Crankcase ventilation discussion and sort of survey

[fredio54]

you mean high boost and blocked off covers? ;-)

there are good ways and bad ways to achieve this, all the good ways create suction in the crank case. the bad ways are just open, the stupid seal their systems, or only vent them behind the throttle where on boost its closed and needs boost psi in the engine to vent anything...

most of those at a quick glance of the first page looked to be just open types. thats not ideal for oil life or power, but is fine for seals that would be pushed open by boost or blowby otherwise.

i always like it when you post in my threads :-)

dunno why. perhaps because you have a clue ;-)

fred.

[gavin]

Originally Posted by fredio54

most of those at a quick glance of the first page looked to be just open types. thats not ideal for oil life or power, but is fine for seals that would be pushed open by boost or blowby otherwise.

I know precious little about engines. I do pick up on things here and there though. What you mentioned was one of those things I recall hearing(the problem and a solution for it). It was offered as part of the "solution".

As for the Honda guys...well, ill admit I look over the fence and shake my head at times. but...there are so many of them and they have been doing this so long. You never know where a good idea will come from.

Gavin(semi-clueless)

[fredio54]

Ok, i was linked to this thread on miataturbo.net yesterday, and had a couple of longish chats with Rob and Brian (m2cupcar and neogenesis2004) about it. after that i had a think and stare at some pictures and came up with the following comment that i've pasted here for completeness :

Originally Posted by I

I couldnt find those pics that i thought i took. perhaps i never took them. either way, it doesnt matter as yours are of the utmost quality anyway :-)

Further to discussing this with both Rob and Brian last night, i was thinking about what i might do for one when i get back.

Currently i just have the longer labyrinth with the short oem hose hanging in mid air doing nothing much at all, and the oem pcv setup to my manifold much like stock.

For a number of reasons i believe its beneficial to have the pcv valve in place and functioning in some place or other. the pcv gasses can be greasy and oily with no negative impact on anything much, so the small labyrinth is probably best left supplying that in the long term.

its apparent from Robs fine pics that the longer labyrinth and its associated escape route are rather small and restrictive. most likely totally fine for normal NA use, but if you double the power it would be reasonable to double the blowby and therefore with nothing else changed double the velocity of gas through that port under load. given a tripling of power, probably a similar tripling of flow would be needed to keep pressures oem low.

in order to achieve tripple the flow at the same near 100kpa pressure you would need approximately tripple the area to pass it. thats not going to happen through that stock rear port.

my proposed solution is this :
oem pcv as it stands
rear port enlarged as much as reasonably possible
inside of rocker at the front of the head ported where that gas enters the labyrinth to slow the flow sufficiently to allow the oil to fall out
some porting of the baffles in the big labyrinth to ease velocity in there.
and lastly :

having had a think about it and a good look at Robs pics and my own, it would appear that the only decent place to put an extra port on the fe3 cam cover is at the rear of the intake cam. they were nice enough to put a cast in wall across in front of it to keep the oil away, and because its adjacent to the end of the cam no oil will be being flung there are high revs.

an exhaust scavenging system installed on this new port, or just another catch can and VTA (vent to atmo) setup.

given these mods you end up with the following situation :

throttle closed at idle/trailing throttle :
pcv draws dirty (wet) gas out of the crank case and clean air enters the original feed that goes to the turbo intake or vta. either the check valve on the exhaust scavenger is closed and no flow occurs or it too is scavenging some gas and disposing of it.

effect : clean air entering the case on one side, and dirty air exiting where it doesnt matter
result : engine oil stays cleaner and more effective longer because moisture is scavenged out at idle and on trailing throttle

throttle open wide scenario one :
pcv closed due to pressure in the manifold being 100kpa or greater
exhaust scavenging pulls so much gas out that clean air flows in through vta/vtt (vent to turbo) and crank case is kept clean under throttle too.

throttle open wide scenario two :
pcv closed due to pressure in the manifold being 100kpa or greater
exhaust scavenging pulls in exact gas that is being blown by and nothing flows through vta/vtt

throttle open wide scenario three :
pcv closed due to pressure in the manifold being 100kpa or greater
exhaust scavenging pulls in a bunch of gas, but not enough to prevent pressure buildup or more flow.
VTT/VTA dumps excess to atmo or turbo inlet

in this way you end up with low pressure at all times and clean air flowing in to replace wet blow by whenever opportune.

its possible that the exhaust scavenger would always be enough, this could be tested with the vta/vtt blocked and a sensitive pressure guage installed in the cabin and watched while thrashing the car hard.

after discussing this with them a faint memory of spots of oil that had exited my open pipe at speed came back to me. if they were exiting at speed then there was significant volume coming out. not surprising when you consider the more than doubling in power.

currently that seems to me to be optimum.

if the vent gas can be kept clean enough, then feeding it to the turbo is just fine. if it cant, a can with filter would be better so the intercooler stays dry.

fred.

