IMS settlement follow up

[Jake Raby]

Originally Posted by southernstar

In the latest engines, Porsche eliminated the IMS - no IMS, no IMS bearing to worry about.

Brad

Yeah. Lets see how that works out. We've been inside the 09 and later engines for over 3.5 years now.

A Porsche overhead cam engine has utilized an "IMS (aka layshaft) since the mid 1950s, beginning with the 547/1 and that was done for a reason.

[Perfectlap]

Originally Posted by Jake Raby

Yeah. Lets see how that works out. We've been inside the 09 and later engines for over 3.5 years now.

A Porsche overhead cam engine has utilized an "IMS (aka layshaft) since the mid 1950s, beginning with the 547/1 and that was done for a reason.

How is the bearing-free IMS Solution different from the bearing-free redesign in the 9A1 "solution"?

[Jake Raby]

Originally Posted by Perfectlap

How is the bearing-free IMS Solution different from the bearing-free redesign in the 9A1 "solution"?

The 9a1 engine drives the cams directly from the crankshaft. Pictures of the internals can be found on our facebook page under the album "4.2 DFI Beast". I am putting together a WTI Engine Mechanical Class for the 9a1 and that will be available in May of 2014. Along with it will come some better illustrations.

[Trey T]

Jake,

Yupper! Only time will tell w/ the IMS-less. However, simplicity in engineering is always the best ingredient for a successful product.

Southernstar is correct with his statement; there's no argument about that. If I understand your implication/statement correctly, then no body is questioning the decision that porsche made to use the IMS b/t the crank and cams but many people are questioning the use of the roller bearing on the IMS. When a highly sought after company changes the design of their engine drastically, deleting IMS, their confidence in previous engine design is questionable. I'm not saying it's a problem, but it's extremely questionable.

Prior to 1996 when the Boxster came out, what type of bearings did they use for the IMS?

Originally Posted by Jake Raby

Yeah. Lets see how that works out. We've been inside the 09 and later engines for over 3.5 years now.

A Porsche overhead cam engine has utilized an "IMS (aka layshaft) since the mid 1950s, beginning with the 547/1 and that was done for a reason.

[thom4782]

Oil starvation does not explain why the IMS failure rate of a sealed single row IMS bearing is 7 percentage points higher than its dual row counterpart rate of nearly 1%. The more likely reason is that single row bearings are weaker than dual row ones and, as such, they cannot carry IMS dynamic and thrust loads as well. This reason also explains why IMS bearings last longer in cars that run at higher RPMs - the drive it like you stole it ones. BTW: replacing the OEM bearing with a ceramic one fixes the loading problem.

Oil starvation also does not explain the roughly 1% failure rate common to all sealed IMS bearings. The most likely reason all IMS bearings suffer this baseline failure rate is leaking seals compromise lubrication by allowing oil to mix with grease. The resulting mixture provides much less lubrication to ball bearing and race surfaces than grease alone or oil alone. This reason also explains why IMS bearings last longer in cars that lessen the chance of seal degradation by changing oil often. BTW: installing an unsealed bearing or removing the seal on a currently installed bearings cures the compromised oil problem.

Oil starvation may explain potentially different failure rates in unsealed IMS bearing cars that use different methods of delivering oil to bearing assemblies. But first, it’s important to know if the failure rates of the two methods are actually different. The answer will come only when many unsealed IMS bearing cars with different of maintenance and driving histories amass a reasonably high number of service miles - say at least 50,000 on average. Until then, people must rely on seller opinions and the track records of their products. Both sellers claim their products are great. The LN Retrofit has a track record of almost no failures over several years. DOF is just beginning to build its track record.

So grab a few drinks and some popcorn and sit back and watch the debate as it unfolds over the next few years. Eventually, real world experiences will settle the relative failure rate question among the competing lubrication methods for unsealed IMS bearings.

[Perfectlap]

Originally Posted by thom4782

Oil starvation does not explain why the IMS failure rate of a sealed single row IMS bearing is 7 percentage points higher than its dual row counterpart rate of nearly 1%..

where are you getting this 1% and 7%?

[KRAM36]

Originally Posted by Perfectlap

where are you getting this 1% and 7%?

Check this chart he posted here.

Autoweek Words on IMS

[Perfectlap]

Originally Posted by KRAM36

Check this chart he posted here.

