Originally Posted by ptuomov

Risking reading too much into the tea leaves, I spent some time last night trying to reverse engineer the "active scavenge" system that Greg has advocated as the "racing" cure of the 928 oiling problems. I used the internet as the source, mainly photos by Rob and the various written comments posted by multiple people here on the RL. Of course, much of the system is proprietary and not disclosed, so I had to rely on my imagination heavily. Therefore, what I ended up as a result may or may not resemble what Greg installed on Rob's car.

With that explanation and keeping in mind that I've used my imagination to fill in a ton of blanks, here's what I came up with:

Attachment 687947

Since this is just a figment of my imagination, I will call the above-described system the "prankcase" evacuation system to differentiate it from anything that Greg may have actually installed on Rob's car.

Greg or Rob may
- choose to confirm that this prankcase system describes their system,
- may choose to deny that it describes their system with an explanation of what parts I just imagined,
- may choose to just deny that it describes their system without any explanation,
- or may choose to simply ignore this post.

I am obviosuly fine with any of these options, since it's their proprietary system and they are not obligated to tell me or the world anything about it. Any comment from them would be just intellectual charity. I'll just proceed to comment on the prankcase system that I imagined regardless of all this.

First, the prankcase system has a four stage scavenge pump with a single exit manifold, manufactured by Bill Dailey. The exit manifold is plumbed back to the pan. The four pickups are at the corners of the heads. The "secret sauce" parts under the valve cover scavenge near the corner head drains. In addition, the prankcase system has one of the valve covers hooked up to the oil filler neck and the other valve cover hooked up to the port between the knock sensors. The two remaining valve cover ports are hooked into the Provent via a T-fitting. The Provent drains oil to a T-fitting which is connected to one of the pump scavenge lines coming from the cam covers and going to the pump suction side. The Provent gas extraction port is connected to the intake manifold. The intent of the system is to use a pump to remove oil from the heads and return it to the sump.

Is everyone following?

Here's my mini-design review.

Positives:
+ I like the idea of venting the block from the middle of the valley. This should help reduce the need for the crankcase pulses to communicate thru the heads via the head drains.
+ I like the use of Provent as part of the system to reduce oil ingestion.
+ I like the fact that the pump outlet doesn't drain to valve cover or the oil filler neck but instead drains directly to the sump.

Negatives:
- The prankcase system scavenges the head oil drains from the top. In my opinion, it would be more effective to scavenge those from the other end of the drain channels, that is near the bottom of the block. This would avoid the active scavenge system actually pulling oil up into the heads that would've otherwise stayed in the crankcase.
- Mechanical scavenge pumps often scavenge a lot of gas as well as a lot of oil. It would be better to run an air-oil separator between the pump outlet and the sump.
- The prankcase system uses a T-fitting on one of the scavenge lines from the heads and connects that to the Provent. This has two undesirable effects. Since oil is heavier than gas, this pump stage scavenges gas only when either the Provent or the head pickup see gas. It scavenges oil only when both the Provent and the cam cover pickup see oil.
- The second undesirable effect of the scavenge line T-fitting is that the scavenge pump can easily pull a large vacuum into the Provent. This will likely mean that the Provent circuit will not flow gas from the cam covers to the intake manifold but that the scavenge pump will pull a large vacuum to whatever port in the intake manifold that the Provent gas exit is hooked up. This vacuum may then spread to the vacuum signal lines and impact, among other things, the fuel pressure regulators vacuum controlled set point.

Any thoughts, anyone?

Originally Posted by ptuomov

Risking reading too much into the tea leaves, I spent some time last night trying to reverse engineer the "active scavenge" system that Greg has advocated as the "racing" cure of the 928 oiling problems. I used the internet as the source, mainly photos by Rob and the various written comments posted by multiple people here on the RL. Of course, much of the system is proprietary and not disclosed, so I had to rely on my imagination heavily. Therefore, what I ended up as a result may or may not resemble what Greg installed on Rob's car.

