Basically.

OK, let’s take this in the order you posted:

How much oil is up in the engine internals when the engine is running? The answer is quite a bit of it, so much in fact that Porsche used scavenging pumps in the cylinder heads to help get the oil back to the sump faster to prevent the oil pump from cavetating and creating oil foam, which neither cools or lubricates properly. On the early cars with dipsticks, people often ask if it is correct to not have oil showing on the dipsticks with the engine running, and many have commented that the digital oil level indicators show the same thing right after the engine is turned off. There is a lot of oil entrained in these engines when they are running, a lot of it because of the “flat” configuration of the cases . At any given time, more than half of the entire oil capacity is up in the engine, when it is pushed, there will be even more.

Oil mist inside the engine: Raby and LN examined this phenomenon during the development of the first generation of retrofits because they were concerned about how to properly lubricate the hybrid bearings. The rapidly turning crank and rods creates a huge amount of splash, and the rotating assembly is actually surrounded by a cloud of rapidly spinning liquid oil which creates the mist. Any racer worth their salt has had to deal with oil “windage” around the rotating assembly, and how to reduce it as it is actually eating horsepower. These studies led to a variety of ways to try and reduce this phenomenon by knife edging crank counter weights, windage trays, and even “scraper assemblies to try and divert the oil away from the rotating assembly to recover the HP lost to all the oil splashing around. The ultimate answer to controlling this is a dry sump system like those used in the Mezger turbo and Porsche race engines.

IMS shafts with LN bearings not being full of oil: The LN bearing is open on one side (towards the flywheel) to allow oiling. The shaft side is still sealed. The use of better seal material and leaving one side open dramatically reduces the tendency of the oil to migrate to the shaft and remain there. As noted earlier, a lot of these shaft unit do not run true, so allowing (or forcing) oil in to the shaft can lead to significant imbalance loads on whatever bearing is in the shaft. Some racers have gone as far as to drill holes into the shaft to let the oil out; LN took a better approach: Don’t let it get in in the first place. Because the IMS Solution brings oil into the solid bearing at whatever pressure the oil pump is generating, which would quickly flood the shaft, Raby designed the system to use a freeze plug like seal that is hammered into the shaft before the Solution it inserted to permanently seal the shaft from oil intrusion. A simple, but very effective solution to the problem.

How much oil is up in the engine internals when the engine is running? The answer is quite a bit of it, so much in fact that Porsche used scavenging pumps in the cylinder heads to help get the oil back to the sump faster to prevent the oil pump from cavetating and creating oil foam, which neither cools or lubricates properly. On the early cars with dipsticks, people often ask if it is correct to not have oil showing on the dipsticks with the engine running, and many have commented that the digital oil level indicators show the same thing right after the engine is turned off. There is a lot of oil entrained in these engines when they are running, a lot of it because of the “flat” configuration of the cases .

Exactly. There`s a lot of oil in the cylinder heads that is constantly being pumped back to the sump. As a result, when the engine starts, the scavanging kicks in too, so the oil level should be even higher in the sump than when it`s shut off... I still don`t get it. About the dipstick: how could the level be measured when the engine is on while oil is being splashed all over inside the engine case including the dipstick?

Oil mist inside the engine: Raby and LN examined this phenomenon during the development of the first generation of retrofits because they were concerned about how to properly lubricate the hybrid bearings.


Interesting, I`d like to read more about this, is this published somewhere? How did they do it? They inserted a boroscope into the case?

The oil isn't just in the heads when the engine is running. Think of the oil pump, the cooler, and all the oil passages throughout the engine. All of those add up to a fair amount of oil being in the engine, and not the sump.

True. But it`s a closed system. The oil that circulates will not flow back to the sump when the engine is off, or at least most of it remains in the oil lines, cooler, pump, etc. If this wasn`t the case, the main bearings would be starving of oil at every start up and they would fail shortly. When you pull apart an engine, especially a boxster, oil is flowing out from every oil channel and gallery producing a huge mess on your garage floor, even though you already drained the sump. When the oil pump gears are not rotating they seal off and won`t let the oil flow back to the sump. As a result, oil level should not change much during engine run vs stop, IMHO.

