How is a PCV Valve rated?

[jamyers]

I was Dogpiling this topic, and came up with this tidbit. Unfortunately I closed out the window (site) I got it from, iirc it was 'nastyz28.com or something like that.

1. Test Procedure and Criteria
a. Measure the flow of the PCV valve in standard cubic feet per
minute (SCFM) vs. pressure differential across the valve over a range of
operating pressures from 4-22 inches Hg., at standard atmospheric
conditions (21.1 [deg]C (70 [deg]F) at 755mm (29.92 inches).

 

[BIGREDRASA]

OK, James, that looks like half a football score. Nebraska 38.....

 

[rmt]

...I may just play with one using a vacuum gauge teed into a hose, with a little shutoff valve inline with the intake manifold. Intersted in seeing what the gauge and observation of the poppet tell me.

One of the neat things the PCV valve does is hover at certain vacuum levels, somewhere in between the two extremes to match vacuum level and therefore engine speed. A finely tuned balancing act between the weight of the "jiggle pin", the strength of the spring, and the size and shape of the jiggle pin and of the corresponding holes in the valve at each end of it.

PCV valves don't get the credit they deserve.

 

[66 Fastback]

This whole thing makes me wonder about an old company car, '84 Chevy Celebrity I drove for a few months in the 80's. I was working as a Drilling Foreman on dusty roads up in Michigan. The air filter constantly clogged up from all the blowby and dust that caked the filter. I had to beat the dirt out of the filter a couple of times a day. The previous foreman had told me he got the engine hot a few times fording through some mud, of course those 13" wheels did not help that situation. But I wonder if the engine just had a plugged PCV valve rather than being worn out and abused. I ended up parking it and renting a truck after the exhaust system fell off at the header pipe and I had to drive back to the office in reverse to keep from plowing a ditch in the road while going forward.
Doug

 

[rmt]

Perhaps a sense of wonder has appeared here?

Sense of wonder ... the understanding that there is something that one had not fully comprehended — or perhaps had not even recognized that there was something to be comprehended — until that point.

Mostly attributed to science fiction writing, but something I ran across a while back that I can't seem to get out of my head. I try to stay aware of it for myself now, because usually when it comes it involves some sort of enlightenment. Usually a good thing, but I suppose it may not always be.

(Hey, I get it now! That sucks! Still, better to know something than not. I guess. Most of the time. Maybe. There are things you might be better off not knowing. Possibly.)

Roger

 

[BIGREDRASA]

Hmmm! It appears that we are at the mercy of the parts catalog. Whatever number is called for, we use and hope. Which throws another curve into the question. What about the Ch-1-na branded products?

I just put in a Motorcraft valve I had in the garage, and it doesn't rattle. Maybe it will work, maybe not. The poppet had "AA" on it. Only thing is that I don't know for sure which of my vehicles, past and present, it was designed for.

 

[jamyers]

Anybody got a flow bench and a free Saturday afternoon? I'd contribute $20 to the beverage-and-pcv-valve fund...it'd be interesting to get some specs on 5-10 of our older pcv valves.

Tony - just LOOK at the can o' worms you opened up!!!

 

[Bort62]

Anybody got a flow bench and a free Saturday afternoon? I'd contribute $20 to the beverage-and-pcv-valve fund...it'd be interesting to get some specs on 5-10 of our older pcv valves.

Tony - just LOOK at the can o' worms you opened up!!!

A vacuum and a differential pressure transducer would suffice.

 

[wsa111]

I don't know the design critera is as far as orifice is but i'm sure it is directly proportional to the displacement of the engine.

Small engine small orifice, large engine large orifice.

I would match the valve to the size engine you have & then you will close.

I would use the valve recommended by the manufacturer.

The valve that really threw me a curve is the 2 way valve used in my supercharged lightning. Thats another story in itself & i will not go there. Bill

 

[BIGREDRASA]

Anybody got a flow bench and a free Saturday afternoon? I'd contribute $20 to the beverage-and-pcv-valve fund...it'd be interesting to get some specs on 5-10 of our older pcv valves.

Tony - just LOOK at the can o' worms you opened up!!!

A vacuum and a differential pressure transducer would suffice.

Hey, you're pretty smart! A nice ShopVac would pull all the vacuum I'd ever need. The wand has a bypass hole that allows the suction to be controlled.

Now, anybody have a pressure transducer lying around?

 

[Stubby]

Two MAP sensors with my Innovate LMA3 might do the trick. Right now my LM1 is in Colorado. You could also use manometers, if you had access. I would imagine most guys who own a small flow bench would let you use it on return for the info gained.

 

[jamyers]

A vacuum and a differential pressure transducer would suffice.