With that explanation and keeping in mind that I've used my imagination to fill in a ton of blanks, here's what I came up with:

Attachment 687947

Since this is just a figment of my imagination, I will call the above-described system the "prankcase" evacuation system to differentiate it from anything that Greg may have actually installed on Rob's car.

Greg or Rob may
- choose to confirm that this prankcase system describes their system,
- may choose to deny that it describes their system with an explanation of what parts I just imagined,
- may choose to just deny that it describes their system without any explanation,
- or may choose to simply ignore this post.

I am obviosuly fine with any of these options, since it's their proprietary system and they are not obligated to tell me or the world anything about it. Any comment from them would be just intellectual charity. I'll just proceed to comment on the prankcase system that I imagined regardless of all this.

First, the prankcase system has a four stage scavenge pump with a single exit manifold, manufactured by Bill Dailey. The exit manifold is plumbed back to the pan. The four pickups are at the corners of the heads. The "secret sauce" parts under the valve cover scavenge near the corner head drains. In addition, the prankcase system has one of the valve covers hooked up to the oil filler neck and the other valve cover hooked up to the port between the knock sensors. The two remaining valve cover ports are hooked into the Provent via a T-fitting. The Provent drains oil to a T-fitting which is connected to one of the pump scavenge lines coming from the cam covers and going to the pump suction side. The Provent gas extraction port is connected to the intake manifold. The intent of the system is to use a pump to remove oil from the heads and return it to the sump.

Is everyone following?

Here's my mini-design review.

Positives:
+ I like the idea of venting the block from the middle of the valley. This should help reduce the need for the crankcase pulses to communicate thru the heads via the head drains.
+ I like the use of Provent as part of the system to reduce oil ingestion.
+ I like the fact that the pump outlet doesn't drain to valve cover or the oil filler neck but instead drains directly to the sump.

Negatives:
- The prankcase system scavenges the head oil drains from the top. In my opinion, it would be more effective to scavenge those from the other end of the drain channels, that is near the bottom of the block. This would avoid the active scavenge system actually pulling oil up into the heads that would've otherwise stayed in the crankcase.
- Mechanical scavenge pumps often scavenge a lot of gas as well as a lot of oil. It would be better to run an air-oil separator between the pump outlet and the sump.
- The prankcase system uses a T-fitting on one of the scavenge lines from the heads and connects that to the Provent. This has two undesirable effects. Since oil is heavier than gas, this pump stage scavenges gas only when either the Provent or the head pickup see gas. It scavenges oil only when both the Provent and the cam cover pickup see oil.
- The second undesirable effect of the scavenge line T-fitting is that the scavenge pump can easily pull a large vacuum into the Provent. This will likely mean that the Provent circuit will not flow gas from the cam covers to the intake manifold but that the scavenge pump will pull a large vacuum to whatever port in the intake manifold that the Provent gas exit is hooked up. This vacuum may then spread to the vacuum signal lines and impact, among other things, the fuel pressure regulators vacuum controlled set point.

Any thoughts, anyone?

Originally Posted by AO

...the valley plug and the oil neck will get covered in oil. If the get covered, then it will be difficult to equalize pressures between the crankcase and the heads..

Originally Posted by GregBBRD

This should be fun.

Originally Posted by Lizard931

One comment that I have on your comments there (it has been awhile since I have read through the thread, and looked at the few pictures), Greg used a dailey engineering pump, therefor likely has an air oil separator built onto the back of the pump to help de-aerate the oil.

Originally Posted by AO

My first impression is that you are not adequately ventilating/relieving crankcase pressure buildup. Further, the valley plug and the oil neck will get covered in oil. If the get covered, then it will be difficult to equalize pressures between the crankcase and the heads..

Originally Posted by AO

The more I think about this issue the more I am beginning to believe that the root cause of these issues lies elsewhere. That's not to say this isn't a noble endeavor.

Originally Posted by Alan

The Oil filler crank port alone is huge - pretty difficult to clog it with oil - however how useful that is depends on what happens in and above the 'filler'. The heads and crank will always equalize through the head drain ports. In fact when venting from the cam covers there will be some constant flow up the head drains - its the only way to get there (unless you are oil).

