which ims bearing upgrade

[911monty]

James I would argue that Pedro may not be completely correct. While the thermal dynamics of heating and cooling are certainly correct I suspect there is a problem with the gas law. During the cooling cycle there are 2 phases in contact with the bearing, a gas phase and an oil phase. Since fluid flow is always to the path of least resistance then the gas phase must preferentially move through the bearing during heating and cooling cycles before the viscous oil. I suspect this eventually pushes out the grease and causes the seals to fail, then the oil simply equalizes through the bearing by gravity. A sealed bearing could very well be fine if there was a vent hole in the IMS shaft. Just my thoughts.

[Jamesp]

Originally Posted by 911monty

James I would argue that Pedro may not be completely correct. While the thermal dynamics of heating and cooling are certainly correct I suspect there is a problem with the gas law. During the cooling cycle there are 2 phases in contact with the bearing, a gas phase and an oil phase. Since fluid flow is always to the path of least resistance then the gas phase must preferentially move through the bearing during heating and cooling cycles before the viscous oil. I suspect this eventually pushes out the grease and causes the seals to fail, then the oil simply equalizes through the bearing by gravity. A sealed bearing could very well be fine if there was a vent hole in the IMS shaft. Just my thoughts.

The seals are never "perfect", they always leak. The Pelican refit kit sent me a non contact bearing that clearly would have allowed gravity to pull oil into the the IMS easily and certainly a worn seal could do the same, so this is a good point. A driving factor even with a good seal on a sealed bearing would be the delta p after running. I vented my IMS shaft on rebuild for precisely the points you make above.

[Gelbster]

It is fun to play with the "just vent it' idea. When replacing and IMSB w/o engine dismantling it is difficult to drill a small hole in a safe area of the IMS?
You could puncture the one remaining inner seal?
The there is the Vertex 'technique' at the other end of the IMS tube that involves a hammer and punch .Perhaps not.

[Jamesp]

Originally Posted by Gelbster

It is fun to play with the "just vent it' idea. When replacing and IMSB w/o engine dismantling it is difficult to drill a small hole in a safe area of the IMS?
You could puncture the one remaining inner seal? That would prevent pressure accumulating while the engine was running. If the puncture was submerged when the engine stopped ......
The there is the Vertex 'technique' at the other end of the IMS tube that involves a hammer and punch .Perhaps not.

It's quite easy (once the cases are split apart!). I've a few YouTubes on how to do it. The trick is to make sure there is never a differential pressure across the IMS bearing that serves to drive out the grease (gasp!!) in the bearing. I'll be pulling out my IMSB in the not too distant future to inspect the grease in it after doing the procedure (about 20K miles). Yeah, this is a hobby.

[Gelbster]

"once the cases are split apart"
Funny -that is cheating :-).
The trick as I said is to suggest a how-to w/o dismantling the engine. How can it be done as part of a normal IMSB replacement?

[10/10ths]

...I just bought a 2004 Boxster S and immediately shipped her to Jake Raby and Flat 6 Innovatons and had them install the "IMS Solution", which is a plain bearing fed by an oil line.

The service experience was spectacular.

Highly recommended.

Good luck.

[Jamesp]

Originally Posted by 10/10ths

...I just bought a 2004 Boxster S and immediately shipped her to Jake Raby and Flat 6 Innovatons and had them install the "IMS Solution", which is a plain bearing fed by an oil line.

The service experience was spectacular.

Highly recommended.

Good luck.

From my perspective this is an awesome engineering solution providing the contact forces in the bearing work out. I asked Jake long ago and he assured there is plenty of margin, so this appears to be the best solution going. Perhaps "overkill", but if ever you wanted overkill, this is the place. And another key here is where the oil comes from...

[911monty]

Originally Posted by Gelbster

"once the cases are split apart"
Funny -that is cheating :-).
The trick as I said is to suggest a how-to w/o dismantling the engine. How can it be done as part of a normal IMSB replacement?

Probably the only way this could be done would be to cut a channel outside the bearing race in the bearing flange.

[Jamesp]

Originally Posted by Gelbster

"once the cases are split apart"
Funny -that is cheating :-).
The trick as I said is to suggest a how-to w/o dismantling the engine. How can it be done as part of a normal IMSB replacement?

It's all about tools and IMS shafts. I'm not going to do this so I'll fess up. A fairly simple, but expensive tool could be made to drill a couple of holes from the inside of the IMS to the outside of the IMS through the sprocket splitting the twin chain sprockets as I did with mine (see YouTube). Then a (preferably high temp Viton) sealed 8 dollar greased bearing can be installed which will last for well, the life of the car. Likely. The tool is the key, the rest is just a simple bearing replacement. As an aside, a sealed bearing (as opposed to an open bearing) keeps particulate contamination out of the races which is nearly instant death to the bearing. Keeping the grease in the bearing keeps it lubricated and alive. Porsche's error? They did not account for the sealed intermediate shaft delta pressure pulling or pushing oil across the bearing. Solution? Vent the shaft.