MadIrish

The failure rate of these cars in the dual row bearing was 1% and the failure rate of the single row AT THE TIME OF THE CLASS ACTION was 8-10% (it was to this larger cadre of failures I was referring). Since that time, nobody is recording how many additional IMS bearings have failed. Nor are they recording how many REPLACEMENT bearings or engines have failed (I'm not talking about aftermarket replacement bearings...I'm talking single row or large captive IMS engine replacements from Porsche). Further, Porsche would not reimburse anyone with over 100k miles or 10 yrs on it at the time of damage...meaning their own confidence in the survival of bearings past that time was also low. You really have no factual basis to assume 8% failure rate at 85k miles assumption 6 years or so after the data was presented in the litigation. You talk about miles driven on a fleet of cars and if the driving habits of all of those drivers was the same, maybe there'd be more validity...but

docmirror

Glad to hear you're an A&P. We need some of that here.

Now, having said that, there are some pretty sharp folk who've engineered a good solution. Sadly, the price they charge for the fix-up is pretty high. I"m an amateur in this specific failure mode, but if you can do something less expensive, the proof will be about +200K miles of satisfactory run-in. Some issues you're going to have to confront: Previous less costly fixes have tanked seriously. For various reasons. The exact failure mode(s) are not well defined. I've seen a bunch of theories, and some actual measurements. So far I know we've had serious NRRO with some shafts. There has also been evidence of normalized run-out. There have been issues with foreign contamination of the bearing. With acid etching of the ball or race. Rust/oxidation. Axial skidding, chain woggle, and even cases of unknown seizure of the outer race.

I'm afraid that the true solution would address all these potential failure modes. Which would be to disassemble and mic the shaft, balance, and then do all the needed bearing load and lube design. It seems like there is not going to be a 'quick/cheap fix'. But - I will encourage you to work up anything. More eyes on the issue is always good. Unless you know starting with a good shaft, true gear teeth, correct chain, no contamination, just solving the bearing problem may lead to unpredictable results. A few things we do know. The problem seems to be more common on under-utilized low mileage cars. Single row bearings are more failure prone(I don't know the percent). Note also the intermediate shaft is a non-flow through unit. Having an open cage bearing with full flow of oil onto the cage is a solution, but the shaft needs to be drained as well. A certain amount of drainage back through the ball cage will happen, but I don't know how much outflow is enough for the spray into the bearing.

Good luck, keep us posted.

rocketbob

Thanks for pointing out this solution as I was not aware of it. If I were not so set in my DIY ways I would likely go with their solution since it uses pressure fed roller bearings. SKF has some bearing calculators online to determine the expected life of a bearing based on type of lubrication and contamination factors. It would be interesting to compare the two (roller vs. ball) to see which one in theory would have more life given expected contamination values one would see with normal engine oil contamination.

Thank you. I have an IA (inspection authorization) from the FAA so I have a bit of a keen eye for doing modifications in the airplane world. I've had to deal with analyzing ball bearing failures in some Lycoming engines that have a ball bearing support for magnetos so I'm aware of how they fail in bathed applications. In that case the bearings are fed with splash oil and I believe underutilization is a contributing problem. Water and acid gasses are byproducts of combustion which end up in the oil. If the engines sit for long periods of time then these contaminates cause corrosion on steel parts which is obviously hard on contact bearings.


Sure, just don't know the extent of damage yet, if any. Will get the car up on the lift this weekend and start poking around. Dropping the motor and transmission is something I was planning on doing anyway to do the IMS bearing fix. I know I don't have to do that but I want to do some other maintenance as well and its just easier if everything's out in the open.

charlieaf92

I see a lot of discussion about roller and ball bearings. Just for the record, you've seen this right? http://theimssolution.com/

docmirror

Quite possibly related failure modes. Many of the failed cars have low mileage. If think right, the DOF uses a passage through the IMS shaft from the pump on the rear of the engine. The issue with this is the oil they are supplying is neither filtered, nor cooled. It's right from the pump. Not a best-case method, but it's something. To do it right, the IMS bearing should come out anyway to remove the inner plastic seal, for flow through. I don't know if they do this, but extraction of the bearing renders it unusable.

Now, I will deny ever writing this(haha) but I have heard - through various grapevines that if the car has a full-flow oil filter, and the failure is caught soon enough through short oil exchange cycles, and careful pleat inspection that an IMS bearing failure in its early stages is not catastrophic. This also is supported by people who have installed a 'chips' detector light in the sump, and stopped at the first indication of metal in the juice. (My most exciting flight was near Ft Lewis in an AH-1L when the chips light came on. I auto-ed into a bean field and they came and got it with a big truck and trailer)

Russ21

Porsche reimbursed on cars upto 130k miles
your not talking sense, nore with facts.
have you abetter formula for working it out!!
if not please dont reply

Slakker

Is this how you would talk to someone face to face? In front of your kids? Please take a step back and ask yourself is this a positive addition to forum or am I being a bit toxic? You've obviously read the lawsuit which is more than 98% of us. And I applaud that. But beating people over the head with it provides benefit to no one, not even yourself.