Originally Posted by Alan

Interesting that the pump can have a de-aeration feature - that can help understand Greg's report that the Provents are almost unneeded. Though as noted it suggests needing to scavenge other locations than just the heads.

Originally Posted by Alan

Given that and the 4 'corner' head drains - I also wondered about how the scavenging on a given pump port manages if it has more than one pick-up - both must be covered? - longitudinal/lateral accelerations may preclude that for a while..?

Originally Posted by andy-gts

I havent taken my car apart to see the actual internal work. but I know greg spent gobs of time just figuring the right configuration for the intra head scavenging.....then there is the crankcase ventilation that he worked eons on..... why so much crankcase pressure that seems to cause all this....is it ring and piston skirt design. does the nikasil bores help with diminishing crankcase pressure....why why why....as AO has stated ping, predetonation causes blow by to occur but in a new finely tuned engine shouldn't blow by be minimal or is blow by just normal.... I do seem to remember looking under my dads 49 dodge pickup and seeing fumes vented to atmosphere that was crankcase ventilation so I guess that answers my question...it always existss....huh

Originally Posted by Strosek Ultra

Here you have a little more interesting reading to do. Check out posts 9, 14, 84, 89, 91, 94, 102, 119, 130 in particular.
https://rennlist.com/forums/924-931-...ng-fail-9.html Ake

Originally Posted by ptuomov

Where I disagree somewhat is that the parts inside the engine spin so fast that one can't assume that pressures equate. Instead, there can be zones with persistently different pressures.

Originally Posted by ptuomov

I mostly agree. Pulling anything out of the heads, be that air or oil, is in my opinion a band-aid solution that makes the original problem worse by lowering the pressure in the cam cover. Anything that can be done to create a negative pressure differential between the crankcase (lower pressure) and the cam covers (higher pressure) helps, and anything that does the opposite hurts.

Originally Posted by ptuomov

Where I disagree somewhat is that the parts inside the engine spin so fast that one can't assume that pressures equate. Instead, there can be zones with persistently different pressures.

Originally Posted by ptuomov

It'll be even more fun if you play! ;-)

Sometimes it is difficult to tell how much pictures reveal [when you really don't feel like teaching the entire world what you just did....for free...for 3 months of your life. (Worth noting, right here, is that Andy paid zero dollars for the developmental work, but paid only for the final pieces....this was completely my own developmental work.) I was very careful about what pictures got published...and some pictures were taken and inserted during steps that didn't necessary work...intentionally. Turns out that Rob Edwards had a much better insight about the pictures, than I did. "You have to be realistic, Greg, you could provide people with exact detailed pictures of what was going on, from the outside, and they wouldn't have a clue, until they saw what was on the inside."

I know what I tried. I know what worked. I know what didn't work. There were many iterations. By the time I was done, I completely understood what Porsche had been doing and why. I understood why they couldn't "fix" the problem, without a major redesign and large investment. I understood what they did on their "Marine" engine....and why. I thought that I understood all the reasons for rod bearing failures, before I undertook this project. I actually understood only the results of the failures, not all the root causes. In short, I finally "got" it.

This knowledge then allowed me to build a "non-active pump" system. This took another 3 months of "free" effort. This was a major redesign and has very complex changes in many different places. I also have no desire to educate everyone about this system.

What few know here, and has not been mentioned, is that either system comes complete with an informal non-disclosure agreement. You are requested, as part of the purchase, to not publish pictures of the installation or the instructions. You are requested to not forward the instructions. I've got no reason to give this knowledge away. It was very difficult to figure out (Porsche couldn't/didn't do it, nor has anyone else done it) and I have absolutely no reason to give this knowledge to anyone.

Based on the pictures, I don't think Rob's car has the pump model which has the air oil-separator built in. In fact, I think (but do not know) that a four-stage pump with the air-oil separator wouldn't physically fit in that space, the separator element is long.

Look at the pictures of Rob's pump, running on the dyno and you will be really confused!