At high rpm's alot of the oil is in the heads waiting for the scavenge pumps to send oil back to the sump. That's the reason when you check oil level it can vary alot. If you drive at low rpm before you park or idle for half a minute before turning engine off, the oil level will show higher.

Which fails to explain why 5 min. or more is needed before the digital oil level gauge reads correctly on a hot M96.

The dipstick will show spots of oil when the engine is running, not a wet level.

If your hypothesis was the case, why do most people that race these engines both improve the baffling in the sump and deepen the sump, or move to a true dry sump it the rules allow? Because the low level of oil remaining in the sump can easily slosh to the side and uncover the oil pickup leading to pressure loss, oil starvation and some rather unfortunate damage. The oil level remaining in the sump on a running M96 is MUCH LOWER than you think.

The number one lubrication modification when seriously racing any engine is to CONTROL oil movement within the engine. Normally this. Is accomplished by literally jetting certain oil passages to limit the amount of oil going to places that don’t need much oil volume and cleaning up the passages to help get the oil to critical components like the rod and main bearings.

Some GM engines that normally carry 7 quarts of oil in the sump can get as low as 1 1/2 to 2 quarts when the engines pass 4-5K RPM because most of the oil is up in the heads; putting jets into certain oil passages cuts the oil trapped up top to 1-2 quarts, and this is in a nearly vertical v8 design engine case where gravity is your friend when it comes to getting the oil back to to the sump. Porsche’s cases are horizontal, and drain back by just gravity is not sufficient to get the oil back down to the sump, hence the scavenger pumps, and still most of the oil is still not in the sump, but up in the engine.

I don`t understand how it makes sense to say anything about oil level in a running engine using either a dipstick or a level sensor. The IMS, the sprocket and the chain are all spinning in the oil, splashing oil everywhere in the case. Itt`s like determining precisely the water level in a running washing machine with a stick. Good luck with that.

Thanks, I really appreciate that you gave a slight chance to the possibilty that my hypothesis might have some relation to reality :o

In normal conditions the oil mass is not sloshing too much, in race cars it may be, so baffling makes sense there. And so does deepening the sump, providing more oil that can be chilled more effectively. These are useful features in racing, but that doesn`t necessarily mean that these features have anything to do with the oil level or the IMS bearing`s lubrication.

I was talking about normal operational conditions though. And I still don`t get where would about 1-2 quarts of oil go when you just simply turn on the engine.

I also have difficulties in understanding how can it be claimed for sure that the IMS is lubricated by oil mist. To safely say that, you would need to insert a glass window into an engine case to see the oil level, or directly onto the IMS flange, so you can see the bearing during operation. Or you could fit a small boroscope there, but how would you do that? Once you turn off the engine, the putative window or camera would be overwhelmed by oil. It`s not a trivial experiment to do. That`s why it would be great to know where this whole oil mist theory coming from.

The GM engines cannot be compared to flat engines in this regard, because as you pointed out, in a flat engine much of the oil coming out from the heads (which is still nowhere near to 1-2 quarts because of the small orifices that won`t let the oil warm up too much in the relatively hot heads) will not return to the sump because the scavanging pumps are not running.

It is actually very easy to determine how much the oil level drops in any style engine: You build a simple sight glass level tube using flexible clear plastic tubing connected to a barb fitting in the sump cover, and the other end run up the side of the engine case and connected to the cam cover. Add oil one liter at a time and you can index mark the levels on the tube with tape or a marker. We did this all the time while running engines on a dyno to watch what level the oil dropped to at different RPM’s in order to make sure it stays away from the crank for windage control, but deep enough to keep the wet sump oil pump pickup covered. That is how I know an LS engine can drop to two quarts left in the pan at 5kRPM, and that the IMS bearing is not in the oil on an M96 engine when it is running.

So yes, you can acutally check the water level in a running washing machine if you put your mind to it. Have a good evening..............

