IMSB - Did I Dodge A Bullet

[Jamesp]

Originally Posted by flaps10

I worded it carefully enough that I felt like I acknowledged where the oil came from. Not trying to get into an argument James, I totally respect your input on anything I've seen here.

My point is that in a normal running engine there should be zero loose metal. Since it would seem that most wayward metal in the M96 comes from the stock IMS the last place I'm worried about pumping metal through is an already failing bearing.

Once any metal starts coming off that bearing the s*** show has begun, and the place I'd LOVE to see protected from loose metal would be the mains and rod bearings, and the LN full flow oil filter does that far better than the stock system.

Those main and rod bearings required more than a little wrench turning for me to hold in my hands.

Flaps10 (and I have to say I love your handle, being an aircraft engineer - not aerospace mind you despite the fact my disposition is manned spacecraft) don't tread lightly, and please argue. I'm an engineer, not a politician. I respect your opinion though I might not agree with it at first, I have to be convinced. I've had my engine down to the crank and back up again, complete with my own internal IMS modifications. I can confidently say I own the one and only M96-24 with a vented IMS. You chose a bearing lubrication path that I not only came up with first (to my knowledge) but also discounted due to using unfiltered oil in the lubrication system. Particulate (even very small) will damage the surface finish of bearings. As the surfaces are damaged, they begin to damage themselves (brinelling) then it's a quick trip to failure. Roller bearings having line versus ball bearing point contact appear even more susceptible to this damage. That's why I suggested the magnets - they are effective in pulling out very small particles of metal from the oil. My sense is that the configuration you chose should be fine in the long term, but if it were me I'd be sensitive to precluding particulate in the oil - hence the suggestion for magnets.

[thom4782]

This whole 'forced oiling' debate is hilarious.

Without any measurable facts put on the table, e.g., forced oiling increases lubricating film thicknesses by X percent and reduces bearing wear rates by Y percent compared to splash oiling, it's like arguing whether person gets wetter jumping in one of the great lakes versus jumping in a swimming pool.

[Smallblock454]

Originally Posted by Jamesp

I can confidently say I own the one and only M96-24 with a vented IMS.

Vented sounds interesting.

If you consider that the IMS is a sealed tube, and that the air gas volume inside is constant, you'll have a very different air overpressure at let's say 10 degrees celsius and 110 degrees celsius. At the same time you'll have a constant underpressure of around −2 mbar in the engine. Does anybody know the inner volume of the IMS tube, so we can calculate the air overpressure at different engine temeratures?

This might also be a cause why the OEM IMS sealing is stressed by temperature change.

The term vented is used as ventilation i think. How does that work? Because if you do not use a sealed bearing the pressure in the engine should be the same as in the complete engine. Or am i wrong?

PS: sorry that i use the metric system.

[Jamesp]

Originally Posted by Smallblock454

Vented sounds interesting.

If you consider that the IMS is a sealed tube, and that the air gas volume inside is constant, you'll have a very different air overpressure at let's say 10 degrees celsius and 110 degrees celsius. At the same time you'll have a constant underpressure of around −2 mbar in the engine. Does anybody know the inner volume of the IMS tube, so we can calculate the air overpressure at different engine temeratures?

This might also be a cause why the OEM IMS sealing is stressed by temperature change.

The term vented is used as ventilation i think. How does that work? Because if you do not use a sealed bearing the pressure in the engine should be the same as in the complete engine. Or am i wrong?

PS: sorry that i use the metric system.

You've got the point. I made this video a year ago

https://www.youtube.com/watch?v=qzHwWUgU37k

There are 7 short ( 2 minutes or so) videos detailing precisely what you are saying, and showing how I approached this problem. I'm at just about 3000 miles since I made this simple modification to the IMS and all is well. I redline just about every day because it is fun. Click on my name under the video if your interested in seeing what I did. There's been an implication that Porsche blew the bearing design by overloading it. I have a hard time buying that unless the mistake was assuming grease in the bearing instead of oil when doing the load calcs. That is part of the reason I went back with a sealed high temp (high temp grease and Viton seals) greased deep groove steel ball bearing with a vented IMS. The other reason is that the fully sealed bearing feature coupled with venting keeps any trash in the oil out of my IMSB.

