Nissan 370Z Forum - Deleting the Crankcase vent?

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Deleting the Crankcase vent?

Just looking for your thoughts on this, maybe someone who had the valve covers off can chime in. If you look there is a PCV system as illustrated by hose 1 and hose 13. These take the crankcase gasses and route them into the intake via the PCV Valve (item 3).

But now if you look at lines 6 and 14 they appear to also run from the crankcase to each of the intake tubes, this time with no valving at all.

http://img.photobucket.com/albums/v2...ps56d1b153.jpg

With Boosted Performance's kit small filters are placed where the hose would connect to the stock intake letting it vent to atmosphere.

http://img.photobucket.com/albums/v2...psd751c726.jpg

But why is this even needed if you have the PCV system as shown by lines 1 and 13? Could one just not block these lines and let the PCV valve take care of the crankcase gasses?

I am curious if maybe there is another reason for these valves and a picture of the underside of the valve covers would provide the answer. Or maybe someone has done this already?

Good question Mitch.

Found what I was looking for, another reason to use the search :cool:

Quote:

Originally Posted by modme (Post 1161884)

Actually, crankcase pressure/airflow are completely different from NA versus FI. In NA, you will never reach positive pressure inside the intake manifold. During WOT, pressure in the manifold will drop down to zero, the PCP valve will close and crankcase air will vent minimally through the crankcase vent.

However, in FI, your manifold pressure will reach up to 12 psi or whatever boost level you are running during WOT. So now the PCV valves close, but you have significantly more pressure venting from the crankcase vent to the air intake piping. How much oil vapor is blown through during this process, I am not sure.

Quote:

Originally Posted by wstar (Post 1161908)

Yes, that's basically true. Given positive manifold pressures from FI, I wouldn't be surprised if some of your crankcase venting ends up exiting the fresh air inlet tubes under hard acceleration as well (as you'll be building crankcase pressure from blowby, but the positive manifold pressure will keep the PCV valve forced closed). I doubt the factory puts one-way valves in them (which aren't a great idea), so you might want to experiment with canning those as well.

Another thing could affect all of this on NA cars is your driving patterns I guess. Engine braking produces more vacuum than idle or steady-state driving (faster rate of PCV system flow), whereas hard accel (WOT) produces almost no vacuum (slower rate of PCV system flow). If you use engine braking a lot, you could be scavenging from the crankcase at a higher average long term rate.

This was from
http://www.the370z.com/forced-induct...tch-can-2.html

Id delete my post but I figured it might help someone out down the road. :icon17::tup: It also makes me wonder about TT kits that keep this crankcase vent hose in their intakes, when you do this your essentially loading your crankcase up with the same amount of boost that your intake tubes are seeing, and this cannot be good for the seals. Not to mention your not working the piston both ways as they try and move the air about the crankcase.

So if you wanted to do the Catch can setup and vent the outlet to ATM then there is no reason you would need to run this second breather.

The only reason I haven't is why buy two filters and plugs for the intake for no purpose. But it looks cool though.

Quote:

Originally Posted by SPOHN (Post 2138915)

The only reason I haven't is why buy two filters and plugs for the intake for no purpose. But it looks cool though.

Its more for the Forced Induction guys who dont have the inlets on the boost tubes :)

I deleted hose 6 & 14. Who wants blow-by gasses to b dumped back in your Ntake @ near/@ WOT runs? Not me....

What about the coolant running through the throttle bodies? Is this to keep it cooled or heat it up?

Its to keep them from freezing up in colder climates. You dont want to have one of those valves stick open, it would make for a baaaad day. haha

Ok, sounds about right. Any advantages in removing this in hotter climates?

It would probably help a tad bit with IAT's but I am not sure how much or if it is even noticeable.

I would leave the crankcase breather's there, especially in a boosted car. Recirculating them reduces stress in the block and helps the piston rings seat.

deleting 6 and 14 is a bad idea for NA as you'll get idling issues.
look here: http://www.the370z.com/engine-drivet...e-problem.html

even if you disconnected them from your intake and whacked a small filter on the ends, you'd be creating another problem - unmetered (hotter) air entering the engine.

it's all part of a circuit where 1 and 13 are under vacuum and suck the ccv gases in to be burnt up. 6 and 14 are the fresh air supply lines, to replace the ccv gases, oil vapour etc sucked out via 1 and 13. ever wondered why you dont see oily gunk in your intake pipes?

Interesting thread Mitch! :tup:

Quote:

Originally Posted by juld0zer (Post 2721265)

I forgot about this thread. After thinking about it a year later and reading your post I agree. 6 and 14 with the check valves are only able to "suck" air out of the crankcase. When running boosted under load the PCV valve closes and all is well in the world. So when you are idling you are sucking air in through lines 6 and 14 and into the intake manifold.

:tiphat:

Or just block off the holes in the intake tube.

Quote:

Originally Posted by SPOHN (Post 2722897)

Or just block off the holes in the intake tube.

But if you do that then lines 6 and 14 (and the filters on them) are going to be exhausting much more than they already are, which could cause oil vapour to start making a mess of the engine.

Yea I just haven't seen that over a period of a year in track environment with my car. And the front two are freely open.

Quote:

Originally Posted by Mitco39 (Post 2722910)

But if you do that then lines 6 and 14 (and the filters on them) are going to be exhausting much more than they already are, which could cause oil vapour to start making a mess of the engine.

:iagree: yeah, why would you do that?

Quote:

Originally Posted by SPOHN (Post 2722956)

Yea I just haven't seen that over a period of a year in track environment with my car. And the front two are freely open.

Same here. minus the crazy track time.

venting the PCV valve will not harm the motor, only reason why its recirc into the intake is for emissions purposes

just whatever you do dont close the PCV, either have it recirc or vta, if you close it off entirely, you will harm the motor

I always run PCV systems as they come from the factory, no harm done. When I turbo the car, I just relocate the fresh air vents to pre-turbo how they come on factory turbo cars.

The oil going through the intake is extremely minimal. It builds up a thin residue inside the piping, but its never slowed my car down or caused a failure. I never really understood all the stress over catching it in a can and all the hoses all over the place. But I wouldn't eliminate the setup either.

The way the BP turbo kit has you do it makes plenty of sense since the turbo inlet is rather far away from that point.

Quote:

Originally Posted by juld0zer (Post 2721265)

Sorry, you're wrong. I've had breather filters on my valve covers for over four years w/thousands of miles. No idle issues and no "oil residue" in my engine bay. I don't want oil residue in my intake pipes and oil/dirt/gunk making my throttle bodies stick.