ok...

under vac, the intake to valve cover supplies fresh air while the PCV to IM hookup evacuates the crankcase pressures.

under b00st, obviously, the PCV is closed.

this means that the crankcase now vents through the next path of least resistance, which is the valve cover-to-intake tube AFTER the MAF

if you eliminate that connection, and put a vented can to the valve cover, and cap the intake tube connection, the engine will now see air that was previously going to the valve cover under vacuum. it's metered air, and, previously, a bit of this metered air was feeding the crankcase. now it's not, and 100% of the metered air is going to the turbo now.

what i'm trying to prevent is any bullshit crankcase vapors getting into the intake tube under boost (since the PCV is closed).

a sealed can inline up there is NOT an option because that still includes vapors when the engine sees boost, going into the intake.

how does the ecu typically deal with that metered air going 100% into the engine now, instead of being bled off for the crankcase?

i'm sorry if this is confusing, but hopefully someone understands...

thx

'hatch

 

I think you are slightly confused.......

The hose coming from your valvecover to the intake manifold is vaccum assisted, meaning that the vacuum in the intake manifold helps PULL the vapors from the upper part of the motor. Which if you look at the block with the head off you have channels built into the block that let the vapors from the crankcase, naturally rise up through the block and either expell via the PCV valve or the valvecover, or both.

Under boosted without a one way check valve boost will pressurize the valvecover and continue to keep vapors from making its way up through the block, thus trapping gasses inside the motor.

All you need to do is vent your PCV and valvecover to a VENTED catch can and you will be fine, you MAF has nothing to do with it, I put these setups on eclipses and talons all the time

 

hose from valve cover to intake manifold? there is no such thing.

boost won't "pressurize the valvecover" (your phrase) if the valve cover is connected to the pre-turbo intake tube. that is impossible.

i guess i should have explained i know 100% how PCV systems work. i think that you might have assumed some things from my last post without completely understanding what i wrote....

i appreciate the help though.

so, assuming i know 100% how a PCV system works, which i do.

take what i asked specifically and see if you or anyone can explain what is happening.

under boost, the PCV closes...the PCV runs from the intake manifold to the block, lol. ok, so the PCV is closed. that means that there is no place for the crankcase pressure to go EXCEPT through the top of the engine now, the valve cover-to-intake tube hose. this spot on the intake tube is after the MAF, but before the turbo.

we know that when the engine is under vacuum, the PCV is opened in various degrees and crankcase vapors are going from the block, through the PCV, into the intake manifold.

when this is occuring, the valve cover-to-intake tube is pulling fresh air from the intake tube. it's a cycle.

ok.

that SAME spot that was previously supplying the crankcase with fresh air.

when the engine is under boost, that line is now the only exit for crankcase pressure because remember the PCV to IM connection is now a no-go, as the PCV is seeing boost and sealing off the block. so now the former air supply line at the valve cover from the intake tube becomes an exit line for crankcase stuff. the valve cover is baffled for a few reasons, and one of them is to prevent actual oil from going into the intake tube during this condition, but of course that doesn't work well. that is why these setups typically end up with oil in the intake tract BEFORE the turbo.

so, the solution for the valve cover issue is...

to run a line from the valve cover to a vented can. this way, under boost, the sole exit available ends up putting junk into the vented can and not the intake tube. also, when the engine is under vacuum and the lower PCV to IM system is working, the vent on the can allows the valve cover to have an air supply like it formerly did, albeit not from the intake tube any longer.

now HERE is my problem, lol.....

the line that you connected to the vented can....

that line WAS going to a spot on the intake tube after the MAF. like, right after it.

if i leave that spot open, obviously metered air that passed the MAF will be going out of that hole to the underhood area.

ok, so i cap it.

well, capping it causes the ECU to wonder why the bit of metered air that was supplying the valve cover with fresh METERED air under vacuum as described above is now not supplying the valve cover with air but in fact going into the turbo now, to be compressed enroute to the combustion process.

i know this because the fuel trims change automatically when this area is capped. that is because the ECU is seeing more air enter the turbo system now, esp under vacuum conditions when it previously was supplying the crankcase.

what is going on there? i think this might be over the heads of alot of people. i'm going to consult some of the more respected technical people out there like Jeff Evans and Mase, but i'd like to know exactly how this could be accomplished on modern MAF cars without issues because i know the change is showing issues on what i'm working with.

 

I think mr sponge is talking about the PCV on the valve cover (the small fitting), and there is also a valve cover breather on the valve cover?

