View Full Version : PCV Ventilation- information

11-10-2005, 10:16 PM
PCV=Positive crankcase ventilation (aka, all the junk from the crankcase gets recirculated through the intake manifold so that little bit of exhaust that has unburned fuel gets burned up to keep emissions down).

But, that's not the only reason for it.

Some info from LCO:

You guys that are for the PCV all bring up good points, but the reason anyone wants to do this is because they think it will increase performance. The truth is though, that it will decrease performance. PVC, beeing a positive ventalation system creates a small amount of vaccuum in the crankcase. What this does it reduce pumping losses as the crank and pistons need to move less air in the crankcase when they spin (remember the back of the piston moves just as much air as the top does). PCV also promotes ring sealing as it helps to hold the rings to the bottom of the ringlands. You'll notice that any race car that runs a wet sump system will have some sort of PCV (either to the intake or the exhaust). Dry sump cars don't need them as the sump pump creates quite a bit of vaccuum on its own. You'll never see it vented to atmosphere.

So, having PCV is good for performance and helps the enviornment.

No PCV is a possable health hazard, can make your engine bay messy, is bad for performance, bad for the enviornment and is illegal (it's a federal crime to remove any emissions device from a vehicle operated on public roads per the Clean Air Act).

There's the pros and cons... you make the choice.

So those of you looking to put a breather on the intake manifold, and release the crank case ventilation, these are the reasons not to mess with the engineering :D

11-10-2005, 10:22 PM
For Your Reference:

Note: The Arrow is pointing to the other end of the tube that goes into the PCV Valve. Airflow goes into the intake manifold.

11-11-2005, 04:14 AM
I can't see how you can put a breather filter on the PCV valve. When the tube isn't hooked up the car won't stay running.

11-11-2005, 07:56 AM
PWT had one on there for a while.

I didn't have that problem when i injected seafoam into it....

Why wouldn't it stay running?

11-12-2005, 04:47 AM
There are some vaccume hoses that, when unplugged on the EJ22, prevent it from running properly. It'll stall after starting.

11-12-2005, 07:56 PM
that isn't the case with the PCV valve.

11-13-2005, 02:57 PM
I believe what you are referring to, Reason, is the idle air bypass valve line.

If you disconnect that, then the engine (at idle) will get no air, and choke.

11-13-2005, 08:03 PM
faux-performance... and lack an opinion


11-13-2005, 08:08 PM
faux-performance... and lack an opinion


don't remind me of that BS....

12-18-2013, 10:08 AM
I can't see how you can put a breather filter on the PCV valve. When the tube isn't hooked up the car won't stay running.
have been running a catch can made of an old pop bottle and bathroom culked old fuel hose to connect it all, it is not even air tight lol. i have been running it this way for over a year with no problems what so ever...

12-19-2013, 08:20 AM
subd for later

12-19-2013, 04:54 PM
subd for later

What? Why? This is an old thread that got randomly bumped, it's not like you need to reserve your place in line.

12-19-2013, 08:56 PM
hi mark! been a while!

12-19-2013, 09:44 PM
Yes it has! Looks like you have 2 Subarus now, good on ya!

12-19-2013, 09:59 PM
actually have to fix my signature.

i now DD a 2013 Honda Odyssey. Wife drives the 09 Forester. Bought a 98 Ducati 916 for a toy. Most significantly, I have a 3-yr old, and 6-month old twins. thus the Odyssey. :-)