Umm...my first thought was something snarky like: "Sure, Bort - if I don't have a flowbench, why would I have a differential pressure transducer?" (whatever that is) :roll: :mrgreen:

Then I read on and realized that if a MAP sensor be one of those thingies, then I've got several in a box here someplace. Now, figgering out how to rig it all together in a meaningful way....

Like I said, I'll donate to whoever wants / knows how to answer RASA's original question.

 

[XPC66]

Just a pitot tube and magnehelic would suffice. I was going to use one of my hot wire anemometers with an electronic manometer measuring drop across the valve for the hell of it.

A vacuum is not necessarily req'd ... you could put something like dry nitrogen through it instead. A vacuum is already at hand on the engine manifold.

Actual PCV valve testing involves plotting 20 Delta points between 1"hg and 20"hg, Flows vary between 0.1 l/s upto 3.75l/s between valves.

 

[XPC66]

Hers an interesting back to the future article :

http://www.mightyautoparts.com/pdf/articles/tt122.pdf

 

[Bort62]

Anybody got a flow bench and a free Saturday afternoon? I'd contribute $20 to the beverage-and-pcv-valve fund...it'd be interesting to get some specs on 5-10 of our older pcv valves.

Tony - just LOOK at the can o' worms you opened up!!!

A vacuum and a differential pressure transducer would suffice.

Hey, you're pretty smart! A nice ShopVac would pull all the vacuum I'd ever need. The wand has a bypass hole that allows the suction to be controlled.

Now, anybody have a pressure transducer lying around?

I think I have a diff pressure transducer, but its 0-100 PSI so that's not going to do any good.

They aren't terribly expensive.

 

[Bort62]

Two MAP sensors with my Innovate LMA3 might do the trick. Right now my LM1 is in Colorado. You could also use manometers, if you had access. I would imagine most guys who own a small flow bench would let you use it on return for the info gained.

Well, I would be skeptical of the accuracy and precision of off-the shelf MAP sensors.

But yes, they are pressure transducers. You would need a 2 bar MAP for this application (or one with a reference port). Alternatively, you could have the "downstream" be vented to atmosphere, in which case a single transducer would work. Again, a 2 bar MAP would be needed.

Hell, one could just use a gauge. Data logging Via Pencil & Paper.

A constant flow source (vacuum) + differential pressure transducer will tell you which valve flows more, but it won't tell you what it is flowing.

In that case, a flow meter is needed. A hot wire anemometer would work fine given some way to calibrate it.

I have a USB DAS that is perfect for this, no need to screw with weird data logging techniques. However, if someone else were to do this, a simple boost gauge would work pretty good.

Especially if you had some way to calibrate it.

 

[BIGREDRASA]

Hers an interesting back to the future article :

http://www.mightyautoparts.com/pdf/articles/tt122.pdf

The plot thickens!

Although one approach would be to say X valve for Y displacement, I suspect that changes such as timing, carbs, FI, headers, etc. would affect the PCV performance/requirements. That tiny fixed orifice unit GM retrofitted is something to think about.

 

[Stubby]

Two MAP sensors with my Innovate LMA3 might do the trick. Right now my LM1 is in Colorado. You could also use manometers, if you had access. I would imagine most guys who own a small flow bench would let you use it on return for the info gained.

Well, I would be skeptical of the accuracy and precision of off-the shelf MAP sensors.

But yes, they are pressure transducers. You would need a 2 bar MAP for this application (or one with a reference port). Alternatively, you could have the "downstream" be vented to atmosphere, in which case a single transducer would work. Again, a 2 bar MAP would be needed.

Hell, one could just use a gauge. Data logging Via Pencil & Paper.

A constant flow source (vacuum) + differential pressure transducer will tell you which valve flows more, but it won't tell you what it is flowing.

In that case, a flow meter is needed. A hot wire anemometer would work fine given some way to calibrate it.

I have a USB DAS that is perfect for this, no need to screw with weird data logging techniques. However, if someone else were to do this, a simple boost gauge would work pretty good.

Especially if you had some way to calibrate it.

I was thinking about checking with vacuum. It sounds like you are talking about useing pressure.
I have pressure transducers at work that will measure with extreme accuracy. I just don't think I could convince the boss that I need to use a 15,000 dollar transducer for checking PCV valves.

After reading again, I was thinking you talking pressure because the 2BAR MAP is used for boosted applications mostly.

You wouldn't have to know exactly what it flows, as long as you get a good comparison of the differentials.

 

[rmt]

I'm thinking trial and error is looking pretty good.

 

[Anonymous]

My vacuum readings are slightly lower than they were with the 1100. Since I installed the HW5200 with adapter, my PCV Valve makes a rattling noise and I get fluctuations in my vacuum.

Is your valve a plastic or metal one? The metal ones are usually a lot more "noisy" than the plastic ones.

Later,

Doug