it must be true because its on youtube.
whats that, you agree?
man i have never heard such a load of uninformed nonsense in my life.
none of these people seem to understand what is causing oil vapors to collect in the intake tract in various places.
PCV systems work in two ways, first the PCV valve, this is only open when there is a vacuum in the intake sufficient to pull the valve open and if not it will be closed. the second way is as a flash arrestor to prevent an explosion in the intake from traveling back to the crankcase and igniting vapors that may be present.
in addition to this PCV line, most if not all engines must have a way of supplying additional air to the crankcase so that flow can occur like a valve cover vent, this will allow the PCV pipe to remove vapors and replace them with fresh air.
modern engines use a system called make up air, this is a system that draws air from the inlet tract upstream of the throttle body, on speed density engines this is drawn from the air box on the down stream side of the filter giving clean air to the system. on MAF engines it is installed in the intake tract down stream of the MAF but upstream of the throttle body so that the MAF sees this air and can fuel the engine accordingly, speed density uses the fuel tables to compensate for this in conjunction with the MAP sensor.
here is where we run into a problem, what happens if the throttle is opened wide? well the PCV shuts so air flow through the crank case stops.
unfortunately turbulence in the crankcase does not and blow by is present, these two things are present in all engines but there is no way to remove them.
in a speed density engine this blow by together with oil vapors present in the crankcase find the least path of resistance to escape which is the pipe for make up air sending the pressure and oil vapors to the filter box, as we are at WOT the pressure in the box is below atmosphere due to the draw of the engine, no vacuum but flow is present so the vapors and gasses are drawn through the intake tract to the engine.
in a MAF system a similar situation applies but the crankcase is vented into the runner where it is again sucked into the engine, the problem is how much of this is air, as everything that gets into the engine has been metered including make up air, but now we are in a state where make up air does not exist.
no make up air equals no flow through the crankcase, so where is all the pressure coming from? answer, blow by.
is this good or bad, the reasons for blow by in a good engine as opposed to one that is worn out can be defined in one term, ring seal, in modern engines piston rings have had their tension reduced due to fuel economy over parasitical losses and now we are teetering on the edge of a blow by cliff, to push us over the edge is the ever present danger of crankcase pressure, this has a detrimental effect on ring seal due to the narrow nature of these low tension rings causing flutter.
well that's it then we are screwed and every time we hit a WOT the pressure rises forcing the creature from the black lagoon into our intake and oil to spew from every orifice.
well not quite, if we can do something about crankcase pressure at WOT, if we vent the crankcase to atmosphere with suitably large vents, i revert back to a time in the distant past when i ran a triumph twin on fuel and a blower, a blow by nightmare if ever there was due to the windage of two pistons going up and down together combined with the quantities of fuel and a blower raising the combustion pressure, nitro is an oxygen rich fuel requiring virtually no air to keep the motor running at idle, on a 750cc engine we would run a breather to atmosphere of 1-1/2"" diameter and still place it opposite the magneto to stop oil passing the seal, this would maintain crankcase pressure to atmospheric.
so you can see that to vent a car engine to atmosphere would require a lot of ventilation if it was predisposed to blow by by design.
so to recap as you can get lost in all of this, BAD blow by bad, oil in the intake causing unstable mixtures bad, oil leaks past seals bad, oil in the combustion chamber causing detonation bad, oil on the intake valves bad, oil on the throttle plates bad and crankcase gasses in the intake charge taking the place of air GOOD high crankcase pressure helping the oil pump to lift oil from the pan good oil vapors wizzing around in the crankcase to lubricate the wrist pins good, oil lubricating timing chains good
this brings us to the real story, we need oil vapor in the crankcase, we need oil that can absorb the contaminants of blow by without degrading between oil changes, we need a good filtration system to remove particulates of combustion, what we don't need is the oil escaping from the crankcase in the form of vapor, we need a slight vacuum in the crankcase to promote ring seal and to reduce oil leaks and no atmospheric breathers throwing oil all over the place.
VAC-U-PAN, via closed oil breathers on the valve covers connected to a check valve/flame arrestor which in turn is placed in the exhaust to extract the gasses and any vapors that are not captured by the breathers, alas these only seem to work with open headers as you can't expect them to suck if there is back pressure in the exhaust due to mufflers or cats, on race cars o.k. i have used them with success.
so catch cans i here you say vented to atmosphere, this would help some but you only get atmospheric at the best in the crankcase and we need a negative pressure for ring seal.
this leaves us but one option, we must suck the pressure out of the crankcase via a catch can which drains the oil back to the pan where the remaining oil can absorb the included contaminants. and vent the gasses extracted to atmosphere, the only thing to worry about is what oil and how long will it last between oil changes.
_________________ this story shall the good man teach his son, and chrispin chrispian shall ne'er go by, from this day to the end of the world. but we in it shall be remembered.
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