Quote:
Originally Posted by Kingtal0n
First of all, the carbon buildup on the valves issue has been shown to have nothing to do with the pcv system or oil aspiration via intake manifold.
Second of all, there is only a very narrow year range for DI performance engines that matter, which have the critical 'flaw' of not incorporating port injection. iirc its from say 08 to 2012. After roughly 2012 ALL performance engines use port injection on top of their DI injection to solve the valve washing issue so it never happens again.
Finally, there is no way a healthy engine can supply oil to the intake manifold through a proper baffle system. If you find oil there, then the engine was built or designed wrong, or the pcv is setup wrong, with no vacuum. Everytime the engine is in boost, And also during cruise, ALL the time: there must be a healthy vacuum in the crankcase of 1 to 3" Hg or the pressure will cause oil to invade seals. Actually oil will still gradually pass oil seals as the seals age and oil works it's way into everything, especially synthetic because of it's size and uniformity. So having a vacuum pcv crankcase is what allows engines to achieve 200,000 miles and 15 to 25 years of service with very little oil bypassing until finally old age.
If a brand new engine is run without this pcv vacuum that will severely cripple the mileage and age-ability of all the engine's oil seals. You will find oil leaving every orifice and pushing into every seal, one by one they will leak especially during times of stress "events" for example where the engine is run hard repeatedly without a reasonable crankcase vacuum, eliciting the response of adding a catch-device when in reality what really needs to be done is a vacuum needs to be applied to the crankcase somehow to keep the oil inside it and also protect the oil seals.
Thus: The catch can "answer" implemented with an atmospheric vented setup knee jerk response is actually facilitating the destruction and degradation of all the engine's oil seals, and helping to push oil into all orifices and channels as it searches for an exit. If you've ever seen what a broken piston does to the flow of oil leaving the valve cover baffle during boost and spraying all over the car you will understand that the pressure inside the crankcase is absolutely necessary to monitor and control in order to prevent oil from leaving an engine.
in other words, a crankcase pressure being over atmospheric will also contribute to pushing oil from the crankcase, and all vented setups will experience some pressure
With the correct pressure drop inside the crankcase, and a healthy bottom end no engine should push oil. Even the force of oil being slung away from the rotating parts should be accounted for somehow, with baffles, shields, windage trays, the factory usually provides decent versions but if it became an issue you are still responsible for modifying and fixing that issue. That is the purpose of those parts and they must be present for the application.
Protected by both pressure and physical force, no oil seals or oil orifices can flow/eject any oil content, nothing can blow out of the motor.
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(sarcasm)Oh is
that why every engines intake manifold is coated internally with oil film?(/sarcasm)
GTFO here dude. Oil vaporizes and becomes a mist that will absolutely flow through baffles and a pcv valve.
Also LOL at every DOHC head being full of oil. Maybe on an RB or the exhaust cams on a VG30DETT, but most engines have adequate head drains, and on an SR20 it's a giant front timing chain hole. No way that oil fills the head above the valve stems.
You assume that the people who design engines both really care about oil consumption, and never make mistakes. They care much more about meeting emissions, and the myriad of engines with inherent design flaws disproves the latter. Do you know why the latest API service specifications for oil only allows them to contain 800-900 PPM zinc? Because zinc poisons catalytic converters and it's *gasp* consumed by the engine. I mean fuck, EJ25's are known to consume tons of oil in their bone stock form, and if you've ever taken one apart, you can see the thick, black film in the intake manfold from the PCV system. Install a proper catch can system and it pretty much goes away. Shocking!
There's plenty of correct information in your posts, but it's also full of assumption. Not every engine has an adequate baffling system. Just because your favorite OHV engine doesn't have issues, doesn't mean no engine needs a catch can or air oil separator.
Again, I believe a properly integrated fresh air feed and PCV system is the superior way to do things. I also think that draining the catch cans to the crankcase is harmless and convenient.