CSL breather tube

[Cubieman]

Yea, I was going to simply cap off the bung but I mainly got the air rail for the looks as well.
Now I won't have the valve/extra tube/wiring up there.

On a side note, will there be any issues with the wiring connector for the valve just being unplugged?
I am going to neatly tuck it back under the cabin air filter. The CSL engine management won't know what it is like Terra said.

[duracellttu]

Lang did my CSL conversion last year when I got his stage 2.5 head. He just extended the tube and used the OE connectors. I have no issues with this setup.

I considered getting the CSL or FSTT rail but opted for the Kassel MAP sensor instead.

[Cubieman]

Lang did my CSL conversion last year when I got his stage 2.5 head. He just extended the tube and used the OE connectors. I have no issues with this setup.

I considered getting the CSL or FSTT rail but opted for the Kassel MAP sensor instead.

Good to know, maybe this valve wouldn't have been an issue after all. But I still will be installing a pre-04 air rail.
I too am running the Kassel MAP sensor, where is your positioned? I was thinking cylinder either cylinder 2 or 3.
Do you happen to have a picture of your Kassel MAP sensor and how you routed the wiring?

[ethan]

No, and the idea of vacuum leak would be a bit of misnomer. It has to do with the purpose of that PCV solenoid on the post '04 vehicles. I haven't found any documentation on the true purpose, besides "emissions", but this is what I've worked out. I'd be grateful for any comments or critiques.

There are two sources of air in the S54:
1) ITBs - the 6 throttle valves (when they are open of course).
2) The air rail, part of the idle air system.

Generally speaking, the goal with the PCV system (positive crankcase ventilation, also called CCV) is to pull blow-by gases out of crankcase.

Yeah, I've been trying to get my head around the two versions of this system in S54s for a while too. Maybe you can help me with my understanding. I think the earlier version is a basic CCV, i.e. it vents the crankcase through the cyclone separator but isn't positively scavenged using manifold vacuum. This is because the ITB design means that - unlike normal cars - the airbox doesn't have vacuum (vacuum being a function of the restriction of airflow by the throttle plates and/or ICV depending on throttle position.) If you connected the airbox and the air rail directly (bad PCV valve), you would have a vacuum leak proper. So the PCV valve must be sealing against air rail vacuum even if not powered electrically (CSL tune).

We're not talking the crankcase here, we're talking the valve train but the term and idea remains; there are some blow-by gases (unburned hydrocarbons) in the valve train as well as oil vapor. After those gases/vapors pass through the oil separator, they are pulled out through the corrugated vent hose (the topic of this thread) and sucked into the intake manifold where they are fed into the engine.

The valvetrain and crankcase are connected, right? Is there a meaningful distinction there?

During engine idle, and at very low loads, the throttle valves aren't open. That means no vacuum in the intake manifold and ultimately, no pulling the gases out of the valve train under these conditions.

Right, so there's just positive crankcase pressure built up by mild blowby at idle which is then vented into the airbox through the cyclone separator, but not drawn out by vacuum.

So, where is there vacuum during idle and very low loads? In the idle air system. That's why you have the small corrugated line on post '04 vehicles feeding into the air rail. The air rail is giving the engine its necessary air for combustion and will burn successfully burn off the gases/vapors during idle/very low load.

That's where I think the "emissions benefit" is ultimately coming from on the later vehicles.

Makes sense to me, but I think the quotes around emissions benefit are key: in the earlier setup where the blowby would simply be vented directly into the airbox (no PCV valve, no vacuum), it would still be being drawn in by the ICV and burned. There's probably almost none that escapes to the environment. I suppose the PCV valve was probably added mid-production to appease some regulatory body: Technically without the PCV valve, you're dumping to atmosphere... it just happens to be contained in the airbox and will likely be burned.

As terra says, that solenoid is normally open. I'd imagine it will close at some % of throttle one air starts to be supplied by the throttle valves. Or the idle air actuator just takes of care of management of the idle air system in which case I'm not sure when that solenoid would close.

My guess is if the CSL tune doesn't power it directly AND it's open by default AND you don't get a vacuum leak using it with a CSL tune, it must have a mechanical spring which returns it after being closed by vacuum (or something.)

[duracellttu]

Good to know, maybe this valve wouldn't have been an issue after all. But I still will be installing a pre-04 air rail.
I too am running the Kassel MAP sensor, where is your positioned? I was thinking cylinder either cylinder 2 or 3.
Do you happen to have a picture of your Kassel MAP sensor and how you routed the wiring?

