DIY Solution to M54-M52TU CCV problems

[Bmwe5320023.0]

Originally Posted by Xelo

I must revive this thread upon new findings regarding the amount of vacuum the M54 pulls after this modification.

In latest SIB 110308 BMW states the amount of pressure/vacuum inside the M54 crankcase must be ~16 mBar (that is 0,48inHg). As measured while using the FRAM FV345 PCV valve, the vacuum is 12-15 inHg (or +500mBar). That is over 30x the limit the engine was designed for, this is insane!

And this amount of vacuum is at idle ! Please imagine what letting off throttle/decelerating at 3-4-5K RPMs will do to the level of vacuum
This will no doubtly damage seals/orings inside and deprive the oil pump of oil, lowering oil pressure for brief moments on decelerations.

I have not met another engine in the world where upon opening the oil cap that much vacuum is present. This is wrong and must be addressed as this modification transforms a Closed Crankcase Ventilation system into a Positive Crankcase Ventilation system, but without all the elements needed for such a PCV system to work.

Inside classic PCV systems/engines, there is a continuous air circulation inside the crankcase because there are 2 holes letting the crankcase breath: first one lets the blowby exit being sucked by the intake through the PCV and the 2nd one lets fresh filtered air inside the crankcase in order to: 1) limit the amount of vacuum being built 2) properly vent all areas of crankcase in a wide range of engine RPMs
Usually this 2nd hole sucks air from the intake downstream (after) of filter/MAF/MAP but before (upstream) throttle - where the vacuum is low when throttle is closed.

By removing the CCV (OK), plugging the dipstick drain hole (not OK) and rerouting the crankcase blowby venting directly into the intake (OK) you have designed an incomplete PCV system. One has to allow the block/crankcase to be vented with fresh air from a clean source otherwise it would be like sucking air from a plastic bottle: something/somewhere will colapse and those will be either your VCG or rear main seal.

By venting the block through a 2nd hole you are punching a hole in that plastic bottle you are sucking air out of: while the sucking is still there, the bottle will not collapse anymore as some small venting/air is let in keeping it vented.

If this worked for some of you it does not mean is a right thing, the engine was not designed for this amount of vacuum - and this is BMW's statement as you can see.

You need to provide clean measured source of air to the crankcase while using the PCV. This can be easily done through the vacuum F connector in the intake boot with a T connected to the dipstick previously plugged while a check (one way) valve is installed to prevent air/pressure from the crankcase going up to the intake.

Here's my test. So I just measured directly at the hose that goes into the distribution box that's connected to the manifold.
So manifold is pulling 16-17 inHG instead of 0.48 inHG?
Does the original CCV system then blocks the vacuum at the diaphragm and doesn't let it pull so much from valve cover?
I guess to confirm all we need to do is have someone with the stock CCV system measure the vacuum?
Which is probably going to be like bmw says 0.48inHG?
So on this case it's true, the vacuum with this mod is 30 times stronger.
Now how much vacuum is safe for the seals?
Just for fun I sucked on that gauge as hard as I could, and it showed 23 inHG lol! So it relative terms that I can relate to, it's not that much suction...



But it's probably enough to stop the oil consumption...
Here's CN90's picture, numbers are just examples.
BTW I wonder if CN90 is still around with thus mod?

Fifty150hs I think your mode is a bit different because you installed a catch can??

[Fifty150hs]

Originally Posted by Bmwe5320023.0

Here's my test. So I just measured directly at the hose that goes into the distribution box that's connected to the manifold.
So manifold is pulling 16-17 inHG instead of 0.48 inHG?
Does the original CCV system then blocks the vacuum at the diaphragm and doesn't let it pull so much from valve cover?
I guess to confirm all we need to do is have someone with the stock CCV system measure the vacuum?
Which is probably going to be like bmw says 0.48inHG?
So on this case it's true, the vacuum with this mod is 30 times stronger.
Now how much vacuum is safe for the seals?
Just for fun I sucked on that gauge as hard as I could, and it showed 23 inHG lol! So it relative terms that I can relate to, it's not that much suction...



But it's probably enough to stop the oil consumption...
Here's CN90's picture, numbers are just examples.
BTW I wonder if CN90 is still around with thus mod?

Fifty150hs I think your mode is a bit different because you installed a catch can??

Mine is pretty much the same except the catch can is in line between the output of the PCV valve and the return into the intake manifold. The Cn90 mod runs the hose from the PCV outlet directly to the intake manifold. The catch can in my system just extends the hose from the PCV outlet and the inlet to the intake manifold. No difference in vacuum.

[Bmwe5320023.0]

Sounds good, we've got same vacuum, that's good, you've had it for many years, gives me confidence
My setup I'd like cn90 then.
I drove around and according to torque app, the vacuum goes up to 27inHG, but often times, whenever you accelerate, it goes to only 1-2 or around that point.
We'll see what happens...I've got no leaks right now, so it will be easy to tell.

[Fifty150hs]

Checked my vacuum today. Put an oil cap on that I had drilled a hole in and plugged in a vac gauge. I was pulling 1" hg at idle. That's only about double the vacuum it's supposed to be pulling. It's more, but certainly not excessive.

[Bmwe5320023.0]

Thanks for checking. I bet the oil catch can must be letting the air through. Or there's gotta be a vacuum leak?

[80stech]

Yes, there must be a leak somewhere. There is absolutely no way that a PCV is regulating the vacuum in the crankcase to 1".

Actually I forgot that I swore to myself never to post again in this ridiculous thread!

[Fifty150hs]

Originally Posted by Bmwe5320023.0

Thanks for checking. I bet the oil catch can must be letting the air through. Or there's gotta be a vacuum leak?

Catch can is sealed with an O ring. If I had a vacuum leak I'd be throwing codes. I'm not. The line essentially runs from the valve cover, through the catch can and into the intake manifold. When I first tested before the mod I got 1/2" hg vacuum. The system is definitely working as I get oil in the catch can. If I tested vacuum by porting directly into the intake manifold I would expect 17" or more.

[Bmwe5320023.0]

Originally Posted by 80stech

Yes, there must be a leak somewhere. There is absolutely no way that a PCV is regulating the vacuum in the crankcase to 1".

Actually I forgot that I swore to myself never to post again in this ridiculous thread!

[Bmwe5320023.0]

Originally Posted by Fifty150hs

Catch can is sealed with an O ring. If I had a vacuum leak I'd be throwing codes. I'm not. The line essentially runs from the valve cover, through the catch can and into the intake manifold. When I first tested before the mod I got 1/2" hg vacuum. The system is definitely working as I get oil in the catch can. If I tested vacuum by porting directly into the intake manifold I would expect 17" or more.

Gotta drill the cap haha! I'll post results...

[Bmwe5320023.0]

Was also thinking if anyone considered a vacuum adjustable valve?
Control Devices VR Series Brass Vacuum Relief Valve, 0-30" Hg Vacuum Range, 1/4" Male NPT https://a.co/d/2Qi4gNR