LS3 Stock Oil Separators?

[Muscle Car Lover]

Reading through some technical articles on the LS3, it seems there are twin oil separators in the PVC system. Do they suck? I am guessing they do if everyone gets an additional catch can. Anyone know much about this?

[Muscle Car Lover]

Maybe I am missing something or my question was so dumb no one wants to embarrass me, which is very polite and nice!

Really though, just an honest question.

[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.

[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.

[Muscle Car Lover]

Ok, not much discussion on this. I guess I will pass on the can.

[DefiantXSoldier]

Search the forums for your answer. You will get people on both sides of the fence on this topic. There have been plenty of discussions over the catch can topic. Try looking in the 1LE forum


Sent from my iPad using Tapatalk

[Muscle Car Lover]

D, thanks. Trust me I am a scientist and I have read all the forums over the past 3 months. No where does anyone discuss the stock oil separators.

[Indydriver]

LOL, you sure are impatient.

No doubt GM recognized blow-by as a significant issue in earlier Gen Hi-Po V8s and devoted some resources toward new designs to lessen it. Note that your article says "less" not "eliminate". So the current Gen is better which you can take as having a lesser need for a catch can. If you've read all the threads on this, you've seen the significant amounts of oily goo everyone pours out of their CCs. That, plus the universal recommendation of every engine builder here is good enough for me. One of the best was documented by one of the cam installers with pics of the piston crowns covered with carbon crud by an engine with no CC. The whole thing is very logical. It costs $200. It's an easy DIY. Makes sense to me since I plan on keeping my car for the rest of my life.

[djnice]

Has there been any consideration given to whether the catch can could cause harm by restricting evacuation of blow by gasses?

[AITI]

Any internal separator will only be able to be at best, 20% or so effective or it will also catch and trap the damaging combustion by-products that contaminate the engine oil reducing it's ability to protect internal parts. There have been several revisions to the baffling systems in the LS based engines over the years, and this is the best to date...but it only marginally reduces ingestion and the issues associated with it.

No equal to a true effective external system.

At least they are paying attention.

[Indydriver]

Originally Posted by djnice

Has there been any consideration given to whether the catch can could cause harm by restricting evacuation of blow by gasses?

A catch can doesn't "restrict evacuation of blow by gases", it simply re-routs them into a condensation filter thereby keeping most of them out of your intake. Air has to flow through the crankcase to prevent pressure buildup at high rpm which, among other negative affects, would reduce horsepower. Allowing crankcase blow by to enter the combustion mix via the air intake contaminates the charge, reducing octane which reduces power and increases the likelihood of "knock" or pre-detonation.

Tracy Lewis at Rx builds drag motors and sees this phenomenon result in higher ETs, so his company has been very keen on reducing the introduction of crankcase blow by into the intake (while preserving helpful crankcase air circulation). The result is a very effective condensation filter called the catch can.

Anecdotally, I watched Bo White change out a throttle body at the Reveal and, as expected, the floor of the intake plenum was covered in oil. There is no where for this material to go but into the combustion chamber. I, for one, don't want it there.