This is not my system, it's my "prankcase" reverse engineering effort of someone else's system with incomplete information. Quite possibly it's nothing like any system that is actually running anywhere. Also for the record, I had one of those expensive Dailey four-stage pumps, I would most assuredly not hook it up the like the "prankcase" system that I just drew -- I would put that pump to a more productive use.

If oil and air get pushed out from the crankcase into the heads you are by definition not adequately relieving crankcase pressure. Really? Think about that statement, some. As long as the crankcase and heads are connected by a clear airpath (not blocked by oil) the pressure is by definition, is the same, in those two "vessels'.

Any point you scavenge from the crankcase or the heads will pick up some air and some oil. The difference is in proportions of the two. The top of the crankcase, oil filler neck and the knock sensor ports, are probably points that would give you mostly air and only some oil. That's a guess. And not accurate. Remove an oil filler 'neck" and look down.

Of course it's not treating the root cause. Personally, I think all these active scavenging and ventilation Rube Goldberg's machines are like treating diarrhea with a diaper. (I guess dry sump would be the colostomy bag in that analogy.) While it's usually better than soling your pants, the solution is far from ideal. Not sure what you are saying here. Every engine has windage, scavenging, and ventilation "issues". It comes from the requirements of lubrication. Every engine has to address these issues. The solutions for the 928 engine, simply stated, were not adequate.

The root causes for oil blowing in the heads can be many. Speaking generally and not about anybody's engine specifically, a partial list of the reasons is the following:
- Someone put in really big cams with hydraulic lifters and forgot to check whether the oil pressure hole gets too close to the lifter edge
- The valve/orifice regulating the oil flow to the heads is incorrectly sized
- The crankshaft and piston movement create pressure zones that push oil and gas up the drain holes to the heads
- There's excessive blowby pressurizing the crankcase, because of poorly bedded rings, excessive oil on the bore walls, or too wide piston rings for the stroke and rpm.
Etc.

More of "etc" than any of the above? Seriously....Throwing out a bunch of basic "Engine 101" ideas and calling them the "root causes" isn't very enlightening, to the entire discussion. Makes me think about "moving you over" to the list of the people that think rods don't need to be centered, under the pistons. And those people are "really dumb".

Of course, one is better off treating these causes and not the symptoms.

There's one further issue that one should keep in mind. Not everyone's engine fills up the heads with oil. My car doesn't spray oil out of the cam cover ports, and I've spent a lot of time with it on a (chassis) dyno. The Provent is quite dry. FredR's doesn't either. jorj7's heads don't fill with oil. Etc. In fact, many 78.9mm stroke engines with good ring seal and large enough hose ventilating the oil filler neck appear to be doing just fine. To the extent there's trouble, it coincides by the ring flutter starting.

Therefore, you do not have a problem and you are wasting your time thinking about all of this stuff?

I mostly agree. Pulling anything out of the heads, be that air or oil, is in my opinion a band-aid solution that makes the original problem worse by lowering the pressure in the cam cover. Anything that can be done to create a negative pressure differential between the crankcase (lower pressure) and the cam covers (higher pressure) helps, and anything that does the opposite hurts.

See above. As long as the two "vessels" remain connected by a free air path, the pressure in the two remains the same. The "problem" with the "stock" design is that the drains quickly get overwhelmed and the pressure in the crankcase builds, until there is a huge "burp". Once that burp occurs, oil is pushed up and out of the crankcase, through the oil return holes. At that point, there is a lot of oil in the heads...and being pushed into the intake system (on a stock vehicle.) Take the time to carefully study all the iterations of the stock ventilation systems (as I had to do). Stop and consider what has to happen, for oil to be ejected from the rear right valve cover vent and make it into the intake system....and then sit there and tell me that there is no problem!

Where I disagree somewhat is that the parts inside the engine spin so fast that one can't assume that pressures equate. Instead, there can be zones with persistently different pressures. "Local pressure" differentials equalize very quickly, in an open vessel. Try blowing a huge volume of air, with lots of pressure into an empty tank, from one end. The pressure differential from one end to the other end of that vessel is extremely low. Those molecules move really, really quick.

