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The much misunderstood PCV system:

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  1. #1
    Junior Member RevXtreme's Avatar
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    The much misunderstood PCV system:

    Understanding PCV Systems


    To understand why we need a proper PCV system one must understand what takes place in the crankcase during the average day of driving. First off, all internal combustion engines have a certain amount of "blow-by" or leakage past the piston rings into the crankcase. This consists of several compounds such as unburnt fuel and a small amount of the combustion gasses that result from the explosion of the air/fuel mixture. The combustion gasses contain several nasty things including sulfuric acid, carbon particles, and other caustic compounds that will contaminate the oil over time. In the crankcase there is also a certain amount of water, or moisture from condensation. Even if never run, an engine will accumulate moisture from the heat of the day to the coolness of the evening depending on how humid the climate is where the motor lives. Every time the motor gets run up to operating temperature these compounds are "gassed off" and with the OEM system it all gets "flushed" or pulled into the intake manifold where it is mixed with the intake air charge and burned in the combustion process and further in the catalytic converter before it is exhausted into the air as mostly just water vapor at that time. Now of course, a small amount keeps leaking past the rings into the crankcase and completes the cycle all over again, but without a proper vacuum pulled ventilation system....these nasty compounds will break down the oil and reduce its protection properties and the corrosive aspects start to rust internal parts resulting in reduced engine life.
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    In the "old days" of our grandfathers, the engineers that designed engines new the importance of evacuating these nasty compounds and the design was extremely simple. First was nothing more than plain breathers to allow excess crankcase pressure to be released or vented. But the damage from not "flushing" all the gasses out resulted in very short engine life (of course the oils of that day were nothing like the protection today's synthetics provide) so the next change added a vent tube, or evacuation tube that ran from the top of the crankcase to low on the car where the air streaming past would create a suction, or vacuum that would pull the vapors out and vent them directly into the air with a breather (barely filtered with a wire mesh type media that was oiled to catch dust & dirt) allowing the "fresh" makeup air in to complete the flushing process. Now this resulted in greatly increased engine life, but as the motors got worn oil would start to drip out the tube and drip onto the roadways, then the rain would wash it into the ditches, where it would enter the ground water (you know the rest of the EPA story) and the gasses just vented to the air.
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    As the EPA and the powers that be mandated stricter emission laws the system was refined more and more ultimately evolving into what we have today. A completely sealed system that uses the vacuum provided by the intake manifold to draw these vapors out, and the filtered fresh makeup air is drawn from the main air intake system and filtered by the main air filter. This results in very clean emissions, but the unintended issues are the detonation or "knock" that occurs when oil is introduced into the combustion chamber that the knock sensors pick up (before we*can hear it)*and pull timing to protect the engine from damage, and thus reduced power. Another result is the carbon buildup on the valves & piston tops (any techs reading this can surely verify the amount) also resulting in decreased performance and less power made.
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    The purpose of a proper oil separating catch can is to route these gasses through a baffle system that provides the most contact possible with the outer surface resulting in the oil being trapped and removed from the other gasses that do continue on through the intake and are burnt and consumed. It does NOTHING else in ANY way to the engine oil itself....it can't.
    *
    Deleting your PCV system:

    While this will insure NO oil the the intake tract via the PCV, it will greatly shorten the life of your engine if street driven. The worst example I have seen is to cap off all the fittings and run an open hose from each valve cover to near the ground. One would think “they are both releasing pressure, so what can it hurt”. The answer is plenty. Lets take the basic principle of the Venturi effect. Whip a piece of hose around in a circle so that air rushes past the end. This will result in suction from the end of the hose near the center of the radius. Now with a car traveling down the road at speed, both hose will have air traveling past the ends and one ultimately will have more air rushing past thus creating more suction, and the other will them become a vacuum tube sucking up dust, dirt, water, sand, etc. directly into the engine from the side with the least suction. Depending on the amount of dust & dirt on the roads you travel (just look under your hood to see all the sand & dust that accumulates on the engine exterior). So it may take years to destroy your engine this way, or it may take no time at all. To see this if you have been misguided into doing this just remove each valve cover, and looking up into the baffle in each you will see the accumulated dirt built up as it comes in contact with the oil.

    Now, addressing the "Home Depot" oil separator, it will and does catch a small amount of the oil but the majority still gets past into the intake (we used these and then the other cans that popped up on the market through the years before designing the ultimate final product that is offered today) and the reasons are simple:
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    It is plastic and transfers heat very inefficiently so very little condensing takes place.
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    The size. Anything less than 1 qt capacity and there is not enough surface area to be as functional.
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    And the lack of an effective baffle system allow oil to be pulled directly through.
    *
    As for having steel wool or another type of filter media inside, this will work well at first to trap oil....but as soon as it gets saturated droplets are pulled off and into the intake.
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    Why don't the auto manufacturers incorporate something similar? Cost and the added maintenance was deemed something that would NOT be accepted by the general market. (even though it is as simple as draining the can at each oil change).

    The RevXtreme oil separating can is the best functioning can on the market and is easy to test against any other. Simply install a clear inline fuel filter between the outlet of any can & the intake manifold, you will see some saturation of the filter element with most any other, and as long as long as there are not internal engine issues, the RevX can will show little if any getting through, as it has a unique design with a perforated dispersion tube running down the center of the can from the inlet that results in the most complete dispersal possible for condensing the vapor/mist to droplets where it is trapped to be drained later. What makes the RevXtreme can even better is additional internal baffling consisting of discs that channel the exiting gasses one last time along the outer surface before entering a separate channel that keeps the trapped oil in the main portion of the can and a integrated PCV check valve that controls the amount of vacuum pulled and prevents "back-flow" or reversion back to the crankcase.
    *
    Bottom line is this: The OEM system does a great job of meeting emission standards and removing the harmful contaminants, but the unintended consequences are the oil that is drawn into the intake charge. For an engine to produce the maximum amount of energy per explosion (of the A/F in the combustion chamber) you want air & fuel only....any amount of oil in this mix will hamper the explosion resulting in less energy released, detonation, and carbon buildup. Trapping and removing this oil before it gets into the combustion chamber is the ONLY solution to maintaining the maximum efficiency and prevent excess carbon buildup.

  2. #2
    Senior Member Z28boy2000's Avatar
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    interesting read

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    Member SS201's Avatar
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    interesting indeed, what does the revextreme can look like?

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    Veteran 0rion's Avatar
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    sarge already has a pcv write up
    PCV/Catch Can/Crank Pressure


    isn't your infraction due to you coming on here and bashing revextreme and saying what crooks they are? Now you're their top salesman?

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    O U 8 1 2 Spaz's Avatar
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    Quote Originally Posted by 0rion View Post
    sarge already has a pcv write up
    PCV/Catch Can/Crank Pressure


    isn't your infraction due to you coming on here and bashing revextreme and saying what crooks they are? Now you're their top salesman?
    yup... it's like a drama tv show... the more drama and bull shit the more viewers it gets...

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    Member c5z28's Avatar
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    On your ass flashing
    my highbeams


  7. #7
    Veteran 0rion's Avatar
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    this thread is older than that one.....guessing they had a falling out. Thread done.

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