Noob... What is PCV system

[kfr291]

so as the title says. i here alot of talk about the PCV system. what is this exactly, what does it do for our cars? Also is it only seen on turbo cars?

[obermd]

It stands for Positive Crankcase Ventilation. It's part of the emissions control system on all cars in the US. What it does and how it works I'll have to leave for one of the more technical people here.

[cruzers]

I believe it recirculate unburned gas back into the engine.

[jblackburn]

I believe it recirculate unburned gas back into the engine.

No. That's EGR. Exhaust gas recirculation.

PCV stands for positive crankcase ventilation. It captures the exhaust and oil vapors pushed past the rings and valves and returns it back to the intake manifold to be burned. Some cars have a "catch can" system to separate out the oil droplets so they don't gunk up the intake manifold and intake valves.

It is illegal to vent to the atmosphere because it contains noxious gases and droplets of oil.


Sent from AutoGuide.com App

[kfr291]

so ( minus the catch can) does the pressure of the gas open a value allowing it to come back to the top of the manifold to get burned aggin? or is it controled by computer.

[jblackburn]

It is constantly pulled into the intake by vacuum. No "valve" that closes persay.

In a turbocharged car vacuum comes from 2 sources. The intake manifold at idle alone. And the intake side of the turbo when the engine is under boost (since the intake manifold has positive pressure going through it).


Sent from AutoGuide.com App

[rodneyiii]

It is constantly pulled into the intake by vacuum. No "valve" that closes persay.

The PCV valve is the controlling component in the system. It is a spring-loaded restriction in the vacuum path of the PCV system that keeps it from creating an uncontrolled vacuum leak. Manifold vacuum is pulled through the crankcase from a tube connected to the air cleaner housing to provide fresh, filtered air. In a properly operating engine, the amount of oil vapor is minimal and will easily blend and burn with the intake manifold air without leaving massive oil deposits as some people perceive. The PCV system performs two main functions. First, it draws piston blow-by gasses and oil outgassing vapors out of the crankcase to be burned. Second, by keeping the crankcase under a slight vacuum, oil leaks from other engine gaskets are kept to a minimum. Otherwise, positive pressure in the crankcase would force oil out through the gaskets over time.

What it does and how it works I'll have to leave for one of the more technical people here.

How did you get "Gearhead" status without knowing engine basics?

[kfr291]

The PCV valve is the controlling component in the system. It is a spring-loaded restriction in the vacuum path of the PCV system that keeps it from creating an uncontrolled vacuum leak. Manifold vacuum is pulled through the crankcase from a tube connected to the air cleaner housing to provide fresh, filtered air. In a properly operating engine, the amount of oil vapor is minimal and will easily blend and burn with the intake manifold air without leaving massive oil deposits as some people perceive. The PCV system performs two main functions. First, it draws piston blow-by gasses and oil outgassing vapors out of the crankcase to be burned. Second, by keeping the crankcase under a slight vacuum, oil leaks from other engine gaskets are kept to a minimum. Otherwise, positive pressure in the crankcase would force oil out through the gaskets over time.

How did you get "Gearhead" status without knowing engine basics?

Ok this makes sense. i will never touch the dam system but i always hear people talking about it so i figured i ask about it.... when was the idea put into practice? Its not something that people normally think about.

[obermd]

The PCV valve is the controlling component in the system. It is a spring-loaded restriction in the vacuum path of the PCV system that keeps it from creating an uncontrolled vacuum leak. Manifold vacuum is pulled through the crankcase from a tube connected to the air cleaner housing to provide fresh, filtered air. In a properly operating engine, the amount of oil vapor is minimal and will easily blend and burn with the intake manifold air without leaving massive oil deposits as some people perceive. The PCV system performs two main functions. First, it draws piston blow-by gasses and oil outgassing vapors out of the crankcase to be burned. Second, by keeping the crankcase under a slight vacuum, oil leaks from other engine gaskets are kept to a minimum. Otherwise, positive pressure in the crankcase would force oil out through the gaskets over time.

How did you get "Gearhead" status without knowing engine basics?

I asked the same question when I was listed as one of the initial gearheads. The answer I got was that with my ability to see the entire car as a system of systems I can see the forest through the trees and come to the correct conclusion without knowing the details. I am very good at troubleshooting and finding root causes of issues, which is a hard learned skill that can be applied to cars even without initially knowing the details. Just gotta know what questions to ask and be able to correlate issues to figure out which ones are related and which are unrelated.

Thanks for the answer on what a PCV valve does. I'll remember this one.

[Starchy]

^^ Like a boss