crankcase ventilation - questions

[terrytcl]

i'm working on rerouting my PCV lines, since i have most of the car apart.

can someone confirm / answer these questions?

1) valve covers vents are joined together and then are connected to a port on intake manifold. correct?
this connection is hidden under the intake manifold, but if it connects to the intake manifold, where specifically? and does this line have a check valve to prevent boost pressure from going to the valve covers?

2) the main pcv looks like it comes from the oil/water separator on the short block, which it seems basically separates the water from the oil before it hits the oil pan. am i correct in saying that there are 2 lines coming from the oil/water separator and only the driver side has the check valve (PCV valve)? if so, this doesn't make sense as the passenger side has no check valve protecting it... and also, path of least resistance means all of the oil/water vapor will go through the passenger route and then ultimately to the turbo inlet on the passenger side. OR? is there a check valve somewhere under the intake manifold too?

my real question here is that if the passenger side and driver side lines coming from the oil/water separator are split, wouldn't it make sense to diconnect the driver from the passenger side and have each line going to the turbo inlet on its own with an oil catch can? of course, in this case, each line would require its own PCV valve.

3) someone explain to me why we have pressure limiting valves on the pcv lines.


ultimately, here's my opinion. i'm looking for someone to refute my assumptions.

1 - disconnect the driver's to passenger side joining hose from the pcv valve, remove pressure limiting valve, and connect an oil catch can inline from the exit of the pcv valve to the driver side turbo inlet.

2 - connect a pcv valve on the open passenger side, remove pressure limiiting valve, and connect an oil catch can inline from the exit of the new pcv valve added to the passenger side turbo inlet.

3 - connect an oil catch can inline between the hoses from the valve covers to the pipe leading from the intake manifold (that's if there is a check valve). if no check valve, add one inline so that no boost pressure goes to the head.

thoughts?

[hahnmgh63]

Terry, I will answer a little of this as I know it, coming from the cylinder heads & block are both vented through the pressure limiting valves and the to intake just upstream of the Turbo compressor (see pg. 16 of the RS6 study guide). This is why I mounted two separate oil catch cans, one on each side between the pressure limiting valve and the Turbo intlet. As I mentioned in the Fluid Motion post, on a Turbo car these should be sealed catch cans, 1 inlet, 1 outlet, and not vented. For some reason Fluid motion did not know this in the beginning and surprised me that a tuning shop of Turbocharged cars didn't know that? If you need a copy of the RS6 study guide let me know, it was a Sticky at one time but I'm not sure if it is still there.
To further answer your question about the two pressure limiting valves, first of all, the crankcase pressure varies as we all know due to boost, engine RPM, etc... The intake tract is unpressurized upstream from the Turbo's which means the MAF's are metering unpressurized air (hence, the MAF seals should be relatively easy to keep sealed). The intake track may have some vacuum (slight) from the air being sucked into the Turbos, this is where the crankcase ventilation air is dumped. The Audi explanation of the Pressure Limiting Valves is: The pressure limiting valve limits the vacuum in the crankcase. If the vacuum in the crankcase exceeds a defined value, the diaphragm is drawn over the connection against the force of the spring and closes the
connection. The valve is designed in such a way that it allows a small quantity to pass through when closed. This prevents the engine oil being drawn into the intake tract and has no adverse effects on engine breathing. Hope this helps.

[skribe]

A DIY catch can(s) install how-to would be a true thing of beauty.
Left my own devices I would hook it up to the blinker fluid reservoir :)

[terrytcl]

i've studied that page of the study guide... and the way they have it drawn, it's a little confusing what connects to the intake manifold and what connects to the water/oil separator in the short block.

i can understand that the water/oil separator is connected to the pressure limiting valves (although, i'm not sure if mine are working or not... disconnect one and try blowing through each of the ports of the valve... i don't see or feel a difference. very slight if that)... maybe if i drew something up, it'll make more sense, or edit the page of the study guide.

[terrytcl]

http://i26.photobucket.com/albums/c104/terrytcl/Audi%20Trim/1.jpg

[terrytcl]

hopefully, you guys can see photobucket pictures... i posted a picture of what is the correct connection.

so, here are my questions -

the orange line - which is the ventillation for the valve covers, but is connected to the oil/water separator... how efficient is this? i'm assuming that the vacuum drawn by the blue through the red line is also pulling a vacuum for the orange line (valve cover ventillation). so... oil/water junk coming out of the cylinder heads get dumped into the oil/water separator. it'd make more sense to just plumb it to a high vacuum source like one of the inlets of the turbos with a good oil catch can inline.

also... it seems that the red line is the main ventillation line from the oil/water separator in the short block.... and with that... the blue line is basically, the main vacuum source with the passenger side turbo inlet also aiding in the vacuum. so, PCV valve is acting like a check valve to prevent boost pressure from entering the PCV system.

ultimately, you'll have oil/water vapor going into the passenger and driver side turbo inlets as well as the intake manifold (at blue line connection). that's a lot of oil vapor going into your cylinders.

[terrytcl]

what if -

http://i26.photobucket.com/albums/c104/terrytcl/Audi%20Trim/2.jpg

[terrytcl]

follow only the orange and red lines in the modified system above.

to maximize vacuum... i'd tie it all together and... to maximize oil from the air, add an high efficiency oil catch can where red and orange lines meet.

[terrytcl]

anyone? comments?

[JSRS6]

How much of an improvement are you looking for over the current system? Would the reduction to one pressure limiting valve increase the use, and decrease it's life span? Where would the catchcan be mounted?

