Look what's popped up, I haven't been around nor seen this in a while.

Greg, in the diagram above, EVERYTHING in yellow is AFTER the MAF, thus, it's all metered air - *EXCEPT FOR*...

...look the driver-side rear, it is pulling air into the engine BEFORE the MAF, thus, it's not metered/measured by the MAF.

Because it's not measured by the MAF, and is entering the cylinders, the engine will be running leaner than what the MAF is reporting to the brain.

Finally, looking at my earlier diagram at Red #1, that port is pulling/causing a vacuum in the oil-filler neck, and then down into the crankcase, and then up into the valve covers, and is sucking un-metered air in thru the driver-side rear which is open to the atmosphere, and subsequently burned in the cylinders, causing a lean condition.

What do you think?

 

oups...

 

Bonjour,
As I was sucking oil from the crankcase, I finally decided to do this :

On my last track day, I sucked nothing in the catch can and very few oil in the Provent. But the car drink the same amount of oil as before : about 1.25 quart.
So now burned oil could come from 2 remaining path : the passenger side aft cam cover elbow or piston rings...
I removed the catch.
My next plan will be to try to install a catch can in between the passenger side aft cam cover elbow and the intake to verify that a lot of oil come in the engine from there. Maybe oil, as Greg explained, accumulated in the passenger side head (not in the driver side because I have no oil that goes out from the driver side aft elbow) and as been sucked by the intake?
Have a great weekend,
Raphaël

 

Bonjour,
Finally, I did this :


During my last track day (about 300km on the track), I found the filter of the provent oily but I get very few oil in the bottom. And I found a few oil in the catch can...
However the car still drunk about 1 quart of oil. Oil consumption on track is not increasing.
It looks like more oil is ingested where there is the catch can. Maybe the catch can is not stopping oil going to the intake? Next change will be to swap the catch can and the provent to see what's going on.
But I'm close to conclude that the main quantity of oil is ingested by the piston rings...
This winter I will check the compressions.
Have a great day,
Raphaël

 

Did you fix your air-leak at the rear valve cover?

 

SwayBar,
You speak about the link I did from the rear driver valve cover to the airbox as Greg advised me?
Looks not affecting AFR/lambda. I think I already check that but I just disconnected and cap it and I will check again this week and I will confirm to you that there is no change.
Have a great day,
Raphaël

 

Yes, Greg is wrong - not sure why he's having difficulties understanding such a simple system.

You are drawing unmetered air into the engine thru the rear passenger valve cover.

Think about it - where the white arrow is pointing, how is that air being metered via the MAF?

It is not, and that air is being drawn into the engine via the vacuum port at the front of throttle body on the right in the diagram, therefore, it is a vacuum leak.

You don't need an AFR meter to tell you that your crankcase is not sealed.

 

Bonjour,
I see NO difference at all on the AFR with the connection to the airbox or without it. So I let it.

I'm pulling the engine. I removed the intake and it was very different that other times...
I found oil only in the middle of the throttle body.
All the rest of the TB, was... completely dry... no oil at all around the connection on the front of the TB... and on the sides... usually the sides of the TB were oily...
And the intake, instead of being oily was completely... dry!!!
I was planning to come back stock after engine rework but maybe I will maintain this set up.

Have a great week-end.
Raphaël

 

Sorry, have not been paying attention.
Rest assured, Greg understands this, completely.
Whoever drew the diagram simply drew the white arrow pointing in the incorrect direction
At idle and low rpm conditions, there is no airflow through the driver's rear connection....in either direction.
As crankcase pressure builds (rpms go higher), the higher pressure at the rear of the driver's valve cover vents to the low pressure area in the air filter.

This drawing only works with a set of my valve cover oil separators.
Otherwise, oil will be sucked into the. intake, exactly like it is, in the stock configuration.

 

Greg,
Yes... I confirm your cam cover battles works great. After each track cession, I get very few oil in the catch can.
I added a catch can to increase the volume of air in order to try to remove more oil... but it does not extract more oil... However the intake is dry...
Not easy to understand how it works...

Have a great day,
Raphaël

 

Perhaps that is why high dollar Porsche engineers could not solve it....
Took a simple mechanic in Southern California.

 

The S4 breather system is yet another example of Porsche un-developing the 928.......the early 16V system is MUCH better...same for the oil pan....

If they kept the early breather and oil pan designs, I wonder how many 32V cars wouldn't have blown up.....or probably taken much longer to blow up?

 

The 2 valve engines actually have the same issues...perhaps even worse, because there are no "vents" on the tops of the cam carriers.
They just are unable to "collect" 4-5 quarts of oil in the cams carriers, like the 32 valve engines do.

 

Bonjour,
Now after engine rework I did this :

Few oil is trapped in the can but on a regular basis, even if I drive cool...
Last track day + a 1000 miles travel, the engine drink only a third of a quart (at least one good quart before engine rework)!
That's cool!!!

Have a great week end,
Raphaël