digs Posted February 5, 2014 Report Share Posted February 5, 2014 Ok, not sure if I have completely misunderstood PCV.... On my 3sfe I have a connection from the valve cover to the manifold. Now, under vacuum this sucks the air out of the crankcase into the manifold to be burnt up again, yes? So I have a one way valve on this so under boost conditions, as the manifold is positive, it stops pressurising the crankcase. And I also have a breather tube, from again the valve cover, that connects to the air box. This now connects to the cone filter piping before the turbo. Now..I have an oil catch can, but I have put this on the breather tube. That doesn't sound right reading what I have written, shouldn't it be put between the valve cover and manifold ? The breather tube....under vacuum it pushes out air. so connected to pre throttle, that is just going to increase the amount of "suction" and pull more air out of the crankcase. So in boost situations this is now pulling out air and stopping over pressurisation. So reading THAT, I should out the catch can here. Ugghhh. What I am being to dense to understand here! 2 catch cans ? Breather just out to a mini filter ? Breather supplies fresh air which is then sucked out by the manifold valve...if so why does it puff out air when idling rather than drawing air in? someone put me out of my misery. It all works, but my catch can is arse-about-face? Link to comment Share on other sites More sharing options...
dublet Posted February 5, 2014 Report Share Posted February 5, 2014 Is this useful? NA PCV explained: http://www.sr20-forum.com/information-library/34413-crank-case-ventilation-fully-explained-naturally-aspirated-edition.html FI PCV explained: http://www.sr20-forum.com/information-library/44727-crank-case-ventilation-fully-explained-turbocharged-edition.html Link to comment Share on other sites More sharing options...
digs Posted February 5, 2014 Author Report Share Posted February 5, 2014 (edited) Thanks It is...kinda.....as it shows the catch can between the valve cover and the crank case, with a second pipe to the intake "boot", whereas mine is on the pipe to the intake "boot" as there is no external connection between valve cover and crank case to put the catch can. Maybe it's just not appropriate ? EDIT: actually, that is just an internal things isn't it. However, will read those links, thanks for the help Edited February 5, 2014 by digs Link to comment Share on other sites More sharing options...
dublet Posted February 5, 2014 Report Share Posted February 5, 2014 There are some other diagrams in the links that show a second catch can between the intake plenum and valve cover. Some also show some breather filters. So two catch cans is not out of the question at all. Link to comment Share on other sites More sharing options...
digs Posted February 5, 2014 Author Report Share Posted February 5, 2014 the manifold gets oily whereas the breather pipe seems ok, only a drop of oil caught. I think two makes more sense.... Link to comment Share on other sites More sharing options...
_Chris_ Posted February 5, 2014 Report Share Posted February 5, 2014 The quantity of blowby gas is related to how hard the engine is working. Light throttles, when the manifold is at vacuum, there is very little blowby so mostly you get fresh air going in the breather, through the engine, and out via the PCV valve to the inlet manifold. The flow is very small, so very little oil is carried in the air, hence no need for a catch can. On boost, the PCV valve is closed and the considerable quantity of blowby gas goes out through the breather taking with it oil mist from the sump. The separators in the cam cover plus the catch can remove as much of this oil as possible to return it to the sump. The reason for having this 'double breather' system is that under 'cruising' conditions (most of the time on a road car) it keeps a supply of fresh air passing through the engine, removing the nasty chemicals in the blowby gas. Link to comment Share on other sites More sharing options...
digs Posted February 6, 2014 Author Report Share Posted February 6, 2014 Thanks, read through the line as well, and makes much more sense, the two effectivelly switch. Found it quite interesting about setting up vacuum pumps/using exhaust as a vacuum to pull away the gasses. Not that I will do either. cheers guys Link to comment Share on other sites More sharing options...
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