[Muscle Car Lover]

Originally Posted by axis

The 1LE has a OEM catchcan but it's on the clean side, which really doesn't help much. There isn't one on the dirty side, hence the reason for a catchcan. Don't know what GM is considering a oil separator, if it says it has two.

Thanks! Just looking for information. Here is the item from the LS3 article:
http://www.camarohomepage.com/ls3/

"There are two sides to any PCV system, the "fresh side", where air goes into the crankcase and the "foul side," where dirty air comes out. On Gen 4 engines, both sides have oil separators. The foul side separator is the most important because that's where there is oil in the crankcase ventilation flow virtually all the time. Blow-by goes in the crankcase, through the foul-side separator then is consumed in the engine.

LS3 has a new design for that separator. It shares the same location as the LS1's, but internally, it's quite different. Once again, computational fluid dynamics played a part in development, but this time, with the addition of some proprietary GM software code called “Rain Drop Analysis”. CFD with RDA is able model the flow of air in which oil is suspended as it goes through separator. The data gained from that helped engineers develop baffles which would better separate the oil from the air. This unique oil/air separator design is so effective that it was patented. At the time rain drop analysis was paired with CFD for the initial Gen 4 development in 2002, it was a revolutionary computer modeling tool. Even today, few companies utilize it because of the immense computer power necessary to run it.

Ideally, you want to separate all the oil and return it to the crankcase and only have the engine ingest air and blow-by gases. In practice, you burn some oil, but it needs to be as little as possible. It there's too much oil in the PCV flow, oil consumption will rise. With the LS1, when there was a lot of air moving through the PVC system at high speed but the engine was only lightly loaded; the system wasn't efficient at separating the oil from the air, so those engines suffered higher oil consumption than engineers and some 4 Gen Camaro owners would have liked.

Not only does the LS3 have significant improvement in its foul-side, oil/air separator, it also has less blow-by air flow under those conditions. Less blow-by under high-rpm/light-load conditions and a more effective separator means less oil consumption.

At high-rpm and wide-open-throttle, blow-by flow can reach the capacity of the foul side. That capacity cannot be so large that it would never be exceeded because it's undesirable to constantly consume large quantities of crankcase air through the intake side of the engine. You want to consume only enough that you're constantly purging the crankcase vapors adequately. At light load, there is an assist from manifold vacuum which insures constant crankcase purging. That reduces sludge formation and burns hydrocarbon pollution.

At WOT, there is no vacuum to help pull the air from the crankcase and, also, there is more blow-by; so you exceed the flow capacity of the foul side, which is sized for most normal light load operation.

Often there is enough blow-by at WOT that the clean-side air flow reverses. If that happens, it might force oil into the intake. That's why Gen 4 has oil/air separation on both the clean and the foul sides."

Maybe under heavy pedal use the external catch can gets anything that passes the other two.