When you actively scavenge from any point inside the engine, you ideally want to run the scavenged mixture thru an air-oil separator. If there's an active air-oil separator (I don't think Rob's has one) it runs automatically off the scavenge stage output in Dailey's pumps. If there's a Provent and if the scavenged fluid is mostly air, the scavenge pump output can (should?) be hooked to the Provent. The "prankcase system" uses the Provent in a way that doesn't fully use its air-oil separation capabilities.

What really makes no sense is scavenging the heads actively, then _not_ separating air and oil, and finally using the pump output of oil-air mixture to repressurize the crankcase. Think about it. You are trying to evacuate the crankcase and prevent oil from raising to the heads. Pulling a huge amount of air from the heads and then using it to pressurize the crankcase amounts to maximizing the oil flow up the drain channels to the heads. It's like pressure feeding the head with oil and air thru the drains. See above. You have completely missed my main reason to remove the oil from the heads.

Trying to scavenge more than one point with a single pump stage would be really dumb. Really dumb. That's why I drew the "secret sauce" pickups that are invisible in the photos to be single point pickups. I assumed that of course they would only pick up at a single point.

The truth is finally out! I'm dumb. Really dumb. Really, really dumb. But I've solved the ventilation problems, with 928 engines, with two separate systems....something that no one has been able to do....even Porsche....for over 30 years! I guess I'd rather be lucky than smart? Just a quick point.....without saying anything else. The two heads fill with oil at almost the exact same rate!

Every time I see a system described that tries to scavenge more than one point with a single stage I lose a little bit of my faith in the humanity. The internet forums are full of that kinds of plans and diagrams. For one to do that, one would have to BOTH have slept thru the high-school physics classes AND never tried to suck a milkshake with a straw that has a hole in it...

I don't think that blowby causes detonation (Do you have any idea of what a tiny bit of oil does to the effective octane of the fuel? Now push a huge volume of oil into the combustion chambers...like the GTS vehicles do....and figure out the effect!) or detonation causes blowby in a meaningful way. There's minor effects of knock retard on the combustion chamber to crankcase pressure differential, and of course long-term wear effects. But mostly it's just that blowby and detonation are both caused by too much oil on the cylinder bore walls overwhelming the oil control capabilities of the ring stock. That's my opinion anyway.

---

I think that this thread has helped clarify my thinking on this crankcase evacuation and oil drainage business. I think it's both fun and useful to try to think thru how actual and hypothetical systems flow.

Originally Posted by GregBBRD

In a two valve car?

Originally Posted by GregBBRD

I was very careful about what pictures got published...and some pictures were taken and inserted during steps that didn't necessary work...intentionally.

Originally Posted by GregBBRD

Really? Think about that statement, some. As long as the crankcase and heads are connected by a clear airpath (not blocked by oil) the pressure is by definition, is the same, in those two "vessels'.

Originally Posted by GregBBRD

And not accurate. Remove an oil filler 'neck" and look down.

Originally Posted by GregBBRD

Not sure what you are saying here. Every engine has windage, scavenging, and ventilation "issues". It comes from the requirements of lubrication. Every engine has to address these issues. The solutions for the 928 engine, simply stated, were not adequate.

Originally Posted by GregBBRD

Seriously....Throwing out a bunch of basic "Engine 101" ideas and calling them the "root causes" isn't very enlightening, to the entire discussion. Makes me think about "moving you over" to the list of the people that think rods don't need to be centered, under the pistons. And those people are "really dumb".

Originally Posted by GregBBRD

Therefore, you do not have a problem and you are wasting your time thinking about all of this stuff?

Originally Posted by GregBBRD

See above. As long as the two "vessels" remain connected by a free air path, the pressure in the two remains the same. The "problem" with the "stock" design is that the drains quickly get overwhelmed and the pressure in the crankcase builds, until there is a huge "burp". Once that burp occurs, oil is pushed up and out of the crankcase, through the oil return holes. At that point, there is a lot of oil in the heads...and being pushed into the intake system (on a stock vehicle.)

