If you like the DOF concept but have doubts about the oil feed ...

Disclaimer - I'm not an engineer; I don't even play one on tv. And although there's a train set in a box somewhere in my basement, it's been many, many, decades since I've operated it.

I agree entirely with the proposition that the IMS bearing needs lubrication. After all, it was packed with grease when brand new.

Over time, the seals (sometimes/often/always?) fail, allowing the grease to escape. The grease is replaced by engine oil which sneaks in past the same seals that allowed the grease to escape. I don't know whether the oil and grease high-5 each other as they migrate past the seal - maybe they're pals, maybe they aren't.

So, in time, the bearing is being lubricated not by grease, but by engine oil. Change the engine oil frequently, use good oil (no, I'm not going THERE), and the bearing will likely last longer, based on the premise that the oil in the bearing will, over time, be 'refreshed' with newer oil. Otherwise, that oil will become, as Pedro says, 'rancid'. And rancid is bad. The very word sounds bad. 'Rancid'.

Removing the outside seal to the bearing (new or old, ceramic or steel) will provide splash lubrication. But, splash lubrication probably isn't sufficient.

Pedro's clever DOF provides a stream of oil to the bearing (with the seal removed) which will undoubtedly be superior to 'splash' lubrication.

So far, so good.

BUT....

Using the DOF requires removing the seal. As a result, no longer are the bearing balls enclosed in a (more or less) sealed area, lubricated by the (more or less) trapped engine oil (formerly grease).

Instead, they rely on the DOF for their oil, which is probably fine, as long as the DOF is working as it should. BUT, if for any reason, the DOF should stop providing a stream of oil (failure reasons? - I dunno - a wayward piece of metal filings gets stuck in the lubrication exit hole, the line gets kinked/broken, plugged, fails, your guess is as good as mine), and you're left with splash lubrication, which is NOT going to do the trick in the long haul.

So... change the oil lots and hope that, if the grease leaves the IMS bearing, it's replaced by more or less fresh engine oil, or drop a couple grand, install the DOF and hope to heck it doesn't fail. Because, if it does, you've already removed the seal, so you're not going to have the benefit of the IMS bearing spinning in more or less contained oil - you're stuck with splash lubrication.

On a positive note, speaking of splash, do most/many/some of you remember Daryl Hannah in 'Splash', or, for that matter, 'Roxanne'. Yeah, my thoughts exactly.

Cheers.



Edited 1 time(s). Last edit at 12/12/2013 10:50PM by Roger987. (view changes)

... there's a way to monitor it.
Install an oil temp gauge in the oil line.
That way you always get to "see" the flowing oil by reading its temp.
If it ever were to stop flowing you'd see a temperature drop.
But the way that it is designed, as long as the engine is running there will be oil flowing.
We take the oil right after the filter and cooler and that's what lubricates the bearing.
Happy DOF'ing
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Thanks for your reply, Pedro. That gives rise to a few questions:

1. You wrote "But the way that it is designed, as long as the engine is running there will be oil flowing."

Is there NO chance whatsoever that, although the engine is running, the flow out the DOF unit may be stopped or greatly reduced? In short, is the DOF failure-proof?

2. Could an oil temp sending unit (or whatever it's called) be installed in the line you supply as part of the DOF? Can you offer that as an option? How much labour would be involved in completing the oil temp gauge installation, and where would the gauge be best located on a 987? (My preference would be in the same visual field as the tach and speedo.)

Your standards are too high for reality. The real question is: "is it better than the other alternatives"?

I think so.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

I wasn't expressing a standard; rather, I'm endeavouring to explore Pedro's assertion that, as long as the engine is running, the DOF will flow oil to the IMS bearing.

I'm trying to ascertain whether the cost (which I hope Pedro will estimate) of an oil temperature gauge is justified. It would, presumably offer ongoing monitoring of the DOF.

One 'alternative' may be to simply change the oil more frequently. As a DIY, that's a whole lot less expensive than the $2k for the installed DOF. Hence, my second question - why does the IMS bearing on tracked cars (and Marc W's) last longer?

I think the issue of monitoring the flow of oil s really counting angels on the heads of pins. But a flow of oil is vastly different than merely having a tiny amount of cleaner, less acid oil (changing). OTOH the issue of "why do driven cars last longer" leads me to the conclusion that splash lubrication,and low acid in oil, are real and important factors. Changing maybe less important than getting the thing out a regularly running it to burn (boil) off water and acids. And higher rpms likely splash more. The evidence is pretty strong, albeit not scientific.

