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naoaki naoaki is offline
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Posts: 151
Join Date: Feb 2016
Car: 335i
Default 04-27-2020, 02:30 PM

Originally Posted by Rob@RBTurbo
The "high side" flapper is actually dual purpose.

It closes under low load to allow small vacuum to be placed on the crankcase, and with the built-in orifice it allows clean filtrated air (ie. from the air filter rear inlet) to replenish the crankcase environment for "positive crankcase ventilation".

Then under high load it opens and basically does nothing aside for gets out of the way for forced ventilation with some small "vacuum" aid from the rear inlet.

You want to retain the flapper on the high side as long as you are retaining the PCV valve as part of your system.

Too many people over complicate this system by adding in too many parts they see available online, and wind up with some hodgepodge of a system that just doesn't work properly. Keep it simple out there guys, there is not too much that is needed to be done here for nearly everyone.

Thank you for your explanation. I came to the same idea. Factory flappers are important in PCV systems. I added a check valve in the middle with the VTA system, but it does not seem to have the same effect as the factory flapper. This time I learned a lot about the PCV system.

BMW 2007 E90 335i
JB4 G5 IOS MHD race flash MMP High flow aluminum intake MMP Hot side inlet Down pipe Outside intercooler Twin oil cooler cp-e charge pipe BMS meth kit turbo lab stage 1 turbo CSF radiator fuel-it stage 1 pump
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