PCV & catch can idea, will it work?

[crazyboost]

Before i get one of these about over-discussing this popular topic or not searching the forums. ive been reading about this on this site amounst others for several hours now. After several boost leak tests its apparent that my pcv is leaking like many other dsmers on the forums. Ive read tons of debates on emissions vs crankcase ventilation aspects of the pcv valve functions and read the pros/cons of catch cans.... I know that the crankcase has pressure and it must be relieved somehow whether via pcv or the hose going from passenger side of valve cover to the intake/turbo inlet, also the unburned hydrocarbons and acid fumes must be removed from the crankcase valvecover so that they will not corrode parts or turn your oil into a sludge. So i have two basic options, to buy another pcv valve and hope it works for a while (both autoparts stores and dealers pcv's have been known to not work or not work for very long), or to ditch the pcv and go with a catch can. Now with the catch can there isn't a vacuum source to suck all gases out of the valve cover there is just a place for the excess oil and pressure to go. My question is if i left the hose going from the side of the valve cover to the turbo intake, would the turbo-created vacuum be enough to get rid of all my unwanted fumes from my valve cover?
So basically I would block the port going to the pcv on my intake manifold. Gut my pcv and run that to a catch can with a vent/filter on it. Then just leave my existing line going to turo inlet, but maybe throw a fuel filter on their to catch some oil that would be going into my intercooler.
All you pcv gurus out there, is there anything wrong with this setup? sorry if that was confusing and repetitive. thanks

 

[crazyboost]

Has anyone hooked there catch an up to the exhaust?

 

[tyger1]

Here i hope this helps.

http://www.roadraceengineering.com/instructions/catchcaninstructions.htm

 

[crazyboost]

Alright I have been doing more research and have a different idea now. Let me know if there are any problems with this or if anyone has done this. So my last idea wasnt the greatest because I dont think enough fresh air would be supplied to the crankcase. Now I would like to use the exhaust as a vacuum source (like all the muscle cars do). First I would take out the hose that goes from the side of the valve cover to the intake and replace with a filter. Then I would leave the existing pcv in place and run a hose from that down to my exhaust somewhere after my wideband closer to the rear of the car and tap it in there. This would help pull out some of the fumes in my crankcase. Then new air would be sucked in through the filter to replace the unwanted fumes. I think this breather filter is necessary because I dont want a total vacuum in the crankcase (it could cause problems with oil and bearings etc.), anyone agree or disagree? Would the pcv ever let any oil past it? I dont want oil building up in my exhaust or muffler. The purpose of leaving the pcv would be to not only block the oil form coming out of the valve cover but to not let any exhaust gases into the valve cover either. Mine right now leaks but not until about 12 psi, so i think i am ok with using that one. There is no way my exhaust flow would create 12 psi, especially with almost no back pressure in the straight thru 3" piping. Would there be enough vacuum in my exhaust (near the muffler) to pull out some fumes/pressure from the crankcase? Anyone want to comment on this idea or tell me why it wouldn't work? thanks

 

[MyBeatGSX]

Sounds like a good idea to me. This was actually discussed in the last PCV topic, so try to find that one.

The PCV valve will probably not work. You NEED a 1 way check valve. You don't want to pressurize your engine with exhaust.

I know this works because old guys do it all the time, but I don't really see how. How can the exhaust ever have vacuum? If it had vacuum then stuff would be getting sucked back through the muffler. That whole system is under pressure, that's why the exhaust shoots out of every open hole (exhaust leaks). I believe this exhaust PCV line has to be at the correct angle and that has something to do with making it work. So make sure you get that right.

 

[PieEyedPiper]

Sounds like a good idea to me. This was actually discussed in the last PCV topic, so try to find that one.

The PCV valve will probably not work. You NEED a 1 way check valve. You don't want to pressurize your engine with exhaust.

I know this works because old guys do it all the time, but I don't really see how. How can the exhaust ever have vacuum? If it had vacuum then stuff would be getting sucked back through the muffler. That whole system is under pressure, that's why the exhaust shoots out of every open hole (exhaust leaks). I believe this exhaust PCV line has to be at the correct angle and that has something to do with making it work. So make sure you get that right.

Where there is any positive pressure at all, there is vacuum (negative pressure).

