SPOHN'S Journal II Track Demon Reborn

Originally Posted by Sh0velMan

Also, in case you're trying to suggest that not having a way for backpressure from blow-by to be relieved while under boost is going to cause issues... I really think that's taking it a bit too far.

It's the same conundrum you're in with a vacuum operated brake booster. Eventually you have to go back into vacuum briefly, or **** stops working. Same deal here. I'd bet you'd need to be in boost for several minutes without a single swing into vacuum for it to even become an issue.

Edit: OH lmao, and, if it got really bad, the pressure would escape the breather inlet anyway, as that isn't valved. So there you go, pressure can't really build up anyway. At least having the outlet plumbed to vacuum means you get a good purge of the crankcase every time you go into vacuum.

Originally Posted by Red__Zed

You get the same purge everytime you go into boost, as the crankcase is positive relative to atmosphere, with none of the pressure build up while under boost (which can actually be rather substantial).

I've not messed with this on a VHR, but just offering my opinion from the bit of experience I have with FI.


You can go pre-impeller and probably get something working, but that likely gets you into other issues.

Originally Posted by Sh0velMan

It's only positive relative to atmosphere if there is, in fact, substantial blow-by. This engine is not like older examples where there is a mechanism at work pressurizing the crankcase with intake manifold air so that all you need is a single vent, it requires vacuum from the manifold to draw out said air. Without that vacuum, there is no evacuation of the crankcase, as I've said over and over.

And as I addressed in my reply, any true pressure buildup would exit via the breather, so that's a non issue.

Originally Posted by Red__Zed

If you logged pressure in a VQ crankcase over boost, I bet you'd be surprised.

Here's one for you:

Crankcase Ventilation Mod w/Pics - Page 18 - MY350Z.COM Forums

Originally Posted by Sh0velMan

Wow, 15psi got him a 1.5psi crankcase pressurization.. that's loose as hell.