But if you are already doing a clutch, the DOF is more like $1300 my guess.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Looking at Pedro's video (link below) the orifice in his DOF flange appears to be quite small. Now, I'm not second-guessing Pedro's choice of orifice diameter - I have no doubt he designed a diameter which would provide the appropriate volume and intensity of flow. But, it does seem conceivable that some sort of crud could make its way in there, and impede the flow. If that were to occur, what would remain is splash lubrication, as contrasted with the contained lubrication which had existed before the seal was removed (as part of the DOF installation).

Given that the oil to the DOF is filtered oil, perhaps the risk of the DOF orifice becoming blocked (or other DOF failure - hose etc. ) is so small as to be negligible. I don't know the answer to that. Pedro would likely have a good idea. An oil temperature gauge measuring temp of the oil flowing to the DOF would enable the owner to keep an eye on it. That interests me.

Tracked cars - assuming the seal hasn't been removed from the IMS bearing, then 'splash' lubrication wouldn't appear to come into play. And, given Pedro's hypothesis that once oil has leaked into the IMS shaft, there is no further exchange of oil from the crankcase to the inside the IMS shaft (and bearing), then it would seem that once the engine has been run good and hot, the water would have been evaporated out of the oil inside the IMS shaft, and, therefore, repeated high-temp operation wouldn't make a difference in that regard.

Grant, from your experience, do tracked Porsches tend to have their oil changed more frequently than non-tracked cars? If so, it may be that frequent oil changes could be a significant factor, as contrasted with the engines being run hard.

You're right about the cost of IMS installation being comparatively less if the labour component is allocated to a clutch job. Problem is - for those of us who don't abuse the clutch, nor track their car, the clutch won't likely need to be replaced for a long, long, time.

I don't purport to have the answers. Like you, I regard Pedro's DOF solution as the best one out there. A gauge measuring oil temp to the DOF unit (Pedro's suggestion) would provide an additional level of protection, by allowing the owner to monitor the oil flow. Perhaps Pedro might offer it as an upgrade, as he does with the IMS bearing (as part of the DOF solution).

[pedrosgarage.com]


R

the same size at the ones that are the oil jets that spray oil to the pistons from underneath or is the same size as the holes that feed oil to the cam bearings in the heads/camshaft covers.

There is a risk of something blocking the hole, any of these holes, but I know of only one case an engine was torn down to determine what was wrong and one cylinder/piston was found worn out and the owner found a small piece of metal swarf in the oil jet of that cylinder.

The oil holes mentioned above are fed filtered oil and the risk of something coming loose from the walls of the oil passages between the filter and the oil hole is slim. A bigger risk is if the oil feed to the DOF is an external line the line cracks or fails.

... the orifice in the DOF is precisely measured to provide the correct amount of oil to the bearing.
The oil feed is taken immediately after the filter and cooler and the oil does not pass over or bathe any other internal parts.
This drastically reduces, if not eliminates the issue with a clogged line.
It flows through a 2000 psi-rated oil line although it is only flowing at 20 - 100 psi (dependent on engine speed and oil temp).
You can monitor the oil flow into the bearing by installing either an oil temperature or an oil pressure gauge in-line.
These gauges are not sold as part of the kit, but we can provide them at an added cost.
I've installed one in my car, not because I distrust the DOF's ability to flow oil, but because I monitor my engine's oil temperature and it made for an easy and logical decision to install it in line on the DOF.

The assertion that as long as the engine is running, oil is flowing to the IMS bearing when a DOF is installed is true.
If the engine is running, it means that the pump is pumping oil to lubricate its innards.
The DOF is fed from one of the engine's oil galleys.

If the oil flow to the bearing stops because someone sabotaged your car, for instance, then it reverts to the way the LNE bearings have been running which they promote are good for 5oK miles.

The DOF has zero moving parts. It takes its oil supply directly from the engine, after it's been filtered and cooled. The oil line is rated at 2,000 psi even though it may run at 100 psi max. The oil line is tucked away to keep it safe from road debris.

Cars that are garage queens do in fact have higher failure rates than those that are driven regularly.
It may have more to do with the integrity of the bearing's seals than anything else.
The OEM bearing with seals intact (that have not allowed oil in) should last several hundred thousand miles, if not more.
We have seen several that have been pulled close to that mileage and when opened thy still had the lifetime grease inside and there was no oil inside the IMS.