Autoweek Words on IMS

Those stats are for failures tracked by Porsche through their engine replacement program.
They leave out the mountain of cars Porsche had no dealing with with post warranty where owners were entirely on their own. There are far too many variables left out to put any weight behind the percentages in the Porsche numbers beyond that single bearing cars fail far more often than dual row. Its pure guessing to attempt to decipher the technical cause based on the imprecise degree of separation. For instance a dual row bearing car may catch up to a single row bearing car in terms of probability of failure if given enough time or mileage without addressing the bearing. I can not think of a more difficult statistical probability to pin down due to the infinite number of underlying variables. Its like parachute jumping over Normandy in WWII.

[thom4782]

OK, think of the 1% and 8% as lower bounds on actual rates across all cars.

It doesn't change my points. They address the situation where the IMS bearing fails first, which leads to subsequent damage of other engine parts.

I do recognize, however, there are a number of failure modes where another part fails first, such as a chain rail breaking, that subsequently leads to the IMS bearing destroying itself as a consequence.

[kashmir]

Originally Posted by Perfectlap

Those stats are for failures tracked by Porsche through their engine replacement program.
There are far too many variables left out to put an For instance a dual row bearing car may catch up to a single row bearing car in terms of probability of failure if given enough time or mileage without addressing the bearing.

This is true , the bigger duel row has more bearing to wear away before failure, it takes longer and with more bearing material being circulated throughout the entire engine there is more secondary engine damage.

[thom4782]

Originally Posted by Perfectlap

Those stats are for failures tracked by Porsche through their engine replacement program. They leave out the mountain of cars Porsche had no dealing with with post warranty where owners were entirely on their own. There are far too many variables left out to put any weight behind the percentages in the Porsche numbers beyond that single bearing cars fail far more often than dual row. Its pure guessing to attempt to decipher the technical cause based on the imprecise degree of separation. WWII.

I disagree with your comments that one can't "put any weight behind the percentages" and "it's pure guessing" tu use the Porsche numbers because statistics show that the uncertainties between Porsche reported failure rates and actual ones are likely very small to make meaningful differences.

For example, if Porsche used just one-fourth of all actual dual row failures when calculating its reported rate, which is very likely the case, then one can say with 95% certainty that the actual failure rate for all dual row cars lies somewhere between 0.9% and 1.1%.

Moreover, if Porsche used just one-sixth of all actual single row failures when calculating its rate, which is even more likely the case, one can say with 95% confidence that the actual rate of single row failures lies somewhere between 7.6% and 8.4%.

These differences - 1% versus 0.9% to 1.1% and 8% versus 7.6% to 8.4% - are just too small to disregard the reported Porsche numbers.

[kashmir]

Originally Posted by Trey T

Prior to 1996 when the Boxster came out, what type of bearings did they use for the IMS?

On air cooled 911 it is a lapped bearing with an insert to support the rear journal.

[Trey T]

Do you know why they change it to roller bearing? is it because of assembly issue?

Originally Posted by kashmir

On air cooled 911 it is a lapped bearing with an insert to support the rear journal.

[kashmir]

Originally Posted by Trey T

Do you know why they change it to roller bearing? is it because of assembly issue?

The other side of the IMS shaft has the lapped bearing and the 8mm key that drives the oil pump, so there is plenty of lubrication on that side of the engine. It does cost money to cast into the block the oil passages. Plus it is easy to the drive cage bearing into the block on the flywheel side so you have speed of assembly. The original duel row bearing is only use by Porsche, to save more cost after they thought it was safe to build cars that way, they started to use an over the counter single row bearing that is also used in a GM alternator I believe and that is when things started to go "Tic Tic Boom!!''

[thom4782]

The total failure rates - dual 1% and single 8% - were provided during the discovery process of the IMS class action lawsuit. The 7% is the incremental difference between to two.

[Trey T]

I see. Thanks.

Originally Posted by kashmir

The other side of the IMS shaft has the lapped bearing and the 8mm key that drives the oil pump, so there is plenty of lubrication on that side of the engine. It does cost money to cast into the block the oil passages. Plus it is easy to the drive cage bearing into the block on the flywheel side so you have speed of assembly. The original duel row bearing is only use by Porsche, to save more cost after they thought it was safe to build cars that way, they started to use an over the counter single row bearing that is also used in a GM alternator I believe and that is when things started to go "Tic Tic Boom!!''