[fredio54]

just had a read through that honda thread that gavin linked again.

it would probably be beneficial to fit a drain hole to the sump when doing your turbo oil return to allow catch cans somewhere to let the oil go back in.

i used to run mine to the dipstick hole, but thats no go for me now with the manifold where it is. i'd like an oil temperature guage anyway, and the sump is good place to do that, so i will probably end up drilling mine under pressure and welding it on the car anyway. i can do some extra drains at the same time.

some of the stuff in that thread is ridiculous though. four big hoses off the top cover and two big hoses off the block and a small drain to the sump and a pcv to the manifold. LOL. just run it without the cover man, it would be a lot easier :-)

[Nitrogen]

Coming in far too late to make any sense but here it goes :P

Are we talking about that exit from the valve cover that used to return to the intake on stock motors? I ripped that pipe off and put a little breather filter there only. Now as time has moved on and I've read a bit more:

1.) was this wise? the intake vacuum would have normalised pressure to an extent, now that it is just the filter, what is really happening in there.

2.) Did I completely misunderstand this thread hehe? If so I am sorry ;P

[fredio54]

so, in your fwd application, looking at the engine bay, you have a filter on the right hand side of the valve cover above the gearbox?

what do you have from the other port? short hose and pcv to the plenum?

if so, that is fine. at idle the engine sucks gas from the case and swallows it, and draws it in through your filter, under load, excess gas exits through your filter.

with much more power, the basic principle remains the same, just the "under load" part needs to flow a lot more than stock to avoid pressure and leakage and lost power.

fred.

[Nitrogen]

Ta Fred, Dude not sure what I am smoking, this is my setup, so equalization of pressure still occurs correctly.

I don't know why I had confused my setup as (1) having the breather and (2) having the piping.

[fredio54]

yep, thats sweet.

[fredio54]

M2CupCar did some good work yesterday!

He was having a few issues with leakage and boost, and upon discussion did a temporary setup for his pcv where he rerouted the in to the out and vice versa including moving the valve over. Apparently this helped quite a bit (not too surprising really. Heres the temp setup :



Further to that he pulled the fitting on the end out, and found the hole inside to be really small. so he replaced it with a large fitting. he also bored a hold in the back of the other bank.

Here are the results :

Small hole (quiet in the cheap seats) :



New hole in the other bank :



Ready to go (mint!) :



Cheers Rob!

Fred.

[M2cupcar]

Need to clean up the leftover silicon sealer from the OE chamber install and modify the exhaust chamber (I'm going to shorten it and flip up the leading edge with a drop off in the rear to dump oil), then reinstall it and the pcv chamber plate. Then I'll need to fab up a catch and find some big hoses. Those are 3/8" npt pipe nipples - that's the max size you'll get in those spaces. Step drill bit is mandatory for a good clean hole. Extra care is needed when overboring the OE exhaust side vent hole to keep from breaking through the top.

Seeing the size of the OE breather passage "L", explains why swapping that port with the OE pcv port showed improved vent under boost. Though the tube I used at the pcv port was small it was still 50% larger than the OE "L" tube.

[fredio54]

Originally Posted by M2cupcar

I'm going to shorten it and flip up the leading edge with a drop off in the rear to dump oil

another fine idea, take pics will ya :-)

[M2cupcar]

Ok - modded and install the intake side vent plate. It's using one cast chamber fin on the cam cover and one chamber fin that's tack welded on the plate itself, plus the fin(s) I added on the end. The stock drain hole is at the rear near the port exit as stock in the bottom of the well.

[M2cupcar]

I got the Kia cam cover installed as modded. Both lines run to my catch can with the vent filter on it. It appears to have resolved the cc pressure issues at high boost. I no longer see the weeping oil from around the cam cover gasket. I'm not getting much oil in the can either. But I can say that the can should be packed with something to help "grab" the oil vapor. My can is empty and after lots of hard boosting you can see some vapor escaping from the filter. And under the right conditions (top down, stopped at a traffic light) you can smell it. I think adding the substrate/packing to the can and running the filter back to the intake pre turbo would probably solve those issues.

[fredio54]

I've written an article on crank case ventilation here :

DIYEFI.org Forum - View topic - Crank Case Ventilation

Please be as critical as you can be, I'm interested to see the information and formatting etc be as good as possible. I hope it helps people in the future :-)

Fred.

[compnut21]

i have a question (probably cause im brain dead from work and missed the answer)

in this setup

why bother with the catch can at all? keep oil from dripping around the engine bay or emissions were my only guesses. also is there a better brand/type of pcv valve that can be used? maybe one that seals well under boost or something of the like? and last but not least... you talked about the venturi effect using flowing exhaust air to create vacuum... but why not incorporate something in the intake tract to create vacuum no matter what condition? i'm probably just not thinking clearly though, but please do criticize.