Post by
rn240sx »
https://forums.nicoclub.com/rn240sx-u12444.html
Sun Aug 24, 2014 9:11 am
OK… yes this thread has been DEAD for over a yea but i am bringing it back because i am about to re-do my pcv & vc situation…
Currently on my ka-t i have my PCV disconnected from my intake manifold… The intake manifold ports has been sealed shut. The pcv is just sitting in that oil / air separator box attached to the block in CLOSED mode because there is NO vacuum to pull it open. So now at idle, cruise & boost, all the crankcase gas or whatever you want to call it is escaping thru the valve cover breather.. I have a 5/8 hose attached to the VC and running to a glass bottle as my ghetto catch can.. Clear oil does come out but once it sits in that bottle it turns into a milkshake guessing from the E85 fuel that its mixing with… But the oil in my OIL pan is clean as can be…
The stock ka system is designed to have fresh air enter thru the VC and exit thru the PCV… When i was NA, and when the PCV was connected properly, i could place my finger by the VC and feel it sucking in air… because the intake manifold was sucking out the crankcase gas via PCV… So it only made sense that since the PCV was the exit door, the VC was the intake side… For a while i left that VC VTA and NEVER had any oil come out… But eventually hooked it back to the intake…
Then went turbo… Left the stock PCV setup functional… Worked good while at idle and cruise until i went into boost… At that time thats when i started to get oil shooting out the VC … WHY..?? My guess is that the Boost closed off the PCV leaving the crankcase gas only one exit.. which happened to be the VC… Thats when i put my ghetto glass bottle on the VC to catch the oil…
Later i removed the PCV due to boost leaks on 2 of those hoses off the intake manifold.. I just removed the 4 hoses, cut the nipples and sealed them off… Then removed the hose from the PCV and just left the PCV in the oil air box attached to the block (again, permanently putting the PCV in closed mode)… So now i am ka-t with a shut PCV valve and all my crankcase gas' are exiting the VC all the time..!!
So again, according to the FSM, fresh air enters the VC & bad contaminated gas' exit the PCV… Im assuming the fresh air is there to help keep the contamination down to a minimum while the PCV helps to remove the bad gas… OR the fresh air into the VC is to help aid in allowing the crankcase to have a good ventilation system..
I have read about 1 catch can setup, PCV to catch can to intake manifold. Works great while at idle and cruise, but under boost the PCV or check valve will close, then the crankcase has to find another exit which is the VC which is usually hooked up to the turbo inlet.. which guess what it will start to get… Nasty oil vapors… which will be passed into the piping and intercooler… etc u get the idea..
the next setup is putting in 2 oil catch cans…. One for the PCV and one for the VC (while under boost). The one for the PCV seems to work fine while at idle & cruise.. But once in boost, the PCV or check valve will close to effectively forcing that crankcase gas to find another exit, which is usually out the VC… which in tern pushes into that 2nd catch can and back to turbo inlet. The only downfall i see is that when off boost, the VC is supposed to acting as a intake for fresh air… What fresh air can it get if its connected to a catch can which is full of nasty oil vapors… ?? The inlet of that catch can is where all the nasty oil and crap GO TO… Once the VC reverts back to intake of fresh air.. its not going to get any fresh air..
Then there is the PCV & VC vented to atmosphere… Which is kinda how my setup is. This setup we vent the PCV and VC to a catch can with a breather filter… If you put the PCV to atmosphere, it will NOT open because there is NO vacuum to open it. So running a hose from it to a catch can is worthless IMO. So if the PCV is now permanently closed, there is ONLY one exit for the crankcase and that is the VC which you have sent to a catch can with a breather filter…
This setup there is NO fresh air going into the VC to do its "factory purpose".. But you do have an exit for the crankcase to breathe out, how much it can breathe depends on what size your VC vent hole is and the size of the hose and the size of your filter breather.. They say this method contaminates your oil faster which requires more / sooner oil changes….
The next setup i saw was Tee'ing the PCV & VC together to the inlet of the catch can and the outlet to the turbo intake so that the turbo will evacuate the crankcase gas during idle, cruise and boost which seems like the perfect solution. BUT people say the turbo does not pull enough vacuum to extract the crankcase gas… Well, that is true.. there is NO Vacuum before the turbo, if any there will be like 1 inch… Here is the kicker that i see, people are leaving the stock PCV in there which again requires VACUUM to open… If the turbo cannot produce vacuum, then the PCV will NOT open which means the crankcase gas will have to find another exit… Which again is the VC. So again, hooking up a hose from a permanently closed PCV to a catch can is worthless. But with the VC also hooked to the same side, there is a exit for the crankcase gas to exit & be pulling in by the turbo.. Bad part is again, NO fresh air into the VC… This setup will work fine for idle, cruise and boost but* the No fresh air into the VC is a problem per the FSM and original engine design…
And here is what i plan on doing and its the best solution that i can "think" of while retaining ~full PCV function during idle, cruise and boost so that i can preserve my oil so that i don't have to do as much oil changes and to preserve internal seals and gaskets and so that the crankcase does not get "accidentally" pressurized under boost which will cause other problems….
Remove the PCV and place a 3/8 NPT to 5/8 hose barb into the stock air oil separator on the block… Then a hose from it to a GOOD catch can, then to the turbo inlet. On the VC i will put in a 5/8 breather because the nipple on the VC is a 5/8 which allows a good amount of air flow :-)
With this setup the turbo will be doing all the work. As it spins during idle, cruise and boost, it will be sucking out the crankcase gas' while allowing the VC to allow fresh air IN….. All this is done via a 5/8 hole on top & bottom which SHOULD allow plenty of air flow for that crankcase to BREATHE… Remember no PCV that needs to be pulled open by vacuum that does not exist via turbo intake…
The ONLY downfalls i see here is the physical amount of air flow the catch can will allow to pass thru OR the amount of air the turbo can suck out of the crankcase or if the catch can will restrict the turbo's suction.. Remember as the turbo spins and sucks out the crankcase gas, the VC is allowing air IN. Its a constant cycle during idle, cruise and boost… and remember again that crankcase pressure and blow by is at its peak while the motor is under boost so thats when crankcase evac is the most important..
SO… what do you guys think on my setup.. Im pretty sure my idea will work pretty good, but i think its a lot better than i some of the setups i can seen on the web… I am NO MECHANIC is any way shape or form, i am NO expert in PCV setups, i am not saying i know everything, because if i did, you would not be reading this.. LOL I'm writing this post in hopes to get your feedback and let me know if i am wrong… I am OPEN to all comments and corrections..
thanks guys...