[TozoM8]

I've learned a bit about the crank case vent system when TT-ed my S8. First I needed a check valve to keep boost out of the cc. Then I had to deal with the engine created cc pressure. I went with the catch can first, but it it requires daily checking. In humid days it would fill up faster. Next morning it was frozen shot so the cc pressure blew the valve cover gaskets. Now I have a tee on the hose from the cc to the PCV and a hose running to the air filter with a small filter on it. 1k miles a the little filter is still clean.

[terrytcl]

i think the big thing that i'm trying to get rid of is the fact that the ventillation of the valve covers combines with the ventillation of the air/water separator.

with the addition of a catch can, you wouldn't be dumping the crap into the air/water separtor only to be sucked up again to go to the turbo inlet pipes.

there's plenty of room for a catch can on the passenger side. http://www.saikoumichi.com/ catch cans is what i've been looking at. if i go with their largest one, i think it'll be able to handle the rerouted PCV lines as i have a couple treads above.

[terrytcl]

sorry about the crude paint drawings, but that's all i have available.

so... here's what the stock system is doing -

http://i26.photobucket.com/albums/c104/terrytcl/Audi%20Trim/3.jpg

[terrytcl]

and this is what i'm proposing.

http://i26.photobucket.com/albums/c104/terrytcl/Audi%20Trim/4.jpg


the main reason for this is because i had to clean out a bunch of clogged gunk build up in the valve cover ventillation lines. it just seems that there's not enough vacuum.

[terrytcl]

reason for the check valve is to prevent any excessive crankcase pressure from leaking into the valve covers.

[JSRS6]

I saw the same thing when removing the Ventilation lines off the S4 I sold to my friend. We are replacing a bunch of top end gaskets, and cleaning everything up. The inside of the hoses looked like an artery in desperate need of a bypass surgery.

[JSRS6]

And doing the tb service of course ;-)

[terrytcl]

I saw the same thing when removing the Ventilation lines off the S4 I sold to my friend. We are replacing a bunch of top end gaskets, and cleaning everything up. The inside of the hoses looked like an artery in desperate need of a bypass surgery.

exactly, and i think that if most of you started taking off your valve cover ventilation lines... you'd see the same too. it is definitely a build up (like cholestrol).

[speedtrapped]

Terry or anyone, any photos of your set up? I am really starting to consider using my CC that has been on my shelf for 8 months, especially now running hi boost.

[RS8]

So what is the best oil catch can for RS6? (and I think we need 2 = one on each side of the engine)

Mishimoto?
http://www.mishimoto.com/compact-baffled-oil-catch-can-2-port.html

JTL?
http://jlttruecoldair.com/ZenCart/index.php?main_page=index&cPath=378&zenid=e9ca3e856a27b874b45dc393c771d028

Saikou?
http://www.saikoumichi.com/internal_baffle_design.html

Or another one?

[hahnmgh63]

Looking at the three you posted I don't like the Mishimoto as it doesn't have the mesh filter which I do believe helps a lot with the separation of the oil. I'm using two that have the mesh and are more costly but I think these other two are just as good as the ones I'm using. Just make sure they can supply the proper inlet/exit sizes you need and you should be good to go. I have heard good things about the Saikou Michi separators and may go with them for my Cayenne Turbo. Just FYI, I'm using these but would probably have used the Saikou Michi if I had known about them first. http://www.eliteengineeringusa.com/choose-your-catch-can/

[RS8]

But Mishimoto have 50 micron bronze filter instead, don't you think that will work as good as mesh filter?

What is really good with Saikou Michi is that they can build it as you like, but one big problem is that you can't take it apart to clean it.

What's great about JTL is that the inlet and outlet are on opposite sides.

[RS8]

I think I will buy two from JTL


Do you have any opinion about JTL or you think someone else is better?

[hahnmgh63]

No preference myself. Just need to make sure it has the proper sized fitting for inlet/outlet so you don't have to adapt down then adapt back up again. Many of the inlet sizes are small.

[RS8]

Mishimoto have two 1/2" hose fittings.

JTL have no fittings but it has two 3/8"NPT threaded holes.

On Saikou you can choose between 3/8" - 1/2" - 5/8" ID or on the bigger also 3/4 or 1"
So maybe Saikou is the best.

I think I need between 5/8 and 3/4
(correct size outside nipple is 17mm=11/16")

[RS8]

JTL Will not be good because it has too little hole only 3/8, it must be 3/4 or bigger.
Mishimoto have 1/2 which is bigger than JTL but not enough.


Saikou can build it as I want BUT it is over 10 weeks delivery time?

Do you have tips on any other model with big connections, and that you can buy right now?

[RS8]

Any pics? on how people have modified the crankcase ventilation on RS6 ?


I just realised it is only 1 thin connection on the engine that all gases comes from = one of the two on the crankcase.
valve covers is only connected to the connection number 2 on crank case.

[kismetcapitan]

forgive my ignorance; I really don't understand any of the systems on my car :( but isn't it possible to run a much more simplified system (outside of emission-controlled states)? as in, run the crankcase breathers to an oil catch can, then vent the thing to atmosphere? There's a whole lot of hose and whatnot that could be tossed out - those pressure limiting valves for instance? I've done this in the past on other cars out of fear of the effects of oil in the intake - I understand the whole point of the system is to burn off the oil emitted by the crankcase breather system, which is better for the environment. but oil also causes the intake charge to have a dramatically lower effective octane as well.

It's apparently pretty bad for the atmosphere though - it doubles the pollution of a non-catalytic exhaust....