Actually, you got me.....with that word adsorbent - I have never ever seen that word B4, in my entire life - or, if I had, prolly tho't it was misspelled then, also - bummer! Good word to describe K&N function - meaning adhering without absorption = adsorbent
Prollem being, crankcase effluent is under some pressure, is very hot, is sooty oil-laden (or oily soot-laden), and is also at some volume greater than could be handled by a small inline filter\rejector\drain-backer* - note the size of the outlet hose - that volume increases as engine works harder and gets hotter due to increased power demand - soot particles can be larger during over-fueling at minimial air\fuel ratio, smaller as air\fuel ratio increases, but the output volume of the crankcase does not remain at some small, steady volume - thus the cylindrical volume of the Provent and such, required to 'filter' the effluent volume without being or becoming restrictive to that effluent - Provent and Racor maintenance intervals are based on engine displacement and useage\service
*If you have not, checkout the alphabet soup thread in CRD TECH section, see how the CCV puck is constructed to be a primary centrifugal filter with pressure and vacuum venting - inside the valve cover is a synthetic mesh coalescing pre-filter, both of which are designed to remove most of the oil mist from crankcase effluent vapors, some of which is due to oil evaporation at TurboDiesel temperatures, and both of which are designed to handle large volume effluent
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