I will be happy to tell you that there is more purpose to the PCV system than emissions only - and I won't be lying. As you know, PCV stands for positive crankcase ventilation. The purpose of this crankcase ventilation system is to....sit down for this one...ventilate the crankcase. Surely you know all about blow-by and how this pressures up the crankcase, do you not? I'm afraid theres alot more going on down in your crankcase than just "hot un-usable air." So that is why the system exists. Perhaps what you were trying to indicate is that the MANNER IN WHICH the system exists (how it functions) is for emission purposes only? Because you would be right about that. The only reason the gases (or hot un-usable air as you call it) are recycled into the engine rather than vented to atmosphere is an emissions reason. So by your logic a system is designed to reduce emissions, when you could completely eliminate the system and have no pollution at all, so why have the PCV system in the first place? I too miss the days when these gases were just vented to atmosphere and nobody cared.
Other cons of the PCV system is not only the "hot un-usable air" that it recirculates in the engine, but also pulling oil into the intake and less combustion effeciency.