Originally Posted by GregBBRD

"Local pressure" differentials equalize very quickly, in an open vessel. Try blowing a huge volume of air, with lots of pressure into an empty tank, from one end. The pressure differential from one end to the other end of that vessel is extremely low. Those molecules move really, really quick.

Originally Posted by GregBBRD

The truth is finally out! I'm dumb. Really dumb. Really, really dumb. But I've solved the ventilation problems, with 928 engines, with two separate systems....something that no one has been able to do....even Porsche....for over 30 years! I guess I'd rather be lucky than smart? Just a quick point.....without saying anything else. The two heads fill with oil at almost the exact same rate!

Originally Posted by GregBBRD

You are putting the "cart in front of the horse", in my opinion. Before I even started to make changes, I studied all the different iterations of the factory attempts at ventilation.....for months. When Andy's engine "ejected" oil at high rpms, I did nothing, but think about what had happened and why, for about 3 months. Until you have done this and understand why each one of these changes was done (there were many, many changes....some in "mid-year", without any change to the "PET" pieces), you really don't have a chance of figuring this all out.

Originally Posted by GregBBRD

And having looked carefully at what you are saying....I'm not convinced that you are trying to figure out what is "right" about this system (that you've never seen, used, or tested) as much as you are trying to figure out what is "wrong" with what I've done. That, in itself, might be the most interesting part of this entire discussion, for me.

Originally Posted by GregBBRD

I could/probably should have called Andy and said: "Sorry. Confirmed that these engines are going to blow up, when run at high rpms, for extended periods of time....just like the have been doing since the very beginning." That's just not my style. I "undertook" the huge task of figuring out what was wrong and then designed and built pieces that solved the problems.....again, something that no one else has been able to do! And now, I "get" to listen to you tell me what is wrong with what I did? Are you ****ing serious?

Originally Posted by ptuomov

I admire your dedication to the 928 and your customers. However, I am disappointed by your admission that you are intentionally misleading the readers of this forum on a technical issue. You are writing about a system that you claim solves a problem and then in the posts that you and your customers together compose to this forum you intentionally, by your own admission, insert pictures of a system that is not what you are actually selling and that you think don't works. Do you understand what this does to your credibility as a source of technical information on this forum?



It is my understanding about fluid dynamics that fluid does not move without a pressure differential and a pressure differential doesn't exist without fluid movement. Because of this, I think that if oil and air flow from the crankcase from the heads, a pressure differential must exist. Given the velocities and the geometry, I don't think it's useful to think about the heads and the crankcase as a part of the same open vessel.



Whether or not it is accurate, it can't be verified by looking down the chimney of the running engine. You'll just see a bunch of oil churning, but you can't estimate the proportions of the two from that visual. Furthermore, the gas vent angle will materially influence what you pick up from that spot, because oil has much higher density than crankcase gasses. So what you see thru a plexiglass plate on the chimney will not tell you whether my guess is accurate or not.



Perhaps the analogy is not a good one. What I mean is that while every engine has some blowby, with a healthy level being in the neighborhood of 3% of the exhaust gas volume, unhealthy engines push much more blowby to the crankcase. While I don't know anything about your strokers, I firmly believe that the stock S4 engine blowby is normal until either of the two things happens. First, either so much oil gets thrown to the cylinder walls that the oil control is lost and the ring seal with it. Second, the rpm becomes high enough such that the rings "flutter", that is, the inertial forces on the piston rings overcome the pressure differential between the combustion chamber and the crankcase. In either of those cases, the blowby increases dramatically and all sorts of trouble starts. Attempting to relieve the symptoms with crankcase evacuation systems may mitigate the damage but will not address the underlying true causes of the problems.



I am trying to keep this completely technical as much as I can. However, I will, reluctantly, respond to ad hominem stuff in kind. Please let's avoid that.

What you think about me doesn't matter much to anyone. What I think about you matters equally little. However, our writings and behavior on this forum do lead the other readers and posters to form opinions about the both of us. I think that this matters to some extent, especially given that you don't want to describe in detail all of your solutions and you are therefore relying on your general credibility to sell your products.

