Our PCV System and improving Vacuum on the Crankcase - Eliminate Smoking Turbo Issue

[mczimer]

Ok I know there are threads on Krankvents which are even more extensively debated but I'm trying to bring this concept more to the forefront of the discussion so that a larger percentage of our forum members can understand what's going on with our PCV valve and the smoking turbo issue.

I have attached an MS Paint diagram of how the flow is with our stock system. As you can see from the diagram that shows flow while NOT under boost pressure, the vacuum produced in our intake manifold, pulls vapors out of our crankcase through the PCV valve. Air rushes in through our valve cover vent to replace the air that's being sucked out of the crank case. As a result, there is somewhat of a vacuum on our crankcase but often not strong enough to allow draining of oil out of our turbo lines thus causing smoking.

In mockup #2 that shows the situation while under boost, our crankcase PCV valve is now shut since flow is only one way and that is OUT of the crankcase through the PCV valve. Our intake system, ahead of the turbo is mostly not under vacuum but under boost, when the turbo is sucking air in, a vacuum DOES exist within our intake system, whether that be a short ram intake, cool air intake or stock airbox. This vacuum is then pulling vapors out through our valve cover and back into our air intake system.

Summary, both under idle/vacuum conditions and under boost, there is always a source of vacuum on the crankcase BUT HERE IS THE PROPOSED ADDITION:

While the car is at idle, that's when we start to have smoking turbo because the vacuum flow to the crankcase ends up being too weak, most likely because air is so easily flowing BACK INTO THE CRANKCASE through the valve cover opening. If we install a check valve or just another plain old PCV valve here, allowing air to only LEAVE the valve cover, we can achieve the following:

1)Oil vapors are still vented into the intake because the added valve will allow
vapors to EXIT...

2)Since flow is only one way, and that's OUT of the valve cover, a much
stronger vacuum is maintained AT ALL TIMES within the crankcase.

3)Oil drainage out of the turbo at idle should be much more efficient in the
presence of higher vacuum.

4)Sealing of piston rings enhance in the presence of a steadier vacuum.

5)A LOT LESS WATER being pulled into our crankcase and then into our catch
cans. As a result of air NOT being pulled steadily in through our valve cover
port, there won't be the constant supply of moisture that precipitates out
into the crankcase/oil catch can. This should help reduce that hideous
sludge that we've found, caking up in our catch can and lines leading to the
catch can. Remember the peanut butter as some of us call it?

So my question is, does anyone see a problem with this? I think someone mentioned in one of the threads at one point, perhaps on the mazda6club, that it wasn't good to have too much vacuum in our crankcase but not sure if that's going to be a problem with our cars since it's kind of weak in the first place. I realize that this touches on the concept of the usage of KrankVents but in isolating out just the junction between our valve cover and the intake system, I think this may be a trouble spot where we lose a lot of our vacuum to the crankcase, at idle.

Thanks for staying with me on this long post. I think we may have something here that could improve our ill-designed PCV system.

[leon78]

@bnoon

[ljudgeii]

I tried that with a failing stock PCV valve back in 2009, worked fine til I went TBE with high flow cat

[silvapain]

Just move the line from the valve cover closer to the turbo inlet. That's Mazda's solution, and that's all
I had to do to fix my smoking turbo.


Tapadatass

[TiGraySpeed6]

I have an all metal PCV valve from a twin turbo supra for this exact purpose.
(~$1.50 from advance auto, all metal construction and a bullet proof, long-lasting reputation)


However the combo punch of 900 RPM idle, bnoon bolt and Rotella 5-40 has dealt a blow to my smoking issue. Next long weekend I will also be rebuilding my ~62K miles K04 to install new seals as well. Rebuild kit runs about $50, and should take longer to get it out of and/or back into the car than to do the actual rebuild.

[BigRedSpecial]

Interesting idea... I haven't had any smoking issues yet, but wouldn't this also cut down on the amount of crap being dumped into the manifold?

[06Speed6]

Just so that noobs know, krankvents are not pcv valves. You still need a pcv with them and the extra restriction of having two valves on an already poor vacuum source probably negates alot of the benefits.

[EL F00LI0]

Subbed for some good info.

Sent from my BlackBerry 9300 using Tapatalk

[RaceBuilt]

This vent situation is alight but not the correct way to fix the smoking issue. The two main reasons to have a catch can are, #1 to catch oil blow by from the motor caused by excessive pressure. #2 to free up pressure from the block so you can make more reliable HP. What a lot of people dont realize is a lot of pressure builds under the pistons causing ring failure. In many pro drag cars, they add a vacuum pump plumbed from the block to remove added pressure caused by the forced air in the combustion chamber. There is not reason to plumb it back into the intake tube at all. I'll put up some pictures of what I'm talking about later today. Say what you want about this but I've had years of experince in this matter.

@IshiKage

Originally Posted by mczimer Ok I know there are threads on Krankvents which are even more extensively debated but I'm trying to bring this concept more to the forefront of the discussion so that a larger percentage of our forum members can understand what's going on with our PCV valve and the smoking turbo issue. I have attached an MS Paint diagram of how the flow is with our stock system. As you can see from the diagram that shows flow while NOT under boost pressure, the vacuum produced in our intake manifold, pulls vapors out of our crankcase through the PCV valve. Air rushes in through our valve cover vent to replace the air that's being sucked out of the crank case. As a result, there is somewhat of a vacuum on our crankcase but often not strong enough to allow draining of oil out of our turbo lines thus causing smoking. In mockup #2 that shows the situation while under boost, our crankcase PCV valve is now shut since flow is only one way and that is OUT of the crankcase through the PCV valve. Our intake system, ahead of the turbo is mostly not under vacuum but under boost, when the turbo is sucking air in, a vacuum DOES exist within our intake system, whether that be a short ram intake, cool air intake or stock airbox. This vacuum is then pulling vapors out through our valve cover and back into our air intake system. Summary, both under idle/vacuum conditions and under boost, there is always a source of vacuum on the crankcase BUT HERE IS THE PROPOSED ADDITION: While the car is at idle, that's when we start to have smoking turbo because the vacuum flow to the crankcase ends up being too weak, most likely because air is so easily flowing BACK INTO THE CRANKCASE through the valve cover opening. If we install a check valve or just another plain old PCV valve here, allowing air to only LEAVE the valve cover, we can achieve the following: 1)Oil vapors are still vented into the intake because the added valve will allow vapors to EXIT... 2)Since flow is only one way, and that's OUT of the valve cover, a much stronger vacuum is maintained AT ALL TIMES within the crankcase. 3)Oil drainage out of the turbo at idle should be much more efficient in the presence of higher vacuum. 4)Sealing of piston rings enhance in the presence of a steadier vacuum. 5)A LOT LESS WATER being pulled into our crankcase and then into our catch cans. As a result of air NOT being pulled steadily in through our valve cover port, there won't be the constant supply of moisture that precipitates out into the crankcase/oil catch can. This should help reduce that hideous sludge that we've found, caking up in our catch can and lines leading to the catch can. Remember the peanut butter as some of us call it? So my question is, does anyone see a problem with this? I think someone mentioned in one of the threads at one point, perhaps on the mazda6club, that it wasn't good to have too much vacuum in our crankcase but not sure if that's going to be a problem with our cars since it's kind of weak in the first place. I realize that this touches on the concept of the usage of KrankVents but in isolating out just the junction between our valve cover and the intake system, I think this may be a trouble spot where we lose a lot of our vacuum to the crankcase, at idle. Thanks for staying with me on this long post. I think we may have something here that could improve our ill-designed PCV system.