If you see the green dot in the picture above, that is the MAP sensor. It's in the 3rd ITB (counting from the front of the car).

I'll reply to your other thread with the MAP sensor wiring.

[heinzboehmer]

Good to know, maybe this valve wouldn't have been an issue after all. But I still will be installing a pre-04 air rail.
I too am running the Kassel MAP sensor, where is your positioned? I was thinking cylinder either cylinder 2 or 3.
Do you happen to have a picture of your Kassel MAP sensor and how you routed the wiring?

I placed my Kassel MAP sensor on cylinder three since that's where it's shown on Kassel's website.

Routed the wire in between cylinders two and three alongside the idle control valve line then under the airbox. Made sure to route it so that it doesn't interfere with the throttle body mechanism. Unfortunately this is the best picture I have of the wiring.

[jbfrancis3]

Yeah, I've been trying to get my head around the two versions of this system in S54s for a while too. Maybe you can help me with my understanding. I think the earlier version is a basic CCV, i.e. it vents the crankcase through the cyclone separator but isn't positively scavenged using manifold vacuum. This is because the ITB design means that - unlike normal cars - the airbox doesn't have vacuum (vacuum being a function of the restriction of airflow by the throttle plates and/or ICV depending on throttle position.) If you connected the airbox and the air rail directly (bad PCV valve), you would have a vacuum leak proper. So the PCV valve must be sealing against air rail vacuum even if not powered electrically (CSL tune).

Just to be clear both versions are a basic CCV and have the oil separator (what you're calling the cyclone since that's effectively what it is). I'm with you until the last sentence; there's no sealing of sorts - the solenoid valve is open to allow a vacuum to be applied to the CCV from the idle air system.

The valvetrain and crankcase are connected, right? Is there a meaningful distinction there?

Yes, no, and I'm not sure. Hows that for answer?

Yes, they are connected via the front cover. But the crankcase has an additional line coming out of the pan next to the dipstick and going directly into the air box. Its a small corrugated line on manual transmission vehicle and a more complicated 3 piece hose assembly is on SMG cars). That could be due to the design of the pan, or other considerations. I'm into WAG territory here.

Right, so there's just positive crankcase pressure built up by mild blowby at idle which is then vented into the airbox through the cyclone separator, but not drawn out by vacuum.

Agree

Makes sense to me, but I think the quotes around emissions benefit are key: in the earlier setup where the blowby would simply be vented directly into the airbox (no PCV valve, no vacuum), it would still be being drawn in by the ICV and burned. There's probably almost none that escapes to the environment. I suppose the PCV valve was probably added mid-production to appease some regulatory body: Technically without the PCV valve, you're dumping to atmosphere... it just happens to be contained in the airbox and will likely be burned.

Hmm, it cannot be guaranteed drawn into the ICV because the airbox is open to atmosphere. But, its going to accumulate in the air box and the idle air system is drawing from the air box, so it'll likely get drawn in one way or another.

The more I think about the more I think you are probably right with the regulatory comment; it could be some asinine rule that was implemented, or a later audit finding that necessitated immediate correction.

My guess is if the CSL tune doesn't power it directly AND it's open by default AND you don't get a vacuum leak using it with a CSL tune, it must have a mechanical spring which returns it after being closed by vacuum (or something.)

I don't follow. I understand it to be open, and the CSL tune comment is probably right in that it no longer gets energized. Don't forget there is another solenoid valve by the brake booster used to control vacuum and the control should be similar in principle. Except in one system it doesn't matter is there's no control (the emissions) and in the other it matters greatly (brake booster).

That's the reason for the large rubber vacuum hose coming out of the rear of the air rail, running along the firewall and to the booster: to give the brake booster vacuum during idle and very low throttle, which comes from the air rail.

My adds in blue. Reminder: coming from me, and that should be enough of a caveat.

[ethan]

My adds in blue. Reminder: coming from me, and that should be enough of a caveat.

Awesome, thanks for your reply. I'm with you 90% already.

Just to be clear both versions are a basic CCV and have the oil separator (what you're calling the cyclone since that's effectively what it is). I'm with you until the last sentence; there's no sealing of sorts - the solenoid valve is open to allow a vacuum to be applied to the CCV from the idle air system.

