Valve cover vent tube......

Topic: Valve cover vent tube...... (Read 8731 times) previous topic - next topic

Valve cover vent tube......

Reply #30 – January 28, 2013, 02:35:26 PM

1WLD BRD
wrong, the air is sucked OUT of the valve cover and into the throttle body.

NOPE^^^

The PCV sucks in the fumes under vacuum and it draws through the filtered hose from the valve covers to the PCV. Simple to test just put your finger on the PCV valve and notice it pulls in vacuum. Closed systems are federally mandated. As for Pressurized engines go. You need a check valve in the PCV system to prevent pressurizing the crankcase under boost. Leaving the hose off the intake portion will cause un metered air to enter the engine and drive it LEAN. This is of course if it is behind the air flow metering device.

Valve cover vent tube......

Reply #31 – January 28, 2013, 02:42:51 PM

Quote Originally Posted by softtouch View Post
Yep. That is how it works. Air goes in through the valve cover and out the through the PCV.

Correct This is exactly how it works. It is called a closed crankcase system. Or CCS

Valve cover vent tube......

Reply #32 – January 28, 2013, 07:48:57 PM

Quote from: softtouch;408259

I don't know about super charged or turbo systems, but that is not what we are talking about. If the intake is pressurized I can see
So the BS is flowing from Dunnville, along with the cold air.

drum roll and ......3,,,,,,,,,2,,,,,,,,,1 : )

Valve cover vent tube......

Reply #33 – January 28, 2013, 07:53:44 PM

is it possible that the flow in the tube either reverses or goes stagnant so to speak when at higher rpms? when the pcv is not fully open ?

Valve cover vent tube......

Reply #34 – January 28, 2013, 08:24:06 PM

Jay @WOT when vacuum is low Blow by is basically in limbo. It goes to the least resistance. That is why the intake plenum gums up on blow by motors. But this is for a brief time till vacuum returns. If you see a car on a dyne it can easily be seen. A fresh engine has very low Blow by. Basically reversion is at a minimum. Other than pressurized engines if the check valve fails. When a check valve fails bad things happen. Boost is introduced in to the crankcase and blows oil out of every nook and cranny. That is how the dip stick blows out of the stick tube.

Valve cover vent tube......

Reply #35 – January 28, 2013, 08:26:35 PM

But the PCV still draws FROM the crankcase, most commonly via a hose, or some sort of fitting on the valve cover.

When I first started driving my '74 J10 (Jeep truck, when AMC ran the show) some old drunk had ran the PCV hose from the valve cover into the oil fill tube. It kept blowing the dipstick out of it's tube, and while I enjoyed the rust protection on the bottom of the hood and the inner fenders, it wasn't until I got a Chilton manual that I seen it needed to run from the fill tube to the air cleaner.

I'd roughly say that whether it vents from the oil fill, directly from a fitting on the valve cover, if there isn't a baffle to keep oil from getting sucked up into it, you are going to have a big mess in a short time.

As for whether the air from the crankcase is sucked, drawn, pushed, or however you wish to term it, simple fact is that the engine draws it in by vacuum. At least it did on my old J truck. I'd imagine that there are different methods, technology and ways to do the same thing via a little different method.
It's also possible that the EEC of say, a Mustang, with a Mass Air system is calibrated for that small amount of airflow coming from the crankcase so that there are no ill effects. It's also possible that this amount of air isn't so great as to even be a worry in a properly maintained system.

And since a Mass Air meter only measure a little stream of the air real time, any changes to the air pressure would immediately be compensated for, via the readings from the 02's, the TPS, and where the throttle is set at, as well as engine RPM.

Of course, I could just be full of shiznit, but according to a few sources, not so much.

Valve cover vent tube......

Reply #36 – January 28, 2013, 08:30:32 PM

As for saying that anything that that has vacuum that doesn't first run through the Mass meter is silly. What about the EGR? The cruise servo? The network of lines for the heater controls? All the hoses on the bottom of the intake, and yes, even the brake booster?

Now if a system is sealed, there's obviously no leak, no unmetered air flowing in, well, not very MUCH. I bet it wouldn't be any more than what is drawn through a PCV valve...food for thought.

Valve cover vent tube......

