ptuomov

We wanted to breathe out of the neck with the largest possible hose and as far as possible from the bottom. John fabricated this metal oil filler neck version with the right kind of breather ports:

GregBBRD

I rarely comment in any of these threads......for a very good reason. I've got more time in research, building prototypes, testing, having failures, and redesigning pieces for improved ventilation pieces than anyone could every begin to imagine.

Hundred and hundreds of hours. Many failures or pieces that did not improve the "problem". And pieces that really work.

And because of this investment, I am not anxious to just tell everyone how to "fix" the problems.

However, I'll make an exception here.....because this information is spread throughout other threads.

If you haven't followed my multiple writings about the "problem", here's a quick review:

The problem stems from inadequate crankcase ventilation and inadequate oil separation from the cylinder head area....in combination.

The crankcase vents through the return oil channels from the cylinder heads to the crankcase....and from some relatively small amount of ventilation in the filler neck. Everything works pretty well...until the engine is running at high enough rpms to feed large quantities of oil to the cylinder heads. Inconveniently, when this is occurring, crankcase pressure/windage is also building and those head drains become paths of back pressure from the crankcase.

The result is that the oil level raises in the heads.

And once the oil level reaches the bottom of those plastic "snorkels" (which are hooked to the intake system), all efficient engine breathing stops. Air, with large amounts of oil in it, gets to the intake in large quantities from everything "burping". The return oil passages burp, the snorkels burp.....it's a mess.

Improving the crankcase ventilation is pretty much a lost cause. The design of the crankcase limits what one can do. Obviously, a complete (proper) dry sump system is a solution. I make various systems and pieces for this application. A complete dry sump system is complex, expensive, and finding a spot for the oil tank in a street car is tough. Driving the pump is a complex problem on a street car.

I'm a stickler for not venting crankcase fumes to the atmosphere and keeping the entire system "closed". This is tough task with an engine that has a complete dry sump system with a separate oil reservoir. Retaining an A/C system, much less a smog pump, is very tough. Complete dry sump systems on a street car, at this point, is virtually a "no go" proposition.

Another approach I've used is to remove the oil from the cylinder heads by sucking the oil out of the cylinder heads and returning that oil directly to the pan......bypassing the return oil passages. This ensures the oil level never gets high enough to block the return passages. This works extremely well...however the pieces and plumbing are a bit expensive for the average 928 owner.

It is pretty simple to install this system onto an engine and keep the crankcase "closed". This system works quite nicely on a street car....as long as the local laws do not require a smog pump.

Finally, I've got pieces to "passively" help the problem. These pieces are designed to work on "normally driven" street cars. They are not a 100% "solution", but with a combination of different internal and external devices, along with additional plumbing, very helpful in significantly helping with the ventilation problem.

Certainly, my filler neck baffle is a great place to start. This oil separator helps dramatically......right up to the point where that area of the crankcase becomes filled with so much oil that this "chimney" area in the block becomes effectively solid oil. This occurs at higher rpms and there is no complete solution to this problem. Proper windage trays help significantly. Getting the pan away from the slinging oil also helps (pan spacer and oil pick-up spacers.)

This is the extent of what I'm willing to reveal about passively (no pumps) reducing the amount of oil that reaches the intake system. Pieces and ideas fairly secretive after this point......and in this "928 world" of people copying everything I design and make, I do not desire to reveal much else.

I do have other internal and external pieces that are very effective at controlling the 928 ventilation problems. Mostly, these pieces end up inside and outside of the engines I build here. With the "proper" agreements, I do release these pieces to other people.

These pieces are very proprietary.

If you read and think about what I've written, you should be able to see the flaws in the path you are considering.

Hope this helps you!

skpyle

ptuomov, Thank you for your information and photos!

Greg, Thank you for your information, as well. However, I am getting the impression that I am just pissing in the wind. I have done some reading through Rennlist threads and have not found anything really effective at curing this issue on a street level.

I am not asking for free advice. I understand intellectual property. I am willing to pay for things. At the same time, I am trying to get a handle on exactly what I am dealing with. I appreciate your explanation.

If I understand part of what you are getting at, the long plastic oil separators become a restriction when oil packs into the heads up to the bottom edges of them. Stupid question: would putting some ventilation holes up near the top of the separator help in that instance? Meaning, provide a small path for crankcase gasses?

I only know of one passive vent system for the S3. It is/was the Sharkvent, offered by 928 Specialists. However, it is long out of production. I had heard, either in passing in one of your posts, or from another, that you were working on a passive vent system for the S3. However, that is still shrouded in mystery.

At this point, I am going to install drilled out elbows at all four vent points on the cam covers, with oil separators underneath them. I will cap the driver's side elbows. This will give me flexibility in the future if and when I figure something out. Until then, I will use inline restrictors as required to mimic the factory system.
And go from there...

The Forgotten On

On the 32 valve cars there is a block off plate on the oil pan where the fill tube for the 16V cars went.

You can use this to vent the driver's side head if you get creative with the tubing. It would give excess blow by gasses another path to get removed from the head should it fill with oil.

Experiment and get creative with a solution, just about anything is better than what these cars came with stock.

My personal choice, which some will disagree with, is to add a GTS style hose to link both head's breathing and then connect the passenger's side head to a provent.

Connect the Provent out to the smog pump and disconnect the diverter valve under the intake in order to force air into the intake instead of to the catalytic converters to keep the crank case closed.

This gives you a rudimentary crank case vacuum system built from existing OEM parts with the added benefit of none of the open crank case stink.

