CSL breather tube

[Cubieman]

Doing a CSL box soon, I've got a CSL breather and had planned on modifying it to hook into the little tube/valve on a standard (US Spec.) M3.
After looking at pictures of different people's CSL box installs I've noticed the vast majority do not modify their CSL breather.
What effect does eliminating this extra tube/valve and unplugging the connection to the valve have as far a DTCs/CEL lights go?

Pics for clarity:

US Spec. :

CSL:

[ATB88]

That little extra electronic valve was actually only on later model cars (I think sometime 2004 and later?). Earlier M3s just have a hose that's exactly like the CSL's, only shorter. Since earlier M3s don't have that valve I'm pretty sure unplugging it would have no effect in terms of CEL/DTC on a normal factory tune. But even if there was, you should be running CSL software anyway, and that wouldn't know what that valve is, so definitely wouldn't throw a CEL/DTC? So with that in mind, I would think that there's absolutely no point in retrofitting it into your CSL setup, as it won't do anything.

[Cubieman]

Makes sense.

[Cubieman]

Well unfortunately I won't removing this eye sore or ill have one hell of a vacuum leak.
My 6/2004 has a different air rail with a place for this ugly/bulky breather setup. Was really looking forward to ditching this piece as well as not modifying the CSL breather. But thats cheaper than a new rail.

[terra]

If you're going to be running the CSL engine software, then you have to delete it.

[COVID-19]

What if you just buy one of those vacuum caps. (Or whatever they called)

[Cubieman]

If you're going to be running the CSL engine software, then you have to delete it.

As far as deleting it would simply unplugging the wiring connector be enough? This would also assume I modify the CSL breather on the passenger side hose connection to connect up with the other smaller diameter tubing running to the valve.
Or I could cut and plug the rubber hose from the air rail to the valve and leave the CSL breather untouched.

[terra]

The default state of that valve is open. You'll have a vacuum leak if you don't either get a pre-04 / CSL rail or plug the vacuum port.

[Cubieman]

Great, well for appearance sake I think I need a pre-04' rail. I guess I'm in the market if anyone has one.

Although theres got to be a decent way to plug that.

[jbfrancis3]

One other option: you can keep everything. To achieve a longer corrugated hose you can either: 1) buy the CSL version and swap over the hose or 2) heat up your existing hose with a heat gun (slowly) and gently stretch it; there is more than enough length bunched up in the corrugations. I recommend the latter because nothing is required for purchasing. The former will still be cheaper than sourcing an air rail. If looks take precedence then swap out the air rail for a pre -04 version.

[repoman89]

The air rail is usually dirt cheap used, got mine on the old forum for $50 shipped I think and there was more than one listed for that price. The looks are one thing but as an engineer a non-functional piece with a non-functional plug sitting there staring at me would bother the hell out of me, so the rail was a no brainer.

[ethan]

One other option: you can keep everything. To achieve a longer corrugated hose you can either: 1) buy the CSL version and swap over the hose or 2) heat up your existing hose with a heat gun (slowly) and gently stretch it; there is more than enough length bunched up in the corrugations. I recommend the latter because nothing is required for purchasing. The former will still be cheaper than sourcing an air rail. If looks take precedence then swap out the air rail for a pre -04 version.

If, as terra says, the stock position of the valve is open, do you get a vacuum leak through the PCV valve running a CSL tune?

[Cubieman]

One other option: you can keep everything. To achieve a longer corrugated hose you can either: 1) buy the CSL version and swap over the hose or 2) heat up your existing hose with a heat gun (slowly) and gently stretch it; there is more than enough length bunched up in the corrugations. I recommend the latter because nothing is required for purchasing. The former will still be cheaper than sourcing an air rail. If looks take precedence then swap out the air rail for a pre -04 version.

This is what I had planned on doing, but after Terra said that would create a vacuum leak I just bought a new rail. Just keeps adding up.

[jbfrancis3]

If, as terra says, the stock position of the valve is open, do you get a vacuum leak through the PCV valve running a CSL tune?

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. 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.

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.

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.

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.

[jbfrancis3]

This is what I had planned on doing, but after Terra said that would create a vacuum leak I just bought a new rail. Just keeps adding up.

You get a vacuum leak if you leave the bung on the air rail wide open and do not cap it off. It would pull in copious amounts of unregulated air, not allowing the idle air actuator to do its job.