PCV System
05-03-2010, 02:25 PM
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PCV System
I've got a few questions about the PCV system on a B18B. However, first I'll give you a bit of background on the car. I bought the car off someone who had it turbocharged and removed all turbo parts before he sold it to me. When he had a turbo on the car he removed and destroyed the PCV Breather box on the back of the motor, and I'm having a hard time coming up with one to replace it. Now when he removed the breather box he plugged up that hole and put two barbed fittings into the back of the block for a catch can setup he had. Basically what I'm wondering is this: Can I run the engine with no breather box, and if not, is there any alternative to using this box? I'm thinking maybe a catch can setup similar to what he had installed. I'm also wondering about putting a filter on the valve cover. I've been looking at an article on this subject over at team-integra and to be honest what is posted is wrong. Let me explain:
First the article in question:
http://www.team-integra.net/forum/common_questions.asp
In this article it suggests that there is some magical force in the intake which pressurizes the tube going to the valve cover. (Not talking FI here.) This couldn't be further from the truth. From looking at the picture the author has provided I see the following happening:
(Lets assume the PCV valve is open here.)
1.The piston goes down on the intake stroke, which creates a vacuum in the intake manifold.
2. Because the PCV valve is open, vapors are sucked from the crankcase through the breather, into the intake manifold.
3.Because there is now a vacuum in the crankcase, air is sucked down from the cylinder head/valve cover area.
4.There is now a vacuum in the cylinder head/valve cover area, therefore fresh (filtered) air will be sucked through the pcv tube from the air intake pipe.
This makes the most sense to me, however I have been wrong before so I could be wrong again! So, assuming my interpretation is right, in theory the motor should run fine with no pcv system at all. I realize completely sealing off the motor could potentially be a bad idea, so I'm thinking about putting a breather on the valve cover, as well as removed on the the plugs in the back and putting a breather on there as well.
Thoughts?
First the article in question:
http://www.team-integra.net/forum/common_questions.asp
» Are breather filters really bad?
Yes they are. Read further for why.
"Here's the stock PCV diagram from the Helms manual. On the left is a cutaway view of the engine. On the right is a cutaway view of the stock intake. In the middle are the separate breather circuit and the PCV valve circuit:
All you have to learn is how the fresh air cicuit flows (follow the open white arrow) and how the crankcase vapor (with oil vapors in it ) circuit flows (follow the black arrows). Notice which circuit flows to the valve cover (on top of the engine on the left)....it's NOT the crankcase vapors. When you add a breather, you remove the line from the intake to the valve cover.
The honda crankcase breather is a POSITIVE pressure ventilation system.The air from the intake blows into the valve cover. It is NOT a negative pressure ventilation system...it does NOT suck air from the valvecover to the intake.
Breathers remove the source of positive ventilation that repressurizes the POSTIVE CRANKCASE VENTILATION (PCV) valve.
There is less pressure in the crank when you add a breather at the valve cover. The consequence of this is you get more positive blow-by from the combustion chamber past the piston rings and into the crankcase. More blow-by means less cylinder pressure...less cylinder pressure means the burn is slower and less complete...the result is more emissions and less power.
If you want to do this right and remove oil vapor from the circulating crankcase before it goes into the intake valve then, get an oilcatch can and put a breather on the catch can. Then place the catch can in between the valve cover breather and the PCV valve.
Disconnecting the breather tube, which blows fresh intake air into the valve cover, and placing a breather on the valve cover just creates more blow-by and emissions. Eventually you have so much blow-by, you lose power.
Yes they are. Read further for why.
"Here's the stock PCV diagram from the Helms manual. On the left is a cutaway view of the engine. On the right is a cutaway view of the stock intake. In the middle are the separate breather circuit and the PCV valve circuit:
All you have to learn is how the fresh air cicuit flows (follow the open white arrow) and how the crankcase vapor (with oil vapors in it ) circuit flows (follow the black arrows). Notice which circuit flows to the valve cover (on top of the engine on the left)....it's NOT the crankcase vapors. When you add a breather, you remove the line from the intake to the valve cover.
The honda crankcase breather is a POSITIVE pressure ventilation system.The air from the intake blows into the valve cover. It is NOT a negative pressure ventilation system...it does NOT suck air from the valvecover to the intake.
Breathers remove the source of positive ventilation that repressurizes the POSTIVE CRANKCASE VENTILATION (PCV) valve.
There is less pressure in the crank when you add a breather at the valve cover. The consequence of this is you get more positive blow-by from the combustion chamber past the piston rings and into the crankcase. More blow-by means less cylinder pressure...less cylinder pressure means the burn is slower and less complete...the result is more emissions and less power.
If you want to do this right and remove oil vapor from the circulating crankcase before it goes into the intake valve then, get an oilcatch can and put a breather on the catch can. Then place the catch can in between the valve cover breather and the PCV valve.
Disconnecting the breather tube, which blows fresh intake air into the valve cover, and placing a breather on the valve cover just creates more blow-by and emissions. Eventually you have so much blow-by, you lose power.
(Lets assume the PCV valve is open here.)
1.The piston goes down on the intake stroke, which creates a vacuum in the intake manifold.
2. Because the PCV valve is open, vapors are sucked from the crankcase through the breather, into the intake manifold.
3.Because there is now a vacuum in the crankcase, air is sucked down from the cylinder head/valve cover area.
4.There is now a vacuum in the cylinder head/valve cover area, therefore fresh (filtered) air will be sucked through the pcv tube from the air intake pipe.
This makes the most sense to me, however I have been wrong before so I could be wrong again! So, assuming my interpretation is right, in theory the motor should run fine with no pcv system at all. I realize completely sealing off the motor could potentially be a bad idea, so I'm thinking about putting a breather on the valve cover, as well as removed on the the plugs in the back and putting a breather on there as well.
Thoughts?
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