Yet another IMS "solution"

[jaykay]

Originally Posted by schoir

Since it is widely accepted that lack of lubrication is the main cause of IMS bearing failure, providing a solution which provides adequate lubrication should solve the problem. Then there is no need to unnecessarily be alarmist about pistons and valves banging into each other.

The above also ignores the additional unknowns that may be introduced by a new design with new parts. All of those parts add a level of complication which is simply not necessary to solve the problem, namely lack of lubrication.

Finally, from my limited understanding of bearings I know that journal bearings don't fare as well as roller element bearings (ball bearings) at the time when most engine wear occurs...at initial startup.

If there are any bearing engineers amongst our members, perhaps they could edify us further.

More time and more real world testing will provide the answer to the question of which approach solves the only problem that we should be considering... lack of lubrication.

In practical terms, I'm not so much interested in the "art", but more in the result. "Art for art's sake" is a good motto for MGM, but not for bearings. This would not be the first time that a less expensive, simpler solution proves to be the best solution.

Regards, Maurice.

There are many different bearing designs. They each have their advantages and disadvantages. A hydrostatic (oil pressure fed) plain bearing is hard to beat in that the wear surfaces rise off each other and run on a film of oil. This is dependent upon bearing wear surfaces fits, tolerances, and geometrics along with lubricant pressure, flow, film strength, viscosity etc. The trick is to get appropriate oil flow to this location.

Rolling element bearings will have point load contact areas and won't be hydraulically supported to the degree of the hydrostatic plain bearing. You will have more time with metal on metal or ceramic. Without suitable oil feed a hybrid rolling element bearing is your best option. Theoretical cylindrical rolling elements would be a logical choice but they are not yet readily available and harder to make. They will also suffer if there is a thrust load component. Ceramic rolling element balls are now very common and are the standard in poor lubrication environments. Even prior to cermics ball rollers seemed to be favoured in bad conditions even though their load capacity was lower than cylinders; this is something I have found not always to be the case.

One just has to look at the other end of the IMS shaft for proof of concept. If there is suitable oil flow available then the hydrostatic plain bearing will the best option in this case

[jaykay]

Oh just wondering if there's a new product in the works for 2005+ engines where the the outer seal is removed and then and then hit with an oil feed....A Cayman owner friend of mine would want to know.....not for me

I am riding on a ceramic dual row from a while back

[schoir]

Originally Posted by jaykay

Oh just wondering if there's a new product in the works for 2005+ engines where the the outer seal is removed and then and then hit with an oil feed....A Cayman owner friend of mine would want to know.....not for me

I am riding on a ceramic dual row from a while back

The first post in this thread is about exactly that:

Direct Oil Injection for IMS Bearings | TuneRS Motorsports – Porsche performance, repair and restoration

Regards, Maurice.

[thom4782]

Let me add several thoughts to the discussion...these are my opinions based on my reading the wealth of IMSB discussions in this forum and on others. I am not a parts developer nor am I an automotive engineer.

JFP described the nature of the IMSB problem well in post #26 in the following thread: http://986forum.com/forums/general-discussions/43117-excellence-say-just-remove-ims-outer-seal.html. When the seal on the stock bearing leaks, it allows a small amount of oil into the bearing area that mixes with the grease. The oil flow into and out of the bearing area isn't sufficient to completely wash out the grease and provide lubrication and cooling to the ball bearings. When this happens, the bearings degrade and the IMSB fails. As such, removing the seal and cleaning out the grease improves the longevity of the IMSB because the splashing of oil provides enough oil to the bearing surfaces to lubricate and cool them.

The direct oil injection part that started this thread recognizes this phenomena and it does two things: it requires removal of the seal and it feeds oil directly onto the bearings. It's advantage seems to be that it puts more oil onto the bearing than provided by splash oil. How much of an advantage is unclear to me.

The LN Retrofit is an unsealed ceramic bearing. It's extended longevity over the stock bearing comes from the fact that it is splash oil lubricated and uses ceramic balls. And as others have said, the ceramics last far longer than the stock bearing.

The IMS Solution is lubricated by pressure fed oil and it eliminates the ball bearings entirely. Its big advantage at least to me is that it eliminates catostrophic engine damage if the bearing should fail.

If I had to guess which combination of product offers the best protection, my ranking from most to least is:

1. IMS Solution
2. Direct Oil Injection with LN Retrofit installed
3. To close for me to call: Direct Oil Injection with unsealed stock bearing versus LN Retrofit alone
4. Unsealed stock bearing alone
5. Sealed stock bearing

What do others think? Does my explaination make sense. If I'm wrong, please weigh in so others have the best information available to them as they try to address their IMSB concerns.

[Stefan (Boston)]

I agree with most of your summary, thom4782.

My primary issue with "The IMS solution" is that replacing the ball bearing with a plain bearing may have unintended side-effects. The bearing type has an impact on the system. For example, a plain bearing is less efficient, which means that there is consistently more load on cam chains and the IMS teeth. I don't claim to fully understand the physics but I do know that unnecessary changes are a bad idea by definition.

In cases where the stock bearing is properly lubricated it has been shown to last over 200k miles with no significant wear. Since the chances of failure in a pressure-lubricated ball bearing setup go down to virtually nil, the risk of causing other problems by changing the bearing design suddenly outweighs the possible benefits.

Idling a car for a long time is an interesting but it is not a true test of the known-failure conditions. For example, it is known that unlubricated startup is one of the most stressful times for a bearing (and double that concern for a plain bearing). There is no reason to believe that temperature was a significant precipitating factor in the bearing failure. In the very worst cases, it took at least 30k miles of varied driving and multiple starts for the bearing to fail.

I suspect that we will find out what the new failure modes of "The IMS Solution" are in a few years when the first ones start to fail.

If you want peace of mind, choose a solution that is extremely reliable (oil-fed bearing) over one that is more likely to fail ("The IMS Solution"). In the absolute best possible failure scenario for "The IMS Solution", it is still thousands of dollars to repair. In the worst, it's still replace the engine time.

[kashmir]

Originally Posted by jaykay

most engine wear occurs...at initial startup

Here is a Master Lube engine pre-oiler. It is used on vehicles to pre-oil your engine before starting so as to prevent "dry starts".

[Jake Raby]

One just has to look at the other end of the IMS shaft for proof of concept. If there is suitable oil flow available then the hydrostatic plain bearing will the best option in this case

It took months for someone to say that... And guess where we took part of the design characteristics from?

We've NEVER seen the plain bearing end of the IMS wear... Never.