Deleting the Crankcase vent?

Mitco39 · 01-30-2013, 09:55 AM

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.

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

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?

GaleForce · 01-30-2013, 10:08 AM

Good question Mitch.

Mitco39 · 01-30-2013, 10:10 AM

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

Quote:

Originally Posted by modme

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

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
Who's running a catch can?

Id delete my post but I figured it might help someone out down the road.

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.

SPOHN · 01-30-2013, 01:50 PM

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

Mitco39 · 01-30-2013, 05:32 PM

Quote:

Originally Posted by SPOHN

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

L33T Z34 · 03-14-2013, 07:21 AM

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

steves · 03-15-2013, 06:12 AM

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

Mitco39 · 03-15-2013, 09:43 AM

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

steves · 03-16-2013, 06:42 AM

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

Mitco39 · 03-16-2013, 11:28 AM

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

BigT · 03-16-2013, 11:54 AM

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.

juld0zer · 03-05-2014, 06:19 PM

deleting 6 and 14 is a bad idea for NA as you'll get idling issues.
look here: HELP PLEASE: Engine Idle Problem

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?

wheee! · 03-05-2014, 06:33 PM

Interesting thread Mitch!

Mitco39 · 03-06-2014, 09:59 AM

Quote:

Originally Posted by juld0zer

deleting 6 and 14 is a bad idea for NA as you'll get idling issues.
look here: HELP PLEASE: Engine Idle Problem

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?

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.

SPOHN · 03-06-2014, 03:06 PM

Or just block off the holes in the intake tube.

01-30-2013, 09:55 AM	#1 (permalink)
Mitco39 A True Z Fanatic Join Date: Aug 2012 Location: Edmonton Alberta Canada Posts: 2,089 Drives: 40th 370z Rep Power: 132	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. With Boosted Performance's kit small filters are placed where the hose would connect to the stock intake letting it vent to atmosphere. 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? __________________ 2007 Chevy Duramax - EFILive Tuned By Me 2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her My Build --> http://www.the370z.com/members-370z-...39s-build.html

01-30-2013, 10:08 AM	#2 (permalink)
GaleForce A True Z Fanatic Join Date: Aug 2011 Location: Ontario, Canada Posts: 21,749 Drives: Varis Arising II Rep Power: 51865	Good question Mitch. __________________ >>>GaleForce's Build<<< >>>FaceBook @3GsCustoms<<<>>>Instagram @GaleForce370z<<< Varis Kamikaze-Z

01-30-2013, 01:50 PM	#4 (permalink)
SPOHN A True Z Fanatic Join Date: Feb 2010 Location: Covington, GA Age: 46 Posts: 14,844 Drives: Waiting on next Z Rep Power: 222	The only reason I haven't is why buy two filters and plugs for the intake for no purpose. But it looks cool though. __________________

03-14-2013, 07:21 AM	#6 (permalink)
L33T Z34 Banned Join Date: Jun 2010 Location: Ahnald, MO Age: 47 Posts: 387 Drives: 09 K51 G C Bw/S 6MT Rep Power: 0	I deleted hose 6 & 14. Who wants blow-by gasses to b dumped back in your Ntake @ near/@ WOT runs? Not me.... Last edited by L33T Z34; 03-10-2014 at 12:26 PM.

03-15-2013, 09:43 AM	#8 (permalink)
Mitco39 A True Z Fanatic Join Date: Aug 2012 Location: Edmonton Alberta Canada Posts: 2,089 Drives: 40th 370z Rep Power: 132	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 __________________ 2007 Chevy Duramax - EFILive Tuned By Me 2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her My Build --> http://www.the370z.com/members-370z-...39s-build.html

03-15-2013, 06:12 AM	#7 (permalink)
steves Base Member Join Date: Jan 2013 Location: Australia Posts: 11 Drives: 370z Rep Power: 13	What about the coolant running through the throttle bodies? Is this to keep it cooled or heat it up?

03-16-2013, 06:42 AM	#9 (permalink)
steves Base Member Join Date: Jan 2013 Location: Australia Posts: 11 Drives: 370z Rep Power: 13	Ok, sounds about right. Any advantages in removing this in hotter climates?

03-16-2013, 11:28 AM	#10 (permalink)
Mitco39 A True Z Fanatic Join Date: Aug 2012 Location: Edmonton Alberta Canada Posts: 2,089 Drives: 40th 370z Rep Power: 132	It would probably help a tad bit with IAT's but I am not sure how much or if it is even noticeable. __________________ 2007 Chevy Duramax - EFILive Tuned By Me 2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her My Build --> http://www.the370z.com/members-370z-...39s-build.html

03-16-2013, 11:54 AM	#11 (permalink)
BigT Enthusiast Member Join Date: Jan 2012 Location: NJ Posts: 469 Drives: 98 2g DSM Rep Power: 14	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.

03-05-2014, 06:19 PM	#12 (permalink)
juld0zer Enthusiast Member Join Date: Nov 2012 Location: Sydney Posts: 428 Drives: 11 Nissan 370Z MB M6 Rep Power: 139	deleting 6 and 14 is a bad idea for NA as you'll get idling issues. look here: HELP PLEASE: Engine Idle Problem 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? Jordo! likes this.

03-05-2014, 06:33 PM	#13 (permalink)
wheee! A True Z Fanatic Join Date: Sep 2009 Location: Mod Capital of Canada Age: 58 Posts: 7,354 Drives: cars. lots of cars. Rep Power: 40182	Interesting thread Mitch! __________________ H&R / Stillen / Berk / HKS / Swift / Michelin / UpRev / SPC / Amuse Rep / Seibon / Fringe XVO / TWM / more... My Journal

03-06-2014, 03:06 PM	#15 (permalink)
SPOHN A True Z Fanatic Join Date: Feb 2010 Location: Covington, GA Age: 46 Posts: 14,844 Drives: Waiting on next Z Rep Power: 222	Or just block off the holes in the intake tube. __________________

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