We considered opening an orifice in the IMS shaft to test the theory of the differences in pressure.
IThe idea was eventually discarded because it meant tearing down the engine (generating very high labor costs) to be able to make such an orifice and our solution needed to be as inexpensive and non-intrussive as possible.

Keep asking questions, we'll keep on answering.
Happy DOF'ing
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Thanks Pedro, for your thorough response. From your comments, as well as others (notably March W and Grant), I think the DOF should be about as fail-safe as possible.

And I have no doubt it is a far superior approach to the IMS bearing problem than simply installing a 'better' bearing,

Garage queens - I wonder if, because they aren't driven many miles, their oil doesn't get changed often. If the owners are using 'miles driven' to determine when to change the oil, the rancid oil my be sitting in their engines a LONG time.

Lets' say you just drive your car easily on nice days. Down to the gym, over to walk the dog, etc.

Motor rarely warms up. So it dumps water and acid in the oil. Oil never gets > boiling, or nto for long. So it keeps accumulating.

So now you have a water/acid soup that your IMS bearing sits in for week on end.

BAd.

FYI - my track cars always have 3x less dilution of oil than street cars when i do oil analysis

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

(new) Boxster in Jan. of 2002 I had the oil analyzed. No reason other than I found a place just a few blocks away from where I lived that did this in house -- it was a big rig lube shop. Had the machine in the customer waiting room. The oil was the factory fill and had IIRC around 4K miles on it.

I used the Boxster to go back/forth to the office -- 20 miles round trip -- and to my errands from where I lived in Oak Grove MO to Overland Park KS and back (80+ miles round trip) and the approx. 150 mile round trip to my parent's house in Sedalia.

IOWs, no real short trips (though that 20 mile round trip work commute really is a short trip as I found out later). Even with all this usage the water content of the oil was 7%.That's roughly 1/2 quart of water. It was upon learning this that I decided then and there to not follow the Porsche 15K mile oil change and 30K mile filter change and instead change the oil and filter at 5K mile intervals.

The amount of water in the oil prompted me to monitor coolant temperature and upon doing this I found that even that 10 mile drive to the office was not enough to get the engine fully up to temperature even on a mild day. In the winter forget about it.

Even the longer drives to Overland Park or even the drives to Sedalia never saw the coolant temperature climb much above 180F. Due to the humidity and to keep the inside window surfaces clear I often had the A/C on and even though the air temperature was too cold to have the compressor on the radiator fans were on and these worked to keep the coolant temperature quite low.

Now the AOS is supposed to help keep the air pressure inside the crankcase lower than atmospheric pressure which means among other things the temperature at which the water (and unburned gasoline) in the oil boil is lower than it would be at atmospheric pressure but I suspect the AOS was not doing its job (not defective per se just inadequate/sub-par) and this allowed the water content of the oil to climb.

Where I live now the weather is milder and I can for some months out of the year drive around without having to have the A/C on. (Where I lived in MO there were approx. 2 weeks a year in the spring when I could turn off the A/C and another 2 weeks in the fall but at all other times the A/C had to be on.) So without the A/C on the radiator fans running the Boxster engine runs hotter. It gets hot enough to trigger the radiator fans which by my observation come on when the coolant temperature reaches 212F and shut off when the coolant temperature drops to 205F.

Thus the engine oil stays water free -- I believe but I've never had the oil analyzed again -- but based on the engine's longevity the 5K mile oil/filter services appear to agree with the engine and keep the acid build up to a tolerable level, one that can be I guess handled by the oil's acid fighting additives.

Well, in the case of the Boxster it has 275K miles on the odometer. I bought the car on Jan 19, 2002. This Jan. the car will be 11 years old. 275K divided by 11 years is 25K miles per year. 5K miles then accumulates in about 2.4 months. On average.

Well, there you have it, an intact IMS bearing with 275 THOUSAND MILES on it.

I can't help but think there may well be a relationship between very frequent (miles AND time) oil changes and an intact IMS bearing. Marc's engine simply isn't being exposed to acidic, watery, oil.

choose your poison!

on matters headed IMS
there's some of us that can't care less
particularly true
when 981's eschew
such data as you coalesce.

but now we're told best be aware
such horrors as we now must share
our PDK may stop
at twenty grand a pop
it's hardly likely we've a spare.

