MD,
So you are running the Endyn sytem in an open configuration correct?
A properly designed closed system will maintain a slight vacuum under all conditions which is the case with my stock '99 GSR closed system. This system is actually better than a totally open system (one that has no conection to the intake manifold or intake tube and hence is not capable of pulling a vacuum in the crankcase) at keeping blowby vapors from contaminating the oil since it is always maintains POSITIVE (hence it's name) airflow through the crankcase. A totally open system is only a venting system and if properly designed, will just vent any blowby to the atmosphere and only keep the pressure in the crankcase from becoming above atmospheric. The oil will become contaminated more quickly with the open system because it isn't constantly flowing air; it only vents. This is the main purpose of a positive crankcase ventilation system, to increase engine life through reduced oil contamination. Older cars used to use what I would call a partially open system (one that had a PCV valve and connection to IM but had an open breather on the valve cover). These systems would maintain a positive flow at almost all times except at high load, low vacuum conditions when the IM connection could not maintain a high enough flow rate to keep up with the increased blowby. Under these conditions, the excess blowby would be vented directly to atmosphere through the open valve cover breather. Today it is not acceptable to vent directly to atmosphere, so the valve cover connection is hooked up to the intake tube or air filter so that no vapors ever escape directly to the atmosphere. This is a closed system. If the connection to the intake tube or air cleaner is placed properly then when the IM vacuum is low under high load and cannot keep up with the incresed blowby, the intake manifold connection will now actually have a slight vacuum due to the increased speed of the air flowing past it (venturi effect) so it will always maintain some positive flow, unlike the partially open system that would only be venting under these conditions. The really old cars had only a tube that went down under the car (road draft tube) that used the airflow past the car to help pull the vapors out.
