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103 Posts
Or why you don't need a catch can (or two).
During engine idle there is a huge vacuum in the intake manifold, less and less vacuum as the throttle plate opens more and more("A"), until at WOT the BOOST comes into play and the intake manifold begins going positive with respect to atmospheric pressure("B").
A.) The reverse flow prevention check valve remains open as long as the pressure on the crankcase side is higher than the intake manifold. So the airflow path is from the air hose connection just downstream of the engine air filter (filtered air), through the engine crankcase and then out the check valve and into the intake manifold, subsequently entering the combustion chamber and being burned.
B.) If/when/once the onset of boost results in the intake manifold pressure going positive with respect to the crankcase pressure the check valve closes blocking any flow into the intake manifold from the crankcase. Now, any blowby that would otherwise pressurize the crankcase simply flows out what was the inlet path/hose, through the turbo impeller, CAC, and enters the intake manifold etc, etc.
The engineering design theory being that if the crankcase gasses (etc.) are continuously evacuated in the manner there will never be enough gas/oil/water/etc. entering the combustion chamber all at one time to adversely affect the engine operation.
During engine idle there is a huge vacuum in the intake manifold, less and less vacuum as the throttle plate opens more and more("A"), until at WOT the BOOST comes into play and the intake manifold begins going positive with respect to atmospheric pressure("B").
A.) The reverse flow prevention check valve remains open as long as the pressure on the crankcase side is higher than the intake manifold. So the airflow path is from the air hose connection just downstream of the engine air filter (filtered air), through the engine crankcase and then out the check valve and into the intake manifold, subsequently entering the combustion chamber and being burned.
B.) If/when/once the onset of boost results in the intake manifold pressure going positive with respect to the crankcase pressure the check valve closes blocking any flow into the intake manifold from the crankcase. Now, any blowby that would otherwise pressurize the crankcase simply flows out what was the inlet path/hose, through the turbo impeller, CAC, and enters the intake manifold etc, etc.
The engineering design theory being that if the crankcase gasses (etc.) are continuously evacuated in the manner there will never be enough gas/oil/water/etc. entering the combustion chamber all at one time to adversely affect the engine operation.