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valve cover breather hose

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bensenvill

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Sorry if this is going to come off as a noob question, I'm just trying to get a better understanding.

So I've seen alot of cars with little cone filters on the valve cover rather than hose run to the intake.
Is this safe to do with our cars?
 
sorry perhaps I was unclear, I'm talking about replacing the hose with a little valve cover filter, and plugging the hole in the intake tube. That would not cause unmetered air. I'm just trying to get a better understanding of the function of that hose. Like which direction the air is flowing, is it flowing into the valve cover or out, would I be compromising any function of the car by doing it?
 
bensenvill said:
sorry perhaps I was unclear, I'm talking about replacing the hose with a little valve cover filter, and plugging the hole in the intake tube. That would not cause unmetered air. I'm just trying to get a better understanding of the function of that hose. Like which direction the air is flowing, is it flowing into the valve cover or out, would I be compromising any function of the car by doing it?
Click to expand...

Air is flowing from the valve cover to the intake. If you have a crankcase breather on the valve cover, air will escape through the filter and bypass the accordian tube. As you can see, this air is entered AFTER the MAF unlike air which is drawn through the main intake filter. As a result, the MAF already takes this metered air into account since its not directly metered. Bypassing it is not a good thing.
 
i dont understand why you would want to do that in the first place? whats wrong with your setup now?
 
Black 98 CSVT said:
i dont understand why you would want to do that in the first place? whats wrong with your setup now?
Click to expand...

I'm not looking to do anything, once again, it was just to gain understanding of the process [although ideally it would be nice to eliminate just to have a cleaner looking engine bay... 2 less visible hoses].

beyondloaded, thanks thats the description I was looking for. I'll ask my tuner if this is something that can be reliably compensated for in software.
 
The main reason you don't want to do that is that it shortens engine life. Positive Crankcase Ventilation was a huge improvement when it became common to meet early smog requirements in the early 60's. I wouldn't do away with PCV on a racing engine either.

For racing only applications, an alternative is to vent the crankcase through the exhaust. It requires the use of a check valve to prevent pressurizing the crankcase from exhaust pressure. The exhaust is full of positive and negative pressure pressures as it pulses from the opening and closing of exhaust valves. With a proper check valve a very strong crankcase ventilation takes place, especially when the engine revs are high. That's when you need intake filters on the valve covers.

For street use, even high performance street use, forgetaboutit.
 
isn't it negative crankcase ventilation [since its sucking air out rather than pushing it in]?

interesting about going through the exhaust [would never consider that]. Getting deeper into the requirements, both the draw through the intake and push through the exhaust are RPM based, so the CFM varies depending on workload... Is that a necissary function to be varied over workload or say _hypothetically_ vent it to the atmosphere using some venturie style tube in the airstream of the cars underbody [assuming its designed to be efficient within a certain operating speed range].

don't worry about me doing anything dumb with my car, at best its a dumb toy that gets driven around the block once a month.
 
PCV stands for Positive Crankcase Ventilation. I think the name comes from a non positive system used prior to PCV, known as a road draft tube. It was a tube hanging under the car connected to the crankcase (usually at the valley cover, below the intake manifold on a V8). It allowed ventilation when the car was not moving, but only from the ring blow-by pressure. Positive ventilation was not effective under about 15 to 25 MPH. It became effective when the "road draft" was strong enough to pull the fumes out.

The current closed PCV system is much more effective. I would agree that it would be even better if greater effort were made to better separate or baffle the liquid oil that is carried with the blow-by fumes.
 
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