Reply #37 – January 28, 2013, 08:43:46 PM

Pull A dipstick out of a BMW and see what happens. Different manufacturers use different systems. Bottom line is the crankcase is under a vacuum . The PCV sucks in the blow by fumes and the intake portion is from the valve covers most of the time. Having a working PCV and a valve cover breather is fine. When the PCV system gets overloaded and it does(THAT IS WHY I USE 2 PCV VALVES ON CERTAIN ENGINES) You get reversion. Then the intake sludge's up as the flow reverses on loose engines. (BAD RINGS) To much blow by. But with the feds designing emission regs the systen is a closed one to minimize emissions.

Some use CATCH CANS to recover the oil as the system gets overloaded. Or use a crankcase pump for evacuation.

Valve cover vent tube......

Reply #38 – January 28, 2013, 08:52:55 PM

learned me a new word,, reversion. i just might use that one.
so reading your instructons twice, i read into it that the flow can reverse and its briefly happening. i wish i had used the term briefly because thats what i meant by during the times when at higher R's, and the pcv is not fully open.

Valve cover vent tube......

Reply #39 – January 28, 2013, 08:57:36 PM

learned me a new word,, reversion. i just might use that one.
so reading your instructons twice, i read into it that the flow can reverse and its briefly happening???????? regardless of motor condition but most obvious on a blow by motor>?

Valve cover vent tube......

Reply #40 – January 29, 2013, 03:03:23 AM

Tom, great info. You still haven't adressed the air going into the breather and coming out of the PCV is unmetered. That is the only reason I have not chimed in. I have no answer to that. I do believe you are correct in saying he can get by with a PCV on one side and a breather on the other, I just can't get past the unmetered air thing. Doesen't all incoming air have to be metered? Not meaning to hyjack here, but I am interested in your mention of using 2 PCV valves. One on each side? My truck has a blow-by issue. Later I would like to do an engine swap to fix it and get more power, but for now I need to keep the oil in the engine and out of the intake. PCV valves only allow air to flow through and not oil, am I correct?

Valve cover vent tube......

Reply #41 – January 29, 2013, 06:18:42 AM

Yes and no Chrome anything that allows un-metered air to enter after the metering device is UN - Metered by that device. Example if you have a ripped boot after a Mass air flow meter to the throttle plates the car will set a lean code. If you have an air leak before the metering device like a ripped boot from the air cleaner to the metering device it does not matter. That air entering the metering device is measured. If a leak after the metering device is tuned in to the system it is OK. Example a PCV VALVE is a designed vacuum leak after the metering device. So basically when the crankcase is under vacuum from the PCV VALVE hydrocarbons are sucked in to the intake. When under WOT the incoming air across the throttle body sucks those Hydrocarbons from the mentioned tube. Another words a venturi action from incoming air pulls in those fumes from the tube. Or which one has the upper hand at the time. This is why the throttle body needs cleaning as the incoming Hydrocarbons and oil film coat the throttle blades. This also happens from reversion in the crankcase. Thanks

Valve cover vent tube......

Reply #42 – January 29, 2013, 06:47:52 AM

Quote from: TOM Renzo;408334

Yes and no Chrome anything that allows un-metered air to enter after the metering device is UN - Metered by that device. Example if you have a ripped boot after a Mass air flow meter to the throttle plates the car will set a lean code. If you have an air leak before the metering device like a ripped boot from the air cleaner to the metering device it does not matter. That air entering the metering device is measured. If a leak after the metering device is tuned in to the system it is OK. Example a PCV VALVE is a designed vacuum leak after the metering device. So basically when the crankcase is under vacuum from the PCV VALVE hydrocarbons are sucked in to the intake. When under WOT the incoming air across the throttle body sucks those Hydrocarbons from the mentioned tube. Another words a venturi action from incoming air pulls in those fumes from the tube. Or which one has the upper hand at the time. This is why the throttle body needs cleaning as the incoming Hydrocarbons and oil film coat the throttle blades. This also happens from reversion in the crankcase. Thanks

So, what you are saying is, with a breather, what little un-metered air comes from the PCV is not enough to cause a problem. Ford antited a little bit of un-metered air to be sucked into the engine. In-perfect for a reason.

Valve cover vent tube......

Reply #43 – January 29, 2013, 07:00:57 AM

Just an added note. Any air entering the engine must be filtered, or else unwanted debris will go in as well. Breathers are filters and must be cleaned on occasion.

Valve cover vent tube......

Reply #44 – January 29, 2013, 11:23:10 PM

humm, i would venture the EGR could argue with you,, it provides its offerings to the intake without descrimination of what just poped out,, lol.