I've been posting here quite a bit about catch cans and if they are useful or not on the clean side. Anyhow, I will update with my results eventually but I had a few questions/comments. This is all regarding the GS/Z06 dry sump setup.

1) Dirty side catch can goes between valley cover and behind throttle plate. Will a one way valve on this help anything for an UNBOOSTED car? The flow should never reverse since the TB will always be under vacuum or at 0 pressure, where as the crank will always be at 0 pressure (gauge) or pressurized by blowby. I cant conceive of an instance where flow will go backwards from behind the TP to the valley.

2) Clean side catch can goes somewhere FORWARD of the throttle plate (always under 0 PSI when throttle plate is closed/nearly closed, POSSIBLE vac under WOT) to the oil reservoir. I can see this side flow reversing under certain conditions... should I have a one way valve here?

Now please correct me if i am wrong in my understanding: the "clean side" is actually feeding air from in front of the throttle plate (behind the MAF, so metered clean air) into the valve covers, through the heads into the engine, which is producing "dirty" air, which is pulled through the valley cover behind the throttle plate due to the vacuum in the intake manifold. At idle/partial throttle, with low load (minimal blowby) the clean side + dirty side is at equilibrium in terms of total air flow. Therefore, there are no issues with metering of air.

under load however, there is no vacuum behind the throttle plate (wide open) - possibly a little vacuum due to the venturi effect of air flow over the orifice but that is arguable and may be offset by blowby. At WOT, the flow from the clean side POSSIBLY reverses due to blowby and air goes from the valve covers into the FRONT of the throttle plate. We know this occurs since people have had their cars leaking oil from their air filters... possible reasons include too much oil, too much blow by, etc etc but it DOES occur under certain conditions.

Is this a good summary?

 

I almost forgot my real question. For the Elite Engineering "clean-air separator", which replaces the dry sump reservoir cap with a 2nd catch can, the instructions are to reroute the line forward of the throttle plate - instead of forward of TP to oil reservoir, it goes from forward of TP to oil cap drip* can. Then, they tell you to tee in the oil reservoir line to the valve covers. What does this accomplish? What is the difference between just capping the forward reservoir port? I tested vacuum/pressure from that port to the oil can and there is nearly zero flow restrictions and absolutely no check valves...

 

Yes, dirty side is off the valley cover, Clean side off the valve cover.
Note, both parts are internal baffled inside the motor.

When less than full throttle, you get your vacuum to draw the vapors out of the motor via behind the throttle body in the intake manifold.
At WOT, the vacuum in the intake manifold drops to zero, and there is a slight vacuum between the throttle body and the air filter, as well the piston blow by at full tilt boggy that is forcing pressure out of the motor as well.

To shot bus it, you want to keep the motor under a vacuum to dry the vapors off to keep the motor oil clean.

With a dry sump system, you use the single catch catch on the dirty side between the valley/ intake manifold port, and then use the new reserve tank with catch section in on the tank port to the port in front of the throttle body.



On a wet system, you can use a single catch can for both the clean and dirty side, but you have to install check valves you not drawing unmetered air into the intake manifold not flowing through the MAF sensor isntead.

 

Hi Dano, thanks for commenting in this thread! i have read roughly 50+ pages on these forums on catch can routing and your name along with MM comes up quite a bit. I have mine currently routed the way you have labeled - however, on EE's website for the C7 drysump setup, they now recommend not capping that front barb on the oil tank and instead routing it to the valve cover line via hose barb.

My confusion is: whats the difference? the valve cover lines attach directly TO the back barb on the oil sump tank....

 

The LT motor in the C7 is a different animal, with it shutting down cylinders to save fuel, hence locking the vavles closed, but the piston still moving up and down in the block.