Ok, that makes sense, so something similar to the way you`d measure the float level in a carburetor, if I understand correctly. Sorry, if I went too far with all these questions, or with questioning the status quo, but I always try to go deep into something that`s unclear to better understand it, that`s my very nature. Thanks for taking the time by the way to answer my posts, I learnt a lot actually. All the best.

I see I sparked quite the discussion! This forum is full of incredible knowledge, thank you for all of the responses.

It seems that there are a couple bearing replacement options for single-row cars?

The IMS issue has kept me from considering cars with the single row, however, maybe I should consider these while including the cost for bearing replacement.

I plan to do basic wrenching on the car, but with little mechanical experience, an IMS change is beyond my capacity. How much would I need to budget in to have the IMS changed to the best solution by an Indy? (automatic car)

The key word in your question is "Best". Before anyone can answer that question for you, you first have to decide which bearing solution is "best" for you, as there are more than several options and as many opinions.

Many people on here believe that the LN "IMS solution" is the best one. But it comes at a very steep price just for the parts. So much so that at $1849.00, parts alone cost over half as much as a used motor. So, you'd have to decide for yourself whether you're comfortable with the cost v. risk ratio.

I have a tiptronic, single row IMS. IF, and that's a big if, I decide to replace it, I'd probably go with an OEM replacement. Although I'm still curious about the cylindrical bearing. But that's my decision, you'd have to decide which replacement is best for you.

This guy makes a very good argument, even though he came to a slightly different conclusion than I did:

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

Aren't the ball bearing IMSs oiled at rest by what is in the sump and once running by an oil mist in the crankcase whipped up by the rods and crank. Doesn't that imply a drop in the crankcase oil level once running.

And the skills to make those custom parts he speaks of? We all have those.

There are at least 5 other IMS replacement offerings I know of he didn't mention. All with varying characteristics.

The investment to create a bearing assembly, test it, create tools and instructions that facilitate it being done by someone who never has done it before are worth something. To say nothing of warranty expenses and customer service costs. Maybe not to the video producer. I happened to be in touch with the guys who first created the replacement kits when they were destroying bearings and engines in their quest for the right one. They were a long time recovering those sunk costs.

I've owned 2 Boxsters. One a dual row, one a single. I totaled the first car without having replaced the IMS. Someone got a low mileage engine probably when the insurance company totaled the car. I didn't replace the second one, it was still in the car at 90k last I heard.

What is your risk tolerance? How would you feel having replaced the bearing assembly and something else takes out the engine or car? How would you feel if the bearing failed and you hadn't replaced the assembly? How long do you think you will keep the car?

A great replacement will add value but not the total cost of the replacement. A good replacement will help sell the car quicker. If I were to replace, I'd go great or at least with one that had many thousand known installs.

Crank and the whole bearing carrier is lying much higher than the IMS, and the rods are sticking out sideways, if that makes sense, so they should not whip up the oil. At least not in my 2.5 engine.

Burner is cool. I’ve wondered what happened to him. If Anyone knows, please share and my hellos to him.
So, yes, if you replace I think there are a few options, but the safe option is LN. I still balk at the price and I refuse to believe it’s fair, but so goes. I will concede that with the pricing for various LN offerings, Saving between 500-1600 dollars on the part is more than tempting to consider less expensive options.


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Hi

People keep talking about an "OEM" bearing. What exactly would that be? NSK 6204 with seals? Would it be a C3 clearance or standard?

Thanks

Berni

If you have the dual-row bearing, this is it:

NSK BD20-17
6204DUA17

Hi

Thank you

But can you actually buy either of those two bearings off the shelf now? I read that the dual row is totally NLA, and when I was hunting around could not find a 6204DUA17 unless it was from Pelican with the kit.

All the best

Berni

Yes, from what I read, 6204DUA17 was a number used specifically for Porsche. But BD20-17 is still available:

https://www.123bearing.com/bearing-BD20-17-A-DDUA17NX01-NSK.php