Russ21

85,000x 100 = 8,500,000 / 0.008 = 1,062,500 ( don't make the classic mistake of 85,000 x 100 = 8,500,000 x 0.08 = 680,000) as this is 8% of the mileage not 8% of cars, but it is a very easy mistake.
Regards Russell

Russ21

All I've done is work out a simple equation for people who ask a specific question regarding IMSB F. so people aren't frightened, as I once was regarding imsb thinking my first porsche was going to explode.
So now people can see how likely it is in the real world.
Some people doubt my equation and call me stupid or they try to dismiss it without a better scenario,
so when they question it I reply.
If it's questioned constructively I will give a constructive reply.
But if people criticise my spelling on a forum when they can't spell well what can I say.

I have had 1 other constructive criticism but his maths was incorrect, but I was extremely polite and explained his error without sarcasm.
If you or anyone comes up with a better equation I will back it, but you lot don't give me a hard time for helping people.

Regards
Russ

il pirata

Russ21 you have a PM.

MadIrish

Oh, man, Russ, you got me....I made a typo...I feel so humbled and ashamed. Yes, I read the settlement, too...it was 130k miles.


Regardless, you are calculating an incorrect Mean Time Between Failure because you don't know how many miles each of the failed 8 cars in your insurance study (that you referenced elsewhere) traveled before failing. In addition the 100 vehicles/8,500,000 miles driven is not a large enough sample for a good FIT/MTBF calc...more like 1,000,000,000 miles would be a better sample. Nor do I think 85k miles in that survey really expresses the useful life period of the automobile, a 25k to 200K mile survey would be more in the belly of the "bathtub curve", where infant mortality failures and wear out failures are excluded.

Anyway, I see what you are trying to do, but, again, I believe the assumptions are wrong. No attack, no reason to get your back up. Truth is, neither you nor I can calculate a true failure rate because we simply do not have the data required.

Flat6 Innovations

Several of the novel concepts you have mentioned are covered by Mr. Raby's Patents 8,992,089, 9,687,974 and 9,687,974. The Spin On filter adaptor providing an oil outlet was just granted US Patent 9,909,469 and this issues on 6 March 2018. You may want to research these documents before moving forward.

Russ21

your correct 100! so I used a %, 1% = 100% / 100 of known vehicles that failed at the time of legal action, so the reason I used 100 cars, is so its an accurate % for people to understand, I think everyone grasped this bar you.
So 100 cars is a representative of all the cars. DO YOU UNDERSTAND.
I'm really sorry you don't understand but I can't teach you maths I just don't have the time.
But I can tell you every time you answer the credibility you had goes down a few % :-)

MadIrish

LOL. I don't need you to teach me maths, Professor....I've studied probability and statistics and have a passing familiarity with failure analysis.

In another thread, you made the claim that your 8 failures in 100 car of 85k miles each was based on a study you saw by 1 insurance company, not by the overall figures in the settlement. Then you said 8% over the life of the car. Now you are saying you are merely simplifying the example to make it easy for the unwashed masses to understand based on the data from the class action. . Which is it? You also suggested that you can average the failure rates between the 2 classes of cars (dual row models and single row models) to 4%, which you cannot. You must look at them as discrete cases as they are completely different designs and in any engineering study would be analysed separately. .

You are presenting this 1,062,000 miles as a mean time between failure.
.
If you are relying on the insurance company analysis, then the data set is not big enough to do so, nor is it complete enough (ie no detail on when cars failed). If you are basing it on the class action lawsuit, the data is not complete (again, no data on when the cars failed) and does not cover the usable life of the car. To understand MTBF, you need to understand the up time of each car in the dataset....and none of these datasets provide that. These are facts that render your analysis inaccurate. That is all I am saying. . A failure every 1,062,000 miles, or whatever you suggested, is an optimistic view. Do i believe it falls to a MTBF of 100k miles if we had the correct data, NO.. I simply started out questioning your assumptions and you continue with your arrogant silliness..

Truth is, if I had a dual row, I'd leave it alone, myself. If I had a factory single row....I'd change that thing. I have a dual row with a replacement IMS (not The Solution) purchased by the PO, so I will be faced with a decision in a few years as the suggested maintenance interval is reached.

TonyTwoBags

Ditto. I haven't seen much in the way of dual rows failing, just lots of intermix & scoring.