Sorry, that's above my pay grade.
This is from the workshop manual:
So under normal operation the air is sucked in and only in some boosted or high load situations oily air is pushed out again. Makes sense for boosted applications: After boost the air compression decreases and the equalization of pressure will cause crankcase gas to move out again. Similar effect that would appear in high load applications for an NA engine during racing situations I suppose, like @NeedForGreen said.
Not necessarily. There's other possible 'explanations:'
I doubt the normal blow by will damage anything in the average lifetime of the car. I got mine purely out of curiosity and while I'll keep in installed, I wont feel the need to get one on any other vehicle I own. I checked and emptied mine after 1k miles and now just added it to the oil change routine every 5k miles.
I've removed a lot of intake plenums on older cars to get access to injectors, valve cover gaskets, etc. and every one of them had liquid oil in different places of the intake. All of them would have oil drip as you turned the manifold in any direction other than the normal position as it sits on the engine. You can clearly see a coating of oil inside the runners, etc. so that prompted me to put a JLT oil separator on my car when it only had 200 miles on it. I've emptied it twice since I have about 2,000 miles on it and each time there was maybe an ounce or so of oil in it. The second emptying seemed to have a little less than the first time, which is expected as the engine wears in over time (I also noticed lower ET in 0-60 times as it breaks in). It gives me a good feeling knowing the oil I'm dumping out is not getting into the intake.
CJPony site just says it will make a big mess.
They should!
For DI systems, the fuel spray never touches the intake valves. Without a catch can, oil vapors collect on the valves and valve openings. Walnut blasting works to remove these deposits on high mileage cars. My opinion: all of the chemical solutions are pretty much snake oil. If you have direct injection, get a catch can. Port injection cars don't need one. That's one of the great reasons that Gen 3 coyotes have the benefits of both.
I agree that it's snake oil but the seafoam smoke out is fun...
Oh great, I was telling myself that with port injection, I really don't need it, but now you tell me that you drain couple of ounces per change, and I here a voice in my head saying, "you know you want to catch that..."
Yes it does in fact catch some blow by. I don't think anything harmful it may do would impact the life of the car though. I don't feel anything in the butt dyno either so the robbing power thing seems like more myth to me, unless the power it robs equates to duck power witch we all know is about a 63.72dp to 1hp ratio. Next thing to try is a throttle body spacer to get alll those mpgs haha!