before the failure thus 'preventing it'. Its called predictive maintenance AKA "Solution".

Sending ppl out of fear to change their perfectly fine bearings to me sounds a bit primitive given the vast and widely available condition monitoring kits (high end sensors) and training offered commercially these days e.g. Mobius, Siemens, I pass so many others.

Some who aren't familiar with VA technology will tell you a miniature car engine is a noisy environment (LOLOL), by all means, please ignore these twats; the tech is used in both turbofan & turbojet engines and +50 tons machinery motors/shafts (e.g. ships, energy/nuclear facilities, etc).

Time to modernize a tad guys (if you really care about these Porsche cars anyway).

my 0.2

Some time back, an engineer with a background in vibration analysis tried to deploy what appeared to be a very sophisticated technique and equipment to do exactly that. Unfortunately, his efforts went no where due primarily to interference vibration signals from other sources in the engine. Google it, it has already been tried and discarded.

As for "sending people out of fear" to do anything, well that is more of an opinion than a fact. If I never installed another retrofit kit in one of these engines, it would not denigrate my business or income one iota. When people ask questions, we simply try to offer the best information as we know it; what they do with that information, or how they internalize it, is strictly their business. The simple facts are that while a large number of owners of M96/97 engines will never have a problem, others will not be so lucky. The percentage failure rates are documented and in the public domain. If you choose to take preventative action, alternatives are available. If you choose not to, that is your business. No one is hard selling anything.

We use VA in all sorts of industrial electrical motor driven rotating equipment but I've not seen it used in IC engines. There are a number of reasons why not. Perhaps a prox probe on the shaft would work if somebody could figure out how to install one. I'm sure smarter people than me are on it. :) As far as predictive technology goes there is of course oil analysis and the IMS Guardian (is it still available?) although I can't say how well that works. I may end up using oil sampling and filter inspections myself. It can be done cheaply.

Excellent point. It is part of the cost of ownership. I bought mine 3 years ago and have made several great trips including the Black Hills in 2015 and B.C. in 2016. These cars are worth keeping them running properly and addressing any issues because they are a blast to drive.

IC engine, rotary machinery, source doesn't matter or perhaps VA is misunderstood here. Aquisition would come from the horizontal, vertical and axial planes near the shaft/bearing (not from an object particularly e.g IC engine). Vibrations are 'freq' (in words) and can easily be filtered out if somehow seen as 'interference' by your equipment/engineer. In fact the more you have the better really. Seriously I'd just call your local Siemens rep and get them to help as one of their Eng Dept is doing this all day long (yes, on cars too, google it). They offer completely free training shall you decide to use their technologies (as in, you could do it yourself afterward bud).

Please Try, what can you loose.

Predictive: That is exactly what I am talking about and I don't see why not this guardian thing wouldn't work (if I've understood its concept correctly). Actually a brilliant idea and I couldn't recommend it more. Certainly a better technique than just wacking out perfectly fine bearings.

OT. Can someone let me know why my Porsche dealer categorically refuses (even if I pay) to periodically replace my bearing? They strongly recommend me NOT to do it. Would it be because it'd be seen an acknowledgement to the class action in a way? Are your P dealers fine with it in the USA?

Don't believe me? just call the dealership here in Shanghai (although this was back in 2008/09)

https://www.plm.automation.siemens.c...023-220992.jpg

5800 Granite Parkway
Suite 600
Plano TX USA 75024
(v) +1 800 498 5351

What can I lose? Simple: time and money. Multiple fixes already exist for the problem, and I am not in the business of re-engineering Porsche's problems. As previously mentioned, and experienced engineer in this field could not make it work, even with help from a university.

Porsche very quietly released a memo to their dealer network years ago stating that in their "official" opinion, it was not possible to replace the IMS bearing without taking the engine apart. This gave the dealers an out, both not to get involved in retrofits, and to void warranties on engines that had one done. So while some dealers actually sent techs to Jake's IMS class and quietly did do retrofits, most dealers stayed with the factory line" It cannot be done."

Another point is Porsche's parts network; they only sell complete replacement IMS shafts with the bearing already in them, they have never offered the bearing as a separate part.

Here is a link to the start of the IMS vibration study, which ultimately went no where (take note of where it was posted): Good Vibrations Technical Article by Pedro

Time & money: I'd rather spend this on cocaine and prostitutes, well, if I had any of that time OR money to spend at the first place anyway ;)

I c, thanks for the explanation. Sux they don't really. I was forced yo learn how to live and enjoy with the risk

I won't click on this link Jeff, please contact someone NOT currently affiliated with the IMS business bud.

Good guys in Texas I heard (its free to ask and take 20min of your time btw)

Interesting R&D project. There are lots of hurdles before that service would be widely available which explains why it went nowhere. Or, you can change your bearing on a preventative basis, do a little oil analysis perhaps and call it a day. (or do nothing as some have suggested) Now, if only I could find a decent Boxster around here. ;)

When this individual was shopping around his vibrational analysis techniques, the individual that runs that website latched onto him, probably figuring that he would coattail his success onto that of the technique and be ahead of everyone else in the retrofit business. Unfortunately, it did not work out for either of them as they never identified the specific signals from an IMS starting to go south.

The person behind the concept actually posted on several Porsche related websites, including this one if memory serves.

Back in the day (early 1912), I was in touch with Mark Jennings (the industrial engineer specializing in vibration studies). In fact I introduced him to the BRBS folks because he was looking for a wider sample of cars so he could start building a data base that he might develop into a predictive method of detection. In between that time and BRBS, I think his local to him experiments led him to the conclusion that what worked in an industrial fixed site environment wasn't going to work for a car mounted engine and he abandoned the quest and that may well have been because of economic reasons. A manufacturing plant might spend $10k to do a replacement based on a 75% probability of the detection method just because the failure could have multi-million dollar impact on their production and they would do it during normal plant shutdown. But how many shop owners would install a costly tool that was only that accurate and who would advocate replacement on the maybe it is bad basis.

There was an article in one of his local INWR PCA newsletters.

Thanks for the intro and sharing this with us Mike. Interesting.

Ok, I did clicked that link out of curiosity and the main problem I'm seeing is "Mark uses a portable, digital vibration analyzer"..

I was raising this here because I know that the key players in the IMS business are reading this and DOES actually have the dosh required to R&D this for the community. Yes, its all about funds/investment. But once you have the tool then imagine for a minute.

To what end? The major "players" in the IMS retrofit business apparently feel that they have found a fix for the issue, and with some 30K successful retrofits by the largest, the numbers seem to back up that position. With the IMS now engineered out of Porsche engines, and the total population of non retrofitted cars with IMS bearings diminishing every day, exactly why would they embark on a costly R&D project that has less of a chance of paying their investment back with every passing day? They are a business, not a philanthropic organization working to help expand the knowledge base of the industry.