Ventilation in valve cover?

[E30FETT]

I'm curious about what kind of ventilation this is and why is it just not going straight into the valve cover instead of going into a plastic cover inside the valve cover?

http://i44.tinypic.com/rh93rk.jpg

[vpilarrt]

If the valve cover was not ventilated it would become pressurized due to leakage around the valve seals and blow out the valve cover gasket. The tube from the intake boot to the valve cover applys a vacuum to keep this from happening. The plastic part is there to act as an oil seperator so you don't pull a bunch of oil into the intake.

[E30FETT]

If the valve cover was not ventilated it would become pressurized due to leakage around the valve seals and blow out the valve cover gasket. The tube from the intake boot to the valve cover applys a vacuum to keep this from happening. The plastic part is there to act as an oil seperator so you don't pull a bunch of oil into the intake.

Okay, I can't really understand why the hose has to go to the intake. Why can't it just be hanging loose in the air?

[oldmann]

Vacuum to valve cover also applies vacuum to crankcase. Without the Vac. vapors, smoke (blowby) remain in engine.

You could plug the intake hole, and run a draft tube down close to the bottom of the engine, not as effective as vacuuum.

or run a catch can in line to catch the oils being sucked into intake.

[torell]

i think it's not the matter of vacuum being more effective but just a environment protection from oil vapours getting into atmosphere. The way it is from factory the vapours are burned with air&fuel. Minus of this solution is the sludge in intake, therefore using a catch can can do the trick. Guys going for FI go with a filter on cover outlet or just a pipe under engine.

[E30FETT]

i think it's not the matter of vacuum being more effective but just a environment protection from oil vapours getting into atmosphere. The way it is from factory the vapours are burned with air&fuel. Minus of this solution is the sludge in intake, therefore using a catch can can do the trick. Guys going for FI go with a filter on cover outlet or just a pipe under engine.

Okay. What is FI?

[kamotors]

Vacuum really helps the engine out, you'll notice cars without the vacuum will usually smoke on over run and idle rougher in my experience. Also turbo cars run a bunch smoother with the vacuum routed to the turbo inlet vs. the atmosphere.

[vpilarrt]

FI = forced induction = turbo or super charger

[Dj Buttchug]

Vacuum really helps the engine out, you'll notice cars without the vacuum will usually smoke on over run and idle rougher in my experience. Also turbo cars run a bunch smoother with the vacuum routed to the turbo inlet vs. the atmosphere.

hmmmm. ive been running mine to atmosphere for a while now... I cant see how sending boost pressure into the crankcase is a good thing

[PNWDan]

hmmmm. ive been running mine to atmosphere for a while now... I cant see how sending boost pressure into the crankcase is a good thing

He said turbo inlet not outlet. The inlet is the vacuum side. Nobody runs boost pressure into the crank case. You'd blow it up.

[Dj Buttchug]

He said turbo inlet not outlet. The inlet is the vacuum side. Nobody runs boost pressure into the crank case. You'd blow it up.

The inlet is not vacuum at all. The turbo inlet pulls air from atmosphere. the only place there is vacuum is somewhere behind the throttle body. WTF are you talking about...

[bmwman91]

I had mine vent to atmosphere for a few weeks once. I kept smelling exhaust gas and oil so I replaced the broken hoses that prompted me to open it up in the first place.

If someone has a good catch can solution, I am totally open to see it. The oily intake gunk is t3h suck.

[wazzu70]

The vacuum is beneficial to the engine, its not just an emissions thing. The vacuum helps the piston rings seal against the cylinder walls through the pressure differential it creates.

Many race teams go to extra lengths to maximise crank case vacuum with their dry sumps because it can increase power a noticable amount.


Buttchug, the way to use this with FI is to use an inline check valve so you do not pressurize the crank case.

[Dj Buttchug]

Buttchug, the way to use this with FI is to use an inline check valve so you do not pressurize the crank case.

This. Basically what you need is another brake booster check valve which only allows for vacuum and not boost.

Currently my crankcase vents to atmosphere, not because thats how I wanted it but because I have no where to run it. MAP sensors take up the stock location ports amongst other things.

In for anyone with better insight on this.... Kamotors, Describe your routing set up on the m20. Applying to m42 will be the same. My car has a brand new engine it doesnt smoke but I do have some minor idle issues.

[wazzu70]

Well mine is routed to atmosphere too because I have not got around to makimg a proper solution yet :) So dont feel bad.

I plan to route from the VC to an oil seperator/catch can, then back to the inlet tract. Im not planning on venting the can to atmosphere.

You can tap into any point from the IC to the throttle. Probably even behind the throttle too in the intake plenum. You will either need to weld a bung to your IC piping and thread in a barbed fitting for the hose or drill and tap the intake manifold.