Krankvent question

[archtop]

Dave I've been researching Krankvents to use on my soon to be Kraftwerks supercharged 06' and am totally confused. The general consensus is they work but don't use the front one? I ordered a set but what is best? The manufacturer says use both others say leave the front one off.

[repiv]

I think this is a matter or personal choice, or should I say, individual fears about just how much oil can come through that front breather.
The way I see it, if you've got the PCV line hooked up with a KV, much of the problem is taken care off. The front breather is just that ...... it has to "breath", which means that air must be able to move in both directions. If you put a KV on, you only have a one way valve. We've seen that the intake manifold can be subjected to at least >22 inches of Hg (vacuum). I don't think that kind of negative pressure in the crankcase is necessarily a good thing. Having an open front breather alleviates this high vacuum.
For those who feel they must install a KV on the front breather, the best option would be to orientate it so that air flows "into" the valve cover. That way, it can "inhale" when needed and prevent oil vapours from going into the air filter area, which will ultimately work its way back into the combustion chamber.
However, under boost conditions, crankcase pressures cannot be relieved since the boost pressure will keep the KV closed. Personally, I prefer to allow the front vent to breath both ways, so I installed an open (vented) catch can on it. Mind you, I also run the PCV line into the same open catch can.
For NA, using both is not so much an issue since the intake manifold is always under vacuum conditions. Crankcase pressures always have an "out".

[gomarlins3]

Now I don't remember which way I am running the front vent.

[tomauto]

The front should go from the Valve cover to the Intake manifold right?

[repiv]

The front should go from the Valve cover to the Intake manifold right?

Negative. That one goes from the valve cover to the post air filter (and pre-supercharger or turbo) area of the intake. You do not want this line under any kind of boost. Some serious crap would happen if you're boosted.

[archtop]

Thanks Dave,I'm gonna just use the PVC side Krankvent.What did you use for a catch can.
PS Thanks I'm learning a lot here. John

[repiv]

I'm using a Moroso vented catch can:
http://inlinethumb60.webshots.com/43899/2805617040025981935S600x600Q85.jpg (http://good-times.webshots.com/photo/2805617040025981935BMKBgT)

Mounted here:
http://inlinethumb31.webshots.com/25630/2217856210025981935S600x600Q85.jpg (http://good-times.webshots.com/photo/2217856210025981935wmHKix)

[gomarlins3]

I am so confused. I guess I just need to look at it this weekend when I HAVEN'T been drinking.












Since I have had them on for over three years and under boost for all that time on the track and at autoX's under WOT, I would guess I have them hooked up correctly.

[repiv]

I am so confused. I guess I just need to look at it this weekend when I HAVEN'T been drinking.





Since I have had them on for over three years and under boost for all that time on the track and at autoX's under WOT, I would guess I have them hooked up correctly.
Well, if you got the KV on in the wrong direction on the PVC line, you still have the OEM PCV valve as a back-up to prevent boost too much boost from going into the valve cover. Additionally, you would have not oil vapours escaping through that line at all and all of it would be going thru the front breather line unless you've got one on that line too.
If you have the front breather KV (if you have one here) on the wrong way, then there's no easy way for crankcase pressures to escape, which might be detrimental to the engine if you've also got the PCV one on wrong. You've essentially plugged up the PCV system.

[gomarlins3]

I followed the directions way back when when I put them on. I am just going to go check it this weekend.

[archtop]

Dave is using the Moroso setup a better idea than a Krankvent on the pvc side? It seems like there would be less issues with your setup,I like it.

[repiv]

Dave is using the Moroso setup a better idea than a Krankvent on the pvc side? It seems like there would be less issues with your setup,I like it.

I can't (and won't) say that it's a better idea. It's just the way I felt it would work best for me. Remember that I've side-stepped the whole principle of using manifold vacuum to draw vapours out. I just don't know if this is the "best" idea. It's certainly not the way that Honda's engine designers meant for it to work, but then, they never designed the engine for F.I. either.
If you go out and let your engine idle, then remove the PCV line from the intake manifold, you will notice that it already blows out very slightly. Same goes for the front breather under idling conditions. The way I see it, if there's enough pressure at idle to push past the PCV valve, it doesn't really need manifold vacuum to draw it out. As for the front vent, I can only imagine that under extreme manifold vacuum, like during high rpm engine braking, air must go INto the valve cover. Of course, there will be differences in manifold pressure and vacuum between NA and F.I.