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Wagner PCV valve

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Looking for input/comments/suggestions, particularly if you’re cammed up and turning lots of rpm.
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I installed mine this summer. I've never seen a product that was designed, made, packaged and documented with so much care. They obviously wanted it to be absolutely perfect. I installed it as a part of switching to a different (rebuild) carb, including tuning it, so I can't really tell how much difference it really made compared to the simple PCV valve, but I feel it was still worth the price.
 

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Of course, during "non-typical" driving, e.g. WOT (=typical for ArizonaGT as I understand it :)), there's no vacuum evacuation, since there's (almost) no vacuum at the source (the intake manifold plenum) and the ventilation just bleeds of the pressure.
 

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Well, actually there is. At WOT vacuum is low, but not absent. Bernoulli says that a low vacuum velocity is high and, at low vacuum, the PCV valve is wide open. Therefore you're going to move a fair amount (in volume) of crankcase vapors as opposed to when the throttle (and PCV) are near closed.
Sure, there is some vacuum, but very little, unless the carb is too small. And yes, the PCV valve opens up to compensate. But the discussion was about a reduction in leaks if the PCV system keeps the crankcase pressure below atmospheric. My comment to that was that at WOT there will be very little vacuum in the manifold and even less in the crankcase and thus the influence on leakage will also be very small. Especially considering the blowby will be higher due to the high cylinder pressures (even though the relative loss of the charge doesn't necessarily have to be worse)

BTW: Bernoulli says that pressure is reduced when velocity goes up.
 

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Bernoulli's Law applies whichever way you want to state that vacuum is inversely proportional to velocity.
Nope. Pressure is inversely proportional to velocity. Lower pressure means more vacuum. Like in the throat of a carburetor. The flow area is reduced, the air velocity increases and pressure in the throat decreases relative to surroundings (=vacuum). The higher the velocity, the more vacuum.
 

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Exactly, and VACUUM is simply NEGATIVE pressure. LOW vacuum, HIGH velocity.
Sorry for going of topic but when you say low vacuum, do you mean low pressure? To me, high vacuum is low pressure. Like tuning your idle screws for highest manifold vacuum = lowest pressure

I know I sound like a wise ass now, but negative pressure doesn't exist. I know what is meant and I used to say it too, until a teacher pointed out to me that it was wrong.
 

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I think this is more an "argument" about definition than about physics. Out of curiousity, when I would install an annular booster in a carburator that increases the air flow velocity through it, would you say that the vacuum at the suction hole(s) to the jets has gone up or down (i.e. more or less vacuum)
 

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OK, the annular booster was not the best example. How about an airplane wing: speed up the air on the top side, pressure on the top goes down, wing goes up.

About the rest, I know all that. But the discussion was about vacuum in the crankcase and how that helped with reducing oil leaks. I then said that effect will be very low at WOT, because there's very little manifold vacuum at WOT. Then you brought in the Bernoulli effect but in my opinion you mixed up high and low vacuum and how it correlates to air velocity.

But let's not dillute this topic any more with this side discussion ;)
 

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OK, I will respect the topic starter's wishes and will reluctantly resist the urge to fire back ;)

One last question though, just because I wonder what you mean:

At WOT, and with the PCV valve open wide, you're going to get the maximum amount of crankcase blow-by evacuated due to velocity, not vacuum.
What velocity do you mean, of the air flow through the throttle bores?
 

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Yes. The speed of the air, in feet per minute, times the volume of the air, in cubic feet, is going to equal "CFM" or Cubic Feet per Minute.

FWIW, not "mad" at all... maybe CRAZY but not mad. lol. Enjoy a theoretical discussion about hot air, when it doesn't involve politicians.
Well then, since Woodchuck enjoys it so much :D

Strictly speaking, speed of air [ft/min] x volume of air [cubic feet] = something in [ft^4/min] but I'm sure you meant speed of air [ft/min] x flow area [sq ft] = volume flow [CFM]

The flow through the PCV valve is a function of the flow area and the pressure difference over the valve. A high air flow velocity through the carb and manifold does not necessarily create a low pressure at the PCV valve exit. Unless it is positioned in a low pressure wake area, which is possible.


When people speak of negative pressure (or vacuum) they are speaking in relation to the datum of 1 atmosphere.

Until a few years ago there was no such thing as negative temperature (< 0 Kelvin). We use negative temps all the time due to where we set the datum.
I know, hence the "wise ass" comment ;)
 
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