But this is really the core thing I don't quite get about our system. In a traditional PCV, the valve opens and closes to various degrees to control the amount of blowby being fed back into combustion so as not to lean out the mixture. Or it might close altogether when the airbox goes positive pressure in a turbo car e.g. so as not to stuff the crankcase and blow seals. But in the S54, the tube attached to the CCV apparently tees to the airbox and the PCV valve! So when you open that valve, aren't you applying vacuum both to the crankcase as well as the airbox? And then isn't that effectively just a second ICV bringing air in from the box and hopefully doing a better job catching the CCV outflow than if it had been dumped into the box without the tee? If so, seems like you may be right that it's not a PCV system: maybe it's actually some sort of hybrid CCV/PCV - it's sorta using vacuum to clear the crankcase, but it can't really be applying full vac to the case if it shares that line with the airbox, right? That's why I think it's a hack to make the regulators happy. Would love some help on this if anyone can jump in.

But the crankcase has an additional line coming out of the pan next to the dipstick and going directly into the air box. Its a small corrugated line on manual transmission vehicle and a more complicated 3 piece hose assembly is on SMG cars)

I believe this is the fresh air breather which is what allows air to be drawn through the crankcase and out the CCV. Has a check valve in it so that positive pressure due to blowby is forced through the cyclone separator instead of directly out the breather and into the airbox. Having said that, I've never actually blown through that check valve myself - should probably do that as a sanity check.

Edit: There's also the CPV (Constant Pressure Valve) famous for its leaking. Does that also vent the case in the scenario where we build up too much blowby for it to be effectively mitigated by the CCV?

[terra]

BMW has a quick blurb about it in the Z4M docs... though it still doesn't say much: https://www.newtis.info/tisv2/a/en/e...-valve/XiVLP9G

The purpose of the crankcase ventilation is to convey the blow-by gases into the engine's intake system. There, they are mixed with fresh air and enter the combustion chamber for combustion.

The crankcase ventilation is switched on by the activation of a valve.



In the event of faults, check the valve, feed hose, signal cables and fuse.


Note:


If fault 2FDA is entered, the cause can be a damaged or disconnected air supply line. (This cable is located directly on the engine block and it connects the intake bridge with the engine section on the opposite side). This air supply line is to be checked for leak-tightness if any fault occurs!

The crankcase ventilation valve is only fitted in the US version. The air supply line, on the other hand, is always a part of the engine independently of this.

[ethan]

For anyone who's interested, I found the attached PDF helpful for reasoning about these systems. Didn't get exactly the answer I was looking for, but apparently this configuration isn't abnormal. I guess they just compensate for the airflow back in the "WOT breather" in software.

[ATB88]

But the crankcase has an additional line coming out of the pan next to the dipstick and going directly into the air box. Its a small corrugated line on manual transmission vehicle and a more complicated 3 piece hose assembly is on SMG cars). That could be due to the design of the pan, or other considerations. I'm into WAG territory here.

I believe this is the fresh air breather which is what allows air to be drawn through the crankcase and out the CCV. Has a check valve in it so that positive pressure due to blowby is forced through the cyclone separator instead of directly out the breather and into the airbox. Having said that, I've never actually blown through that check valve myself - should probably do that as a sanity check.

Oh I always thought that the purpose of that hose was just to drain the oil than ends up in the airbox back into the oil pan so that you don't lose oil, but this actually makes sense. Cool!

[jbfrancis3]

I believe this is the fresh air breather which is what allows air to be drawn through the crankcase and out the CCV. Has a check valve in it so that positive pressure due to blowby is forced through the cyclone separator instead of directly out the breather and into the airbox. Having said that, I've never actually blown through that check valve myself - should probably do that as a sanity check.

Yes and if we checked which way it, uhhh, checked, then it would tell a lot.

I'm thinking its allows flow up towards the airbox, and checks the other way. I believe you are thinking the opposite (allowing flow from the airbox)?

[ethan]

Yes and if we checked which way it, uhhh, checked, then it would tell a lot.

I'm thinking its allows flow up towards the airbox, and checks the other way. I believe you are thinking the opposite (allowing flow from the airbox)?

Interesting! I'll just have to pull mine and check the direction of the check.

[ethan]

Stock piece from FCP for reference:



My tube:



The check valve has an arrow on it labeled "Top" (meaning to airbox presumably), but the flow through the check valve runs opposite the direction of the arrow haha - thanks BMW.




Makes sense - otherwise crankcase vapors could just bypass the cyclone separator on pre-04 cars with no vacuum draw on the case by way of this tube.

[jbfrancis3]

You were right! Also well done with pulling everything.

I understand better your comments around a fresh air breather and theory of operation. And yes, I agree the check action prevents vapors from escaping with no vacuum draw it seems. I don't envision a scenario where blowby is so excessive that you have net positive pressure in the system, and that check valve would come into play. Rather I'm under the impression vacuum is always going to exceed blow-by forces in an engine with properly sealing rings.