IMS solution,or Pedro's DOF

[Javi Cooper]

Originally Posted by Homeoboxter

It’s actually the opposite, since the bearing wear is twice as fast in the single row because of the double load compared to the dual row. So the single row starts pitting much sooner. DOF would make sense if the failure was the result of lack of lubrication. But that’s not the case in a bearing that’s swimming in oil all the time.

But that's actually the reasoning behind the DOF; the bearing, even though it's submerged in oil at rest, is NOT submerged in oil at all when the engine is running, contrary to popular belief. Here's a visual explanation from Pedro:

https://www.youtube.com/watch?v=qj06dqBk0to

[SC-986]

Certainly not an expert here and all I can offer is my own personal experience. I purchased my ‘04 S about 1 1/2 years ago. One of the selling points was that the IMSB was upgraded in 2014 at 87,000 miles. The car now has 114,000 miles on the odometer. The DOF option was used and at the time of purchase I hadn’t researched the major differences between the DOF and LN’s offerings.

Fast forward to today and my ‘02 base at 168,000 mi. recently threw a cam deviation code. It is in the shop for further diagnosis and so I have spent a good bit of time researching the different IMSB upgrade options in the event that is the problem.

It seems the naysayers of the DOF system claim that where the oil is drawn from the engine to lubricate the IMSB is problematic in that it could be contaminated with debris or cause oil pressure problems on bank 2.

To date with nearly 30,000 mi. on the DOF system I have not experienced any oil pressure issues and I drive it pretty hard through the twisties of the Blue Ridge Mtns.
The drain plug magnet and filter do not have any ferrous material on or in them.

Most people will not write about a thing if it is working as designed, they only write about it when it fails. In my research I ran across (3) occurrences where LN’s ceramic retrofit bearing failed between 30,000 - 40,000 miles resulting in catastrophic engine failure. I found (1) occurrence of a DOF system concern where there was some valve train noise on bank 2 and when the oil feed was disconnected the noise went away - no failures per se.

On my ‘02 base if it requires an IMSB replacement, because of the high mileage, I will probably go with the DOF option. The IMS Solution is the gold standard and if the car had lower mileage I would opt for that. With the DOF system I can take the 1000.00 saved over the Solution and apply it to future engine repairs.

[Homeoboxter]

Originally Posted by Javi Cooper

But that's actually the reasoning behind the DOF; the bearing, even though it's submerged in oil at rest, is NOT submerged in oil at all when the engine is running, contrary to popular belief. Here's a visual explanation from Pedro:

https://www.youtube.com/watch?v=qj06dqBk0to

Yeah, I came across this video. Still, I don`t think it justifies the need for DOF. The IMS is submerged almost all the way to the top of the shaft when your level is at the max sign, and is submerged around half way up when it`s at the min level. So, the inner ring (that is fixed) is always submerged in oil that will carry excessive amount of oil onto the balls and the outer ring. Centrifugal force has nothing to do with this because the inner ring is not spinning. Ball bearings do not require DOF. There are motorcycle engines with ball bearings operating at much higher rpm and temperature that an IMSB and they are totally fine with submerged or splashed oil lubrication or even oil mist in 2-stroke engines. But you don`t have to go that far, look at the ball bearings in your transmission, they are lubricated by splashing oil, and they don`t fall apart, even if the input shaft is spinning at much higher rpm than the IMSB.

[SC-986]

Originally Posted by Homeoboxter

Yeah, I came across this video. Still, I don`t think it justifies the need for DOF. The IMS is submerged almost all the way to the top of the shaft when your level is at the max sign, and is submerged around half way up when it`s at the min level. So, the inner ring (that is fixed) is always submerged in oil that will carry excessive amount of oil onto the balls and the outer ring. Centrifugal force has nothing to do with this because the inner ring is not spinning. Ball bearings do not require DOF.

If this premise is correct then why did the Porsche engineers specify a sealed grease filled bearing and not a bearing with the outer seal removed?

[Homeoboxter]

Originally Posted by SC-986

If this premise is correct then why did the Porsche engineers specify a sealed grease filled bearing and not a bearing with the outer seal removed?

No clue. The idea of a grease-filled bearing would not be entirely wrong if the shaft wasn`t sealed. Since it`s sealed, the pressure that builds up inside the tube in normal operating temperature forces the grease out of the bearing. When cooling down the opposite happens, vacuum in the tube results in seeping oil into the bearing. Eventually the grease gets replaced by engine oil, that`s what we see when we open a genuine bearing. I think if the IMS was depressurized this wouldn`t happen. Not sure though which is better...

[elgyqc]

Originally Posted by Homeoboxter

No clue. The idea of a grease-filled bearing would not be entirely wrong if the shaft wasn`t sealed. Since it`s sealed, the pressure that builds up inside the tube in normal operating temperature forces the grease out of the bearing. When cooling down the opposite happens, vacuum in the tube results in seeping oil into the bearing. Eventually the grease gets replaced by engine oil, that`s what we see when we open a genuine bearing. I think if the IMS was depressurized this wouldn`t happen. Not sure though which is better...

My understanding is that the advantage of the original sealed bearing is that misc. metal shavings in the oil (the stuff we see in cut open oil filters) does not get into the bearings and that the original grease is a better lubricant. As mentioned the pressure changes, with time, wash the grease out and the seals prevent an adequate supply of new clean oil. So if you remove the outer seal on an original bearing (or a replacement for that matter) the bearing will be well lubricated by oil, but it could be affected by metal bits circulating in the oil. But than again if there is enough metal in the oil to affect the bearing you likely have another serious problem. Just my $.02 worth.

[Homeoboxter]

Originally Posted by elgyqc

My understanding is that the advantage of the original sealed bearing is that misc. metal shavings in the oil (the stuff we see in cut open oil filters) does not get into the bearings and that the original grease is a better lubricant. As mentioned the pressure changes, with time, wash the grease out and the seals prevent an adequate supply of new clean oil. So if you remove the outer seal on an original bearing (or a replacement for that matter) the bearing will be well lubricated by oil, but it could be affected by metal bits circulating in the oil. But than again if there is enough metal in the oil to affect the bearing you likely have another serious problem. Just my $.02 worth.

I`ve heard this theory but it does not make much sense to me. In a normally functioning engine there`s no metal bits circulating in the engine. Debris is constantly being filtered out of the oil by the oil filter. If metal particles get to the oil there`s an engine faiilure coming soon anyway and a sealed bearing won`t make a difference. Larger particles, typically broken timing chain rail pieces that can`t go through the oil pick up mesh are too large to get to the IMS because there`s no space.

[kk2002s]

Running out of pop corn, hit the pause button even though I have seen this scene many times.

I remember when the actual engineers of these products used to participate on this forum and explain why they did what they did.
All this discussion is here deep in the boules of this forum but it really never did answer the question most ask, which design is best.