I'm not sure why it stops.blackcloud50 said:When the bowl starts to fill up but then stops, what exactly is the reasoning behind this? This is one of the reasons why the filter is removed, correct?
HISSIN50 said:I am with Kevin. The PCV valve and rubber lines are still the same size. The effective volume of the separator does not matter much at all (esp since it ends up being a restriction of sorts)..
Not sure I follow the analogy. Overcoming the gravity to suck the water up 3 stories would be more significant to me than the flow rate (absent gravity).352Ford2 said:Bigger the can the bigger the pressure drop, its just fluid mechanics. Same with increasing the length of the line, then you have a larger line drop.
think of it this way if you had a really long drinking straw, do you think you could sit on the top of a 3 story building and suck the water out of the swimming pool below?
I bet not
HISSIN50 said:There might be a slight lag that occurs while initially filling the catch can (additional volume, not unlike additional volume from running longer lines) but once it is up to speed, it wont matter. The restriction in the separator is what comes into play more than the volume IMHO. Fluid dynamics again.
So in the scheme of things, once again it doesnt matter if there even is some small pressure drop (I might have to go put a gauge on things to put this argument to bed - I postulate no meaningful vacuum reading delta with the separator vs without).
HISSIN50 said:Think of it this way. A cat converter is a larger diameter housing than the rest of the exhaust piping (2 1/4" or what have you). But there is not a pressure drop in the cat itself.
Apparently we dont see eachother's points, so we will have to let this one go.352Ford2 said:pressure is directly related to crosssectional area, if you go from 2" to 2.5 to 2" pipe, you will have the lowest pressure at the end of the last 2" pipe (pressure drop) highest pressure will be in the 2.5" pipe
go here at the bottom of the page is a anamation of Bernoulis Principle
it doesn't do a good modle of line drop, but it's still kinda neat.
http://home.earthlink.net/~mmc1919/venturi.html
HISSIN50 said:I still stand by my point that it makes no real world difference - probably because I have run each configuration. And running a large can is nothing new.
vristang said:Some good points.
My thought - If large volume separators reduced vac signal, then there would not be 1.5qt separators in use by so many race teams. The separators we are using are actually quite small.
However, I think the major influence on the ability of the pcv to work is the engine vac itself. The fact that there is no vac at wot and plenty of vac at idle bothers me. There is no vac signal when it is needed most, and plenty of vac when a vac signal is nearly useless. I realize that the pcv functions on the pressure differential between the crankcase and the intake, but this seems far from ideal to me.
jason
blackcloud50 said:Aren't those large volume separators for race teams used at the end of the vacuum source (like the vacuum pump would act like a pcv but pukes into the separator)?? This meaning that the separator is just a catch can really. Whereas the separator/catch can that would be inline between the pcv and upper is actually separating the aerated oil and not just used as a "puke can"
As far as the lack of pcv vacuum WOT vs. that under other driving conditions, that's one reason why there is a line running from the valve cover to the throttle body or inlet side of blower. Atleast that's my understanding of it.
Yes. I am interested as well. If you don't mind.HISSIN50 said:Jason, you know I am interested in these things.(if you dont post results, please shoot me a PM or email).
vristang said:I am not sure what you mean by the vac pump acting as a pcv? Can you elaborate?
I have heard this theory on why the tb/vc line is there. The theroy is that when the vac signal is weak the tb/vc line allows the crankcase pressure to vent. I am not sure I fully agree with this, and here's why.
I have had sufficient pressure build in the crankcase to blow the dipstick out of its tube (and by this I mean the dipstick hit the underside of the hood, and oil sprayed out of the tube). I have also had sufficient pressure build to blow out the rear seal on the lower intake. These 2 paths for crankcase pressure to vent are very high resistance paths compared to the resistance of the tb/vc line.
If venting crankcase pressure is a function of the tb/vc line, then it is a very poor design. As far as I can tell the tb/vc line is the inlet for fresh air entering the crankcase, and that is all it does.
I would love to hear others feed back on this.
jason
if we look at the fitting on the oil filler, rather than the TB, the answer is Both. THat smaller line does have a secondary benefit for allowing crankcase vapor to vent at WOT. However, its primary purpose is to work in concert with the primary line, since PCV flow is bi-directional. WIthout that smaller line, one could draw a vacuum in the crankcase and air would try and find its way into the motor through the seals (this smaller line is what allows the bi-directional flow to occur).blackcloud50 said:Quick question for anyone..If the tube on the throttle body (where the hose connects from the valve cover) was removed and left open, would air be coming out of the t/b or be drawn in?
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