The simple way would be to tune the car with your PCV setup the way you are talking about, with the metered air not going into the engine.

The best way, would be to take that MAF and drive over it with your uncles 4x4 and get something that isn't such a pain. Speed density, with AEM, Motec etc.. God i hate MAF's.

 

yeah, the valve cover breather.

re: MAP

haha.......

dude, i agree!

i loved MAP for quite a while, but now both of my cars are MAF. the si and the car in question, which actually isn't a honda, but a mazdaspeed3.

i know that might send up a red flag, as i'm a mod on a honda technical forum and i'm asking in one its subforums about a mazda, but the reason i'm posting in here is because i want to know what guys running boosted k20's are doing in terms of the secondary vented catch can connection. they are MAF, the ECU is modern, so there has to be some info for me.

NOT THE PCV to IM connection, but the valve cover to intake tube connection. how is anyone with a boosted k-series, or any other bewsted MAF honda running such a setup without having issues with the ECU and that 'mystery' new found metered air valve cover supply?

this mazda ecu is not cracked yet, really, and i can't tune around such changes. but i certainly know the benefit of not having crankcase **** going into the engine, so are the new school MAF honda guys running the setup i'm describing successfully?

 

I am not totally familiar with the Mazda stuff although I do do alot with BMW, Mercedes, and Porsche and they all fall victim to the MAF systems. Metered air systems are extremely temperamental, but you already probably realize this and subsequently realize why people switch to speed density so quickly.

Interms of your situation, I really don't have any good advice other than to deal with the crankcase "gas" situation by trying to limit the amount of oil that will inevitably make its way in to your intake tract as this is most of the problem with PCV "recycling".

If you can make any style of oil catch system in this pipe that allows the ECU to grab its air needed (idle, and PT situations) to keep your fuel trims in check (fuel trims are such a pain in MAF cars), but also does its job of preventing oil to enter your intake, and let PCV in so your seals and gaskets do not explode out of they're respective places.

Sorry if thats not much but until you have either control of your MAF based ecu, or you can convert to speed density thats all I can imagine as a solution to your issue.

Good Luck!

sander

 

Why not do a line to a vented can, and then a line from the same can to the pre turbo intake turbo to the spot you are refering to, it will still draw in air but cleaner air then what you are getting, the filter size and diameter of the bung that the filter is placed on will determine how much air can be pulled. I use to use this type on my car a while back when i had room to run a tube on my turbo inlet, the vented can kept it from sealing 100% positive valvecover and PCV gasses but the vacuum created in the can by the turbo helped pull them out of the motor.

Is the mazda really affected that badly by capping it off? thats crazy because we do this on DSMs all the time and just cap the port off on the intake tube after the MAF.

 

It will be fine, you can do it either way you will probably get a better result if you run the tube from the valve cover to the intake pipe. {I don't on my nissan but am having trouble on high boost.} If running higher boost it will prevent your dipstick from blowing out under extreme conditions. If you really don't want any oil to enter the inlet tract and still wish to have good crank case ventilation then you could look in a Exhaust evac ventilation system, bit of work involved and skillfull welding needed. Checkout freshalloy.com for info I would post a link but am banned for some gay reason.

 

that is a thought. the only problem i have with that though is that the intake tube will be exposed to atmosphere through that vented can, you know what i mean? now, that might actually be the ticket and work, because this system is so weird, but i'm not really sure on how the ECU will react to having post MAF air going out of a hole to a vent under the hood. i see the ECU freaking out even more than it does with a capped intake tube spot. who knows, you know what i mean?

man i WISH WISH i had it as simple as the older DSM stuff. you guys are blessed, hehe. this new **** is so annoying! it's 2009 and do you know we still don't have a full cracked ECU, meaning, some sort of live tuning interface to 'flash' the ecu in real time? it's crazy, the platform in a few months will be 3 years old.....

sponge, sander, rex, thanks for the responses guys. i feel that the route i'm going to be stuck with is what sander said, which is basically just doing what i can with sealed cans or whatever is possible to keep the system 'sealed' to keep the ECU happy.

 

How badly does it run when the VC is just vented to a catch can?

 

Probably not a matter of running badly, but the ECU will throw a check engine light if the fuel trims get out of hand, really not hard to do on newer cars.

 

the best you can do is make sure you have well baffled catch can and use big enough hoses so that the velocity of the air moving through them is low enough that it dosnt suck air, you can make an intake tube with equally as big fittings/hoses.

instead of the filters on top of the can, run it to the intake tube, but again, use BIG hoses, that will allow the system to move a big enough volume of air but keep the suction down.