V2Rocket

not exactly a bolt-on solution but i've been looking at the 928 oiling issue as an extension of my project to put a 928 S3 head on a 944 block.

seems to me a good place to start if one had the opportunity would be to drill holes in each conrod "bay" in the valley of the block, tie them together and run hard lines or hoses up to the valve covers/cam housings (depending 2v or 4v).

idea being twofold...
- connecting the bays gives some venue for pressure equalization left/right and front/rear/center cylinders.
- also, connecting crankcase bays to valve covers/cam housing equalizes pressure in the head to the crankcase, so it should aid in draining the oil down the chutes (since pressure above and below the oil is now roughly equal).

then using a high capacity AOS like the provent, or a pair of those neat little BMW units tuomo found, feeding from the baffled filler neck, draining back to the pan and venting to just in front of the throttle blade.

GregBBRD

What were the results of this?

GregBBRD

GTS engines connected all the bays with a large hole in the crankcase web area.

ptuomov

It's useful to measure the blowby of the engine to know what one is dealing with. Less blowby, smaller the hole that can evacuate the crankcase at a given acceptable pressure.

I don't think that the oil drain problems that some people are experiencing are caused by excessive blowby. Absent ring flutter, the blowby flow rate is proportional to square root of the cycle average cylinder pressure. The cycle average cylinder pressure is at its maximum near the peak torque rpm. Thus, blowby is usually also the greatest near peak torque rpm. Yet I haven't seen or heard of any problems at low rpms such as that.

I can see two possibilities for high rpm crankcase breathing problems. The first is a dramatic increase in blowby when the rings flutter at high rpms. Mostly this would be because of three reasons: Too much rpm for the width of the piston rings, too many knocks, and/or too much oil on the bore wall. I know I don't have this problem because I can measure the blowby rate, and my car doesn't show that sort of a dramatic increase in my powerband rpm.

The second reason is piston pumping pulses. It's possible that the average static pressure in the crankcase and heads is low, yet the temporary dynamic pressures that the moving pistons create cause problems. The head oil drains on one side, in particular, see a full blast from the pistons pushing down in the opposite bank. Those directed pulses can cause oil drain problems, especially when external g-forces acting on the engine work against the oil drain.

If this is the problem, then using plates to shield the oil drains and to allow alternative ways for the crankcase gasses to commute between bays is the solution. Various methods for doing that include interconnecting the left and right side valve covers with large diameter hose, adding an oil pan spacer, porting the triangular breathing ports (in S4/GTs) between bays to flow better, and connecting the unused knock sensor hole in the block valley to the valve covers.

V2Rocket

my proposed system was not intended to deal with blowby/crankcase pressure per se - just to address the oil drainback issue, and to try to have a functional PCV setup via the added AOS.

i would assume that once everything was interconnected sufficiently any excess pressure in the crankcase would be vented to the intake out the AOS lines. excess being higher than atmospheric pressure.

i like Blake's suggestion of repurposing the smog pump, too.

GregBBRD

I've had a bunch of theories about how to control this issue, too.....which I've actually gone forth and tried on both the dyno and in cars which are daily driven.

When I studied the excess crankcase pressure/cylinder head filling with oil/loss of oil pressure/severe oil ejection out of the valve covers that appeared when we dynoed Andy's engine at 6,000 rpms, I spent six solid months trying to solve the problem. Six months....that's all I did. Smog pumps, vacuum pumps, stacks and stacks of passive pieces, oil returns to existing holes in the pan (which are below the oil level, BTW), oil returns to the pan above the oil level, improved oil flow through the heads, decreases in oil volume to the head, etc., etc.

From that study I came up with a "passive" system for S4 and GTS street engines.....and an "active" system, for street cars that are driven more aggressively.

So, when I ask how these ideas worked for the individual (in real life), there's a bit of a smile on my face.....because I've been there.

Rob Edwards has an interesting video on what kind of volume of oil is inside the head at rpms (we put clear tubing onto the return from my active oil removal system from the heads). You might want to take a look at that video to get an idea of how large the issue really is....it was a real "eye opener".

The Forgotten On

I have yet to add the GTS hose to my system so I have only vented the passenger's side head. At high RPMs the Provent fills with oil fairly rapidly (I don't have a drain plumbed).

Adding the smog pump helps the provent in that it puts negative pressure on the outgoing check valve to assist in evacuating gasses and prevent the top check valve from opening.

The system is in this config because I needed the car to pass smog (main reason) and the Provent was added by the PO so I have none of the stock vent plumbing to work with.

In other words, I had to make due with what I had. Turns out it worked pretty well.

After 3 months with it venting to the intake instead of the atmosphere (the way the PO had it) there is no real oil residue inside of the air filter housing.

I would say this works well for street cars but would need something better if driven constantly above 5000 RPM where oil filling the heads is the main concern.

GregBBRD

Ahhh....

Once the Provent filter gets saturated with oil it becomes a huge restrictior....the air flow through it drops way, way down.

How many miles have you put on it, like this?

The Forgotten On

A little over 3,000. I daily the car and put 50 miles on it each day 5 days a week. This includes very spirited driving in the Canyons too and from Malibu. I drain ~4 oz of oil from it every week.

It passed smog with scores around or below the averages like this with nearly 200K miles on the car.

ptuomov

When you look at the Mann-Hummel product guides, fitting a correctly sized Provent in the 928 engine bay becomes almost impossible if the power output is above stock. Take a look at those sizing charts.

The BMW separators seem to work well for us when they pick up from the top of the oil filler neck that has John's baffle box under it:


The cyclonic separators are a lot more compact than appropriately sized Provents, so that's a big plus in the 928 engine bay.

Strosek Ultra

The BMW Cyclonic oil separator part no. 11 15 1 705 237 Tuomo is refering to is a very compact and effective design. It comes in several different types but work basically the same way. The compact design will make it easy to find room for installing one or two separators in the 928 engine bay. Do watch this small video.
Åke