BluEVOIX

iTrader: (69)

I was curious if the stock pcv system has a check valve or not? I was searching and I couldnt find an answer to this. Either I got a whole bunch of pages of non related topics or a few pages regarding wet injection check valves.

So there are two ports on the valve cover, the breather one on the driver side and the pcv one by the passenger side facing the intake manifold. Correct me if I'm wrong or missing something.

I've searched and have seen people actually isolating the vacuum from the intake (called pcv delete?) Now people did mention that the valve cover leaks, so I'm guessing there is a check valve on the valve cover but it does not do a good job holding boost. Sort of like the pcv valve on my previous car Dodge SRT-4.

Well doesnt the valve cover need ventilation and vacuum to ensure better seals for the valves? Most of the muscle cars run pcv's but have it hooked to the exhaust pipe and use the venturi effect to create vacuum under the valve cover. And with this they see a gain in hp because of the idea that it helps better seal the valves.


Now since one end is the breather air goes in, and the other is the pcv where blow by gets sucked by the manifold. Placing a check valve right by the intake would ensure a boost leak free system while maintaining a vacuum under the valve cover during (non boosting) operations. And when you boost, the check valve stops the pressure at the intake and the breather end can release blow by gasses.

What do you guys think about vacuum being needed under the valve cover?

I havent had a chance to look at my car yet. I tried searching but there really isnt a well detailed picture or exact diagram of the pcv system (or at least from what I could search through quickly).

barneyb

The PCV valve is also a check valve. So, when the car is on boost, the PCV valve is closed and there needs to be somewhere for blowby to go. Hence, the second hose.

As for the valve cover leaking - yeah, given enough time the gaskets will shrink and the cover will ooze oil. I've never heard of this being a problem. You just need to replace the gaskets.

BluEVOIX

iTrader: (69)

Sorry I didnt explain it clearly, "valve cover leaking" I was referring to boost leak from the intake manifold to pcv connection. So there is a check valve on the pcv side... How well does it hold boost? I am asking because I will be using a catch can very soon and I need to know if I'll need to put my own check valve.

Also in regards to the "pcv delete" method of running the lines, by just leaving a catch can with a breather ("pcv delete" style), blow by gasses build up under the valve cover. Although excess gasses can exit and there is no pressure build, the remainder stays and contaminates the oil. Putting vacuum under the valve cover ensures that the blow by gas is sucked into the intake manifold for combustion and is replaced by fresh air.

I just thought I might mention that since many run the their pcv catch cans with the "delete" style after all the searching I was doing.

barneyb

Well, I've been around these forums a long time starting with the old "Talon Digest" in the early 90's. One thing I've never read is somebody having problems with the turbo pressurizing the crankcase because of the PCV valve leaking. Sometimes people have gotten the lines screwed up or plugged but that is a different story.

At one time it was said that if you road raced you could expect to pump a quart of oil an hour out the vent hose. While the latest versions of this engine appear to use an unchanged venting system for some reason it seems to work better now. The result is you don't hear too much about catch cans anymore. So, my advice is to spend you money on other mods and only go to an altered venting system if and when you need it.

BluEVOIX

iTrader: (69)

So blow by oil is not a problem with the EVO IX?

With the srt-4 a lot of oil vapors would travel with the blow by with the pcv connection. Those running no catch cans would have a good amount of oil come out from the intercooler when the pressure pipe was disconnected. That is why I wanted to run a catch can, to keep the intake side dry from oil.

Well as boost leaking into the valve cover, I didnt mean it as something that would cause problems under the cover. But rather another boost leak to worry about when doing a leak down test. Any pressure leak from the manifold to inside the valve cover would just result in it escaping through the breather side. But that could in some cases end up pushing oil out that side.

I'm new to the 4g63 platform and even to evo's and all wheel drive. I do how ever know a great deal about my previous car (Dodge srt-4) and a decent amount about cars in general. But I have a lot of searching and hands on things to do for the Evo to gain my knowledge on this new platform.

BluEVOIX

iTrader: (69)

Basically does the EVO pcv blowby contain a lot of oil vapors? My the catch can on my previous car would pretty much fill up every 2 weeks. (20 dollar diy catch can) I'm curious if a catch can is needed as badly as other turbo cars...

barneyb

You've got one thing right, it is oil vapor that comes over to the intake. I used to dip my finger into the oil that accumulated in the turbo intake of my '92 Plymouth Laser and that oil would be clean like just out of the bottle no matter what the oil looked like on the dipstick (this car had the 4G63). I put a gas filter on the vent hose on that car but never trapped anything. Also, I once pulled the intercooler just to see if it contained oil. It was dry.

But, to answer your question, my Evo 8 doesn't need any oil added between oil changes and I had until recently been putting on a lot of high speed highway miles. So, I'd say blowby oil is not a problem. Maybe the use of synthetic oil has something to do with this. Dunno.

Erik@MIL.SPEC

iTrader: (94)

I've got a Saikou Michi daul catch can, one for the PCV valve that gets rerouted into the intake manifold and the one that vents out the side of the valve cover back into the intake tract.

I just drained my catch can(s) and a significant amount of oil came out of the PCV valve one (I rarely boost since my car is untuned, so I am under vacuum most of the time). I didn't measure it, but I think it was close to 3 ounces, or maybe more, of oil. I was surprised it was that much. This is after about 2 months of use. Needless to say, I will be draining it more often from here on out.