Closed loop is not quite right, more of a closed crankcase. The system has to pull air into the engine though a air filter of some type weather it's stand alone or the main air cleaner, other wise you are introducing dirty air to the crankcase. I suppose the A/F ratio is off some, but it would be on the lean side which should help on exhaust smell, I doubt you will notice anything in how it runs. Next time I have my truck running, I will plug off the valve and see what the A/F does, my gauge will pickup even the slightest changes.