Air in ==>==>===(exhaust piping)=====>======>== Air out

At least thats my understanding, this hold true for everything, your vacuum cleaner at home, and the clouds in your sky (high pressure zones/low pressure zones)

 

[crazyboost]

Isn't the pcv valve pretty much a 1-way check valve? Not trying to argue just curious. The only time it will open is if there is a negative pressure (vacuum) on the one-side of it. The exhaust will never have positive pressure as long as I cut the small pipe that will be welded into the exhaust at a 45 degree angle (slash cut). This will then point the opening of the pipe will then be parallel to the flow and pointing towards the rear, so gas will not be able to flow into it, but rather create negative pressure by flowing past it. this should definitely be enough to draw out some fumes from the valve cover. Im thinking of going with a 5/8" line and run it back into the exhaust right before the muffler. If the pcv valve won't work would this 1 way check valve block oil from entering the exhaust as well? Do you think it would be better to put it right where the valve cover is or closer to the exhaust? The only downfall i can think of putting closer to the exhaust is that some oil could get sucked into the line and buildup behind the valve, then it would either just sit in there or have to make its way out the exhaust. I think putting it where the existing pcv valve is would be the best. if not ill need a catch can i think. Thanks for the replies guys.

 

[PieEyedPiper]

Isn't the pcv valve pretty much a 1-way check valve? Not trying to argue just curious. The only time it will open is if there is a negative pressure (vacuum) on the one-side of it. The exhaust will never have positive pressure as long as I cut the small pipe that will be welded into the exhaust at a 45 degree angle (slash cut). This will then point the opening of the pipe will then be parallel to the flow and pointing towards the rear, so gas will not be able to flow into it, but rather create negative pressure by flowing past it. this should definitely be enough to draw out some fumes from the valve cover. Im thinking of going with a 5/8" line and run it back into the exhaust right before the muffler. If the pcv valve won't work would this 1 way check valve block oil from entering the exhaust as well? Do you think it would be better to put it right where the valve cover is or closer to the exhaust? The only downfall i can think of putting closer to the exhaust is that some oil could get sucked into the line and buildup behind the valve, then it would either just sit in there or have to make its way out the exhaust. I think putting it where the existing pcv valve is would be the best. if not ill need a catch can i think. Thanks for the replies guys.

Definitely got the right idea. But a check valve owuld be a nice piece of mind you know?
Also I would tap itno the exhaust after the o2 sensor, i ahve no proof it would make a difference, but in my head theres a chance to scew readings so I'd just play it safe.
Good luck.

 

[crazyboost]

Yea I know what you're saying about the check valve, just to be sure and I know how crappy of a rep our pcv valves have. So should i put it right next to the valve cover or use a catch can and put it further down the line. Anyone know if these things will block oil from going through them?
I plan on putting it pretty far down the exhaust close to the muffler. I figure the exhaust will have less back pressure at this point and still have equal flow to produce a nice vacuum. Also I dont want these fumes/gases going by my wideband 02 sensor (located about where the stock cat was), I'm not sure if the fumes would have any affect on my readings but i just want that piece of mind again.

 

[alex99gst]

Where there is any positive pressure at all, there is vacuum (negative pressure).

That is true, but the vacuum is at the inlet of the turbo and the air stays pressurized through the intercooler piping, and then out the exhaust.

 

[crazyboost]

So I think I have finalized my setup. I'm gonna order one of those kits that have two:
threaded slash cut tubes
check valves
breathers
grommets
It has two because i could only find kits for v8's

Then im gonna ditch the pcv valve, tap the valve cover for a 1/8" npt nipple send that to a sealed catch can with some steel wool or something in there to make sure the oil doesn't go down to the exhaust. Then run some 5/8" heater hose from the catch can to the check valve and slashcut right before my muffler. Also put a small breather filter on the passenger side of the valve cover. I'll let you guys know how it turns out in a week or so. And if anyone would like to buy the other half of my crankcase evacuation kit let me know and we can work something out.

 

[t0ny007]

Then im gonna ditch the pcv valve, tap the valve cover for a 1/8" npt nipple send that to a sealed catch can with some steel wool or something in there to make sure the oil doesn't go down to the exhaust. Then run some 5/8" heater hose from the catch can to the check valve and slashcut right before my muffler. Also put a small breather filter on the passenger side of the valve cover. I'll let you guys know how it turns out in a week or so. And if anyone would like to buy the other half of my crankcase evacuation kit let me know and we can work something out.

"The PCV effectively and simplistically takes out unwanted, harmful blow-by in your crank case and removes it via vacuum in the intake manifold. This feature is not in function under WOT. In fact once the intake manifold reaches 1psi, it is theoretically closed and not in use. Taking out the PCV system seems pretty dumb to me."
http://dsmtuners.com/forums/showthread.php?t=224901