I don't think that the blowby, ring flutter, and bore wall oil control are "a bunch of basic Engine 101 ideas." I think they are specific problems with the 928 S4 engine. I did the basic computations for the S4 by hand once to find the critical flutter rpm for the S4. I also use a simulator when working on my engine that not only estimates the ring flutter critical rpm but also tracks the flutter-induced blowby over the cycle. This gives and output that is a quantitative estimate of the blowby in each operating condition. Now, the simulator is not perfect and the company that sells the simulator also sells a blowby sensor that tracks the actual amount of blowby in the engine. I don't own that sensor, but I hope buy it some day.

As a side note, specifically about my turbocharged S4 engine, compensating the decline in the volumetric efficiency by increasing the boost has the positive side effect of moving the ring-flutter critical rpm to a much higher level.



I am most assuredly wasting my time. No disagreement there, this entire car project is a hobby.

Now, there's some method to my madness. Currently, I have an engien that works pretty well at the desired rpm range when it stands upright and is not subjected to acceleration forces. However, the engine would most likely not fare well on a track, with sticky tires. My goal is to first understand the 928 oiling system as well as possible and then design a solution to all the potential problems. Maybe I'll succeed, maybe I'll fail, but the fun to me is in the understanding and solving part.



I actually agree that the oil plug in the drain channel is a likely problem and that the engine will burb it into the heads under some conditions. However, the cross-sectional area of those oil drains is mcuh larger than what would be required to drain the oil if the pressure would be equal in the heads and the crankcase. I believe that the problem is caused by the pressure differential supporting the oil plugs and eventually blowing the plug out into the heads. If one eliminates the pressure differential, I don't believe this burbing can happen.



I don't agree with you that it's useful to think about the 928 engine as a single open vessel in which pressures equate immediately. There's a fast spinning crankshaft, there are pistons pumping gas back and forth, for example. These motions in my opinion can support persistently different pressure zones inside a geometrically open or connected crankcase.



Greg, please do not misinterpret me. I didn't say you are dumb. I don't know whether the system on Rob's car picks up multiple locations per stage in the heads or not. In fact, I gave you the benefit of the doubt that they only have one pickup per stage because I didn't want to assume that you are dumb.

I do however stand by my opinion that it's dumb to try to pick up oil with multiple pickups per scavenge pump stage from a system that has both air and oil. If any of the pickups catches air, one will just get air.



I don't think I am putting the cart in front of the horse. Quite the contrary. I want to first understand the problem root causes as completely as possible. With that understanding I want to design my solution for my needs. I also applaud your efforts to think first and build second.



I am absolutely trying to figure out what is happening inside the crankcase. Based on what I think right now, and fully admitting that I may be wrong, I don't think actively scavenging the heads is the best solution. I am trying to challenge and debate you here to figure this out. Perhaps you will present conclusive arguments and empirical data that will lead me to change my mind about what is happening inside the crankcase. I value understanding and knowledge much more than proving someone wrong for the sake of it -- I want to know the truth.

I admit that I am quite annoyed about your marketing antics on this forum. I don't on an emotionally level accept attempts to sell a system without an explanation how it works. On a logical level, I do understand that proprietary information can't be published freely without it losing it's proprietary nature. In any case, I am trying to leave my emotions out of it and simply find out the truth about technical matters by debating other people here, including you.

As a separate matter, I think that intentionally misleading people reading this forum on a technical matter, something to which you admitted to earlier, is completely unacceptable from any perspective.



I am challenging the assertion that you have built the only 928 engine that can run at 6000 rpm for 60 seconds in a stationary upright positition without the heads filling with oil. I simply don't believe it, and certainly you have not proven that. I think it's just over-the-top marketing hype by you.

Counterbalancing my views about your marketing antics, I do admire your dedication to your customers. We don't see many, in fact any, of your customers complaining here. That tells me something. However, let me also say that there may be some potential customers for you here that haven't experienced your dedication first hand and are put off by your marketing style to the point that they never become your customers and never experience being your customer.