Of course, G-man(ual) is grinning ear to ear.



Edited 1 time(s). Last edit at 12/16/2013 01:50PM by Roger987. (view changes)

...and with the 981, you don't have to choose either poison.

Quote
Roger987
Over time, the seals (sometimes/often/always?) fail, allowing the grease to escape. The grease is replaced by engine oil which sneaks in past the same seals that allowed the grease to escape.
Cheers.

The seals don't fail in the way you'd expect or describe. When you pull a bearing its generally filled with oil and won't leak at all.
What happens is that when the engine is assembled, the IMS is full of air. One side is welded shut, the other side is blocked by a double-sealed bearing full of grease.
When the car is sitting level ground and has the correct amount of oil, 25-30% of the bearing is submersed in oil.
Firing up the engine generates heat. Heat makes air expand, so some of the air in the IMS as it expands gets forced out through the seals into the engine.
When the car engine is shut down and the IMS cools down, there's now lower pressure inside the shaft. Because the bearing is semi-immersed in oil some oil now gets sucked into the IMS.
This happens several times until the system balances out. There is now trapped oil inside the IMS but more importantly inside the bearing. The seals are holding, now that the pressures have equalized.
Every time the engine runs, it heats up the oil inside the bearing. Eventually this oil which is trapped there deteriorates to the point that it becomes acid, dissolving the grease.
Now the bearing is full of acidic oil which eventually eats away at the steel balls and bearing races causing tiny pits.
Eventually the pits grow and some lead to full failure of the bearing and KABOOM!
That's what happens inside.
Happy DOF'ing
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

"When the car engine is shut down and the IMS cools down, there's now lower pressure inside the shaft. Because the bearing is semi-immersed in oil some oil now gets sucked into the IMS.
This happens several times until the system balances out. There is now trapped oil inside the IMS but more importantly inside the bearing. The seals are holding, now that the pressures have equalized."

I understand your theory that once the pressure inside the IMS shaft/tube is equalized with the pressure outside, the oil (which replaced the grease) in the bearing stays put - it isn't renewed or refreshed by new oil seeping in.

But, have you any explanation as to why engines in cars which are tracked suffer far fewer IMS bearing failures, or at the very least, run much longer before failing? How would tracking the car diminish the deleterious effect of the rancid, acidic oil in the IMS bearing?

And how do you account for cars like Marc W's, which aren't tracked, yet run for over 200,000 miles without experiencing IMS bearing failure?

My sense is Marc W changes his oil frequently, and uses high quality oil. I'd also guess that owners who track their cars recognize the importance of frequent oil changes, and consequently, make sure they are done.

If that is the case, then I can't help but wonder if, even once the pressure is equalized, there is at least some exchange of oil inside the IMS shaft tube, and ultimately, inside the more or less sealed IMS bearing.

Pedro, I think you understand I'm not taking issue with your DOF solution; I'm just trying to sort out what is really going on inside the engine. Your DOF solution makes sense to me, particularly if I can monitor the engine oil flow into the IMS bearing, by monitoring the engine oil temp in the line going to the bearing.

R

if the issue is the balance of pressure on either side of the IMS shaft. Couldn't another solution be to find a channel for the pressure balance other than through the bearing?

Perhaps if there was a hole in the IMS shaft itself or a channel past the outer rim of the IMS bearing.

I cannot visualize this and I am not an engineer or even a science guy.

In another point, I have seen the oil channels in my other engine, they are VERY small. I can see the oil work past the bearings in the rocker arms etc. It would be pretty hard for there to be such a bad obstruction that the DOF would cease to function.

Now whether there is a possibility of failure of the oil line, that is another thing. But that seems similar to the liklihood that the drain plug would fall out or the filter housing cracking or a rock hitting the oil pan or.... Well, anything can happen. Plus if the hose failed, oil would be ALL OVER THE PLACE and would give you some warning - likely enough to stop the engine. But hen again, what do I know?

"A mile of highway will take you one mile. A mile of runway will take you anywhere."

As long as I stay away from the Porsche 'build your own car' software, I should be ok.

"A mile of highway will take you one mile. A mile of runway will take you anywhere."

You may not be an engineer, but did somebody spend the night in a Holiday Inn Express?

You must be kidding... I'm saving the HI Express for my big 2020 NEW YEAR'S EVE ADVENTURE !!