[Jake Raby]

The groove is only 0.005" deep and the shaft they supply is definitely forged.

They made sure to leave the "Made in Germany" clear on those "drives". There's more to that story.

[Smallblock454]

Originally Posted by Jamesp

You've got the point. I made this video a year ago

https://www.youtube.com/watch?v=qzHwWUgU37k

There are 7 short ( 2 minutes or so) videos detailing precisely what you are saying, and showing how I approached this problem. I'm at just about 3000 miles since I made this simple modification to the IMS and all is well. I redline just about every day because it is fun. Click on my name under the video if your interested in seeing what I did. There's been an implication that Porsche blew the bearing design by overloading it. I have a hard time buying that unless the mistake was assuming grease in the bearing instead of oil when doing the load calcs. That is part of the reason I went back with a sealed high temp (high temp grease and Viton seals) greased deep groove steel ball bearing with a vented IMS. The other reason is that the fully sealed bearing feature coupled with venting keeps any trash in the oil out of my IMSB.

Hi jamesp,

some thoughts first:
Fluids do expand much more than air. So if you have oils in a sealed IMS tube the overpressure expands much more than you'll just have air in a sealed tube.

I would estimate that the inner volume of the IMS tube is around 0.5 litre (500 ml) and you said that there was a cup of oil in the tube - so around 100 ml? Would you agree with that? (because i want to calculate the overpressure at different temps).

If the car is on leveled ground the chains of the IMS tube run in engine oil, whereas the bearing is a little above the normal oil level. But if the car moves (accelerates, etc.), the oil level can be above the bearing. Also if the car stands or drives with the nose up a hill.

Watched your videos on Youtube:
01 http://youtu.be/qzHwWUgU37k
02 http://youtu.be/JXPMWDVn4Ec
03 http://youtu.be/PTk_xehieFc
04 http://youtu.be/Y5cgLrPsAdg
05 http://youtu.be/pKImRZ2reNY
06 http://youtu.be/SxhFdPCoYYs
07 http://youtu.be/1vrX6rmV_nI

Understand now what you mean with vented.

Where i struggle is if we really have a sealed IMS tube filled with around 50-100 ml of old engine oil, why isn't the oil pressed out of the tube / sealing, if we have overpressure (compared to the rest of the engine) in the IMS tube when the engine is hot?

If there is a way in, in general there also has to be a way out. The only way i could imagine is that materials expand when they get hot and so there is no way out, while materials shrink when they get cold and than there is a leak so that the oil can get in over a long time.

Also i'm not 100% shure that the system is 100% completely sealed system. The "weak" part might be the bolt that holds the inner part of the bearing. Also it could matter what engine oil you use. Too "thin" oil might get in faster than "thicker" oil.

You've drilled 2 holes in the IMS shaft - now i understand why you called it vented. I think it is good idea. Oil can get in and will get out when you start the engine, because of centrifugal forces, even if the oil level is a bit above the IMS shaft. Only thing to mention is that the bearing seal can be harmed over time by temperature changes and agressive oil. So it is still important to change engine oil and filters regularly.

Regards from germany
Markus

[Jamesp]

Originally Posted by Smallblock454

Hi jamesp,


If there is a way in, in general there also has to be a way out. The only way i could imagine is that materials expand when they get hot and so there is no way out, while materials shrink when they get cold and than there is a leak so that the oil can get in over a long time.

Markus

Markus, the way in and way out is at the IMS bearing seal to inner race interface. That area is sealed with a thin rubber lip much like the edge of a windshield wiper, but much smaller. When the air in the IMS tube heats up and pressurizes, that seal is no match for the delta pressure so gas escapes through it. The same thing happens in reverse when the tube cools down, only now there's a tiny bit of oil available to accompany the air through the bearing and back into the tube. That is why very nasty overcooked oil is found in the IMS when the bearing is removed. This process happens slowly over time every time the engine is heated then cooled, in other words every time the car us used.