Hi,
A question about the merits of simply venting the PCV to air versus an Oil Catch Can.
From what I can determine the Intake Manifold sucks air from the crankcase, so simply venting via a filter would not work unless there is enough pressure in the crankcase to push the gases/oil out. Even with some pressure in the crankcase it will not be as effective without the suction from the manifold.
So......
- is my understanding correct?
And if so....
- could simply venting cause a build up of oil/water in the crankcase? Which I would assume to b
e bad.
I'm not a mechanic, and have been putting off the job of removing the intake manifold to inspect/clean the valves for some time but given the findings in this thread and Roberts video I think it's time I did. The car has done 39k miles and I used a GDI valve cleaner through the intake at 29k and 34k miles, it will be interesting to see if this has had any effect at all.
Regards
The system is effectively sealed Mark, and negative crankcase pressure became "a thing" years ago, to contain crankcase oil droplets and arguably to inhibit leaks through the crank seals.My 1967 Midget had a primitive valve set above the inlet manifild, which was a shallow pan shaped metal casing which contained a rubber diaphragm. A pipe came direct from the crankcase into the edge of the valve, which fed vertically down into the inlet manifold between the twin SUs. The valve was kept open by a light spring, but when the manifild depression increased with throttle opening, the valve closed so that no vapours were drawn through. When the diaphragm got a pinhole, the valve fluttered, and it actually sucked oil into the inlet manifold and made a spectacular smoke screen.
The GDi system sucks from the crankcase into the inlet manifold via the narrow bore pipe, and from the cam cover into the inlet tract upstream of the throttle body via a wide bore tube. By disconnecting the pipes, the crankcase will not have negative pressure, but I really don't see this affecting the function of the engine.I tried a catch tank on the cam breather but it stayed clean. On the inlet manifold, space is difficult. Whatever you decide, I don't think it will make much difference, and as John mentioned, some of the deposits will come down the valve stems anyway.
