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Truth but AL is quite tricky. But no better time to learn than the present
You talking pre turbo intake or IM?
Intake pipe. or anywhere for that matter. One of the first things i did with my car was put an externally vented catch tank on the car and remove the pcv valve. bunged the intake pipe off and eventually fabbed a new one. and bunged off the intake manifold
The primary concern is 2 fold - Description:
The V2 STM Sealed Engine Oil Catch Can for the 2003-2006 Evo 8/9 is designed to help keep vacuum on the crankcase at all times. By doing this, it will reduce the amount of oil that passes by your turbo and engine seals. Even more importantly, It will help your piston rings seal which will create more power with less blow by.
Ever since FP started upgrading turbos the thing they keep beating into everyone is that it needs constant vac in order to keep the seals intact, otherwise it just acts like a blown turbo when its actually not.
So lots of schools of thought here as usual, but for you regulars it seems:
1. Dallas says to delete the intake pipe hose, and leave the intake manifold/PCV bit, and make the back fitting 10an as depicted as a single into a vented catch can.
2. Bee says to dump both VC fittings into a vented catch can and light that b*tch on fire
There is a reason why the official crankcase thread is a million pages long. Many different schools of thought and more than one way to set things up with success.
Personally I like routing it back to the pre intake pipe so I can leverage the turbo on boost for suction to pull CC pressures out of the VC. My setup is pretty close to stock actually but it's worked for me thus far. At one point I did blow out the dipstick so that's when I opened up the side port to -10AN.
So essentially my setup as mentioned is plumbed like the factory, except side port is drilled out for -10AN baffles removed cleaned then reinstalled all that good fun. I have 2 sealed catch cans. One sits inline from the side vc port then gets routed to the pre turbo intake. The other can is inline the back port between the VC and IM. I still use the PCV there and also have a separate check valve so I dont pressurize the catch can from the IM. During boost the side port is the only one doing the venting but has been enough after opening it up. The PCV closes in boost but with the location of the catch can I didnt want to pressurize it or the plumbing going to is so another check valve there does the trick.
Hope this makes sense hard to describe it without getting wordy.
is designed to help keep vacuum on the crankcase at all times.
needs constant vac
This is just a fallacy, you can not pull any true vacuum in the engine. You can only work to get to a neutral pressure, or down to roughly 1 ATM absolute, when in boost. And if you think you do have a vac, tap a gauge into your oil cap or some where in the cover (not into the line you're trying to pull a vacuum on).
There are ways to actually create a net vacuum, but its not from drawing through the intake pipe.
Personally I like routing it back to the pre intake pipe so I can leverage the turbo on boost for suction to pull CC pressures out of the VC. My setup is pretty close to stock actually but it's worked for me thus far. At one point I did blow out the dipstick so that's when I opened up the side port to -10AN.
I would also like to see a gauge reading on the intake pipe itself to see what kind of vacuum is created there. If you were seeing any obstruction of the filter/maf, that would be a strong reason to change as you really want no resistance to flow pre-turbo.
My guess is, the only strong reason to pump the crankcase venting to the intake is just to keep the nasty fumes from turning the engine bay into a gunky mess over many miles.
Pulling a vac on the CC won't lower blowby. Blowby is purely dependent on rings, PWC clearances and some small piston features.
I've had good success (no big issues or failures) pulling a vacuum with the intake as well as using slashcut venturis on the exhaust. As others have said, under boost you're never going to have a negative pressure in the CC, blowby is too much even on a tight engine. But rings seal better at high RPM so I see it as beneficial to have a vacuum source to pull blowby vapors out during idle and vacuum conditions when the rings do not seal as well.
The biggest reason I can think of for FP's mentality is because everyone uses those push in fittings on the side of the valve cover which don't actually do anything other than look pretty. If you drill the side port larger you'll pretty much never have CC pressure issues whether the line is VTA or a vacuum is applied. Making the rear line go to the pre turbo intake or VTA is an extra measure that would also work well, but it needs to go to a can because it doesn't have any baffling below it like the side vent does.
Getting rid of the PCV valve and blocking off the port on the intake manifold would be a good starting point. The CC issues we experience are under boost when the most CC pressure is created and under boost the PCV valve is closed so that rear line does nothing so long as it's going back to the intake manifold.
Dont get me wrong I'd bet inside the VC there is still new pressure not vacuum. I guess my point is the side port is pushing the CC pressure outward regardless. If you VTA then well, its venting but there is still pressure in there. Now say that's pushing outward, the force against it is our atmosphere. If you route it to the pre turbo intake if the intake does produce any vacuum, which is has to since its pulling in air to the turbo then now the net pressure is less by a magnitude of whatever vacuum the turbo is pulling.
Keep in mind there's other variables to how effective your vacuum source is. Putting the line at 90* to the pre turbo intake won't pull as strong of a vacuum as something put on at 30*. If you're familiar with the venturi effect it's all related to that.
IMO, as long as your catch can is properly filtering the vapors and the outlet is clean air, then there is no downside to using a vacuum source on the outlet of the can.
I believe I have fixed *my* crankcase pressure issue, with ebay parts. lol i know thats 2 BS statements but honestly I havent touched my test setup since because it just worked finally.
It involves the Y fitting needed in the rear port to the manifold + 1 more check valve, and 2 of these $18 oil separator/catch cans small enough to mounted high and drain back to the oil pan
<had to test the upload first>
It's looks cleaner than the diagram. I'm using 12mm silicon hoses btw, nothing too serious. anyway that "optional" inline oil separator is dry, i just added that to finally see whats happening on this side. my intake hose is dry finally, my downpipe has no black soot! I honestly could not believe it worked and I still have a few aluminum check valves left. I was planning to upgrade the 'reducer' and stock check valve since it needs a lots of pressure to open it up
I have not tested it in track day situations though. just autox and redlining 2rd & 3rd gears on the freeway
Last edited by ViciousLSD; Jun 27, 2019 at 10:00 AM.
One thing I still don't understand is why changing to rear port to a larger port would yeild more "air" and less "oil" in the catch can. A hole is a hole, if the intake pipe is indeed producing that much pulling effect then it won't change the result of a quart+ of oil leaving the engine. The other issue that remains is the oil condition. When my setup was rather simple and oem, rear port to oem check valve/IM, side port "hanging out", my DOM50 would still have a clear/red hue to it after a weekend. Now it's black and moisture ridden after a couple sessions.
One thing I still don't understand is why changing to rear port to a larger port would yeild more "air" and less "oil" in the catch can. A hole is a hole, if the intake pipe is indeed producing that much pulling effect then it won't change the result of a quart+ of oil leaving the engine. The other issue that remains is the oil condition. When my setup was rather simple and oem, rear port to oem check valve/IM, side port "hanging out", my DOM50 would still have a clear/red hue to it after a weekend. Now it's black and moisture ridden after a couple sessions.
It won't yield less oil, the point of enlarging it is so there isn't excess pressure in the CC. And you're right, a quart of oil leaving is still a quart leaving, but no CC setup will fix that, it's an engine issue.
What was the timeline between those two setups? Still the same engine build, same tune, same fuel? There's a lot of variables that can effect quality and quantity of blowby vapors.
Jun 26, 2019, 08:48 PM
