Ferocity02

iTrader: (59)

I'm looking to add a check valve to the drain of my oil catch can. When the engine is off and there is no vacuum inside the catch can, the check valve would be open and let the contents of the catch can drain out (back into the oil pan for example?). But once the engine is running, the vacuum inside the catch can would close the check valve, preventing anything from draining out.

Seems pretty simple, but all check valves I've used take some pressure to be opened. I haven't seen any that are "normally open". Perhaps it has a different name?

Also, a side question, anyone know if it's better to have the catch can under vacuum? In other words, is it better to put the PCV valve (external valve) between the intake and the catch can, or between the catch can and the valve cover. I'm curious if it makes a different in regards to oil separation ability.

This is not specific to my truck, it is a general project I'm working on for a different car.

Thanks

TrickTurbo

iTrader: (12)

You need an electric solenoid.
A "low amp" draw normally open 12volt small solenoid.
Connected to keyed 12volt.
Key on its closed.
Keyed off its open.

Thinking of draining back to the pan?

Ferocity02

iTrader: (59)

Was hoping to avoid an electrical solenoid.

I was just thinking about PCV valve that seals pretty well in reverse (might be hard to find). Many of them don't have springs so they would flop open without any air flow. Gravity would help it open too.

Yes, draining back into the pan would be ideal. Or drain into another reservoir, or just onto the ground. This thing collects a lot of moisture so the can fills up more often than I care to manually empty it.

Atomic

iTrader: (42)

If you can find a check valve with a very low cracking pressure the weight of the oil above it should open it...

TrickTurbo

iTrader: (12)

Hmmm

Really you don't need any check valve.

This should work.
Passenger side VC gets a breather.
Pcv at driver valve cover -> catch can -> one way check valve -> intake.
Bottom of catch can route small hose to oil pan.

Check valve needs to allow vacuum pull on through catch can.

This way while under normal driving your pulling vacuum on valve cover and crankcase.
When in boost one way check valve closes. No boost psi to VC or CRANK CASE.
Crank case vents through passenger breather.

No mess on the ground.

Ferocity02

iTrader: (59)

Any idea where to find one?

By my calcs, if I were to put the check valve 18" below the catch can, it would need a cracking pressure of 0.56 psi to open (assuming the drain line is full of mostly oil).

GMCtrk

iTrader: (27)

Why not just have the line going from the valve cover (or whereever you pull crankcase oil/gas from) above the level of the engine? Mine makes an inverted U shape so it's impossible to drain back.

Ferocity02

iTrader: (59)

I see what you're saying. My concern would be under normal driving, air would be entering the catch can through the drain at the bottom of the can. If there is oil in the can, the air entering through the drain would come up through this oil, tossing it all about inside the can and probably turning some of it back into vapor where it would exit it can and go into the intake.

TrickTurbo

iTrader: (12)

Msybe. Using a smaller hose would limit that air coming up. Since the larger line would allow that hose to pull easier. Also oil/liquid would always trying to go down.
Worth a try. .

The one way valve with you math would work.
But I think you would want a lower breaking psi.

Check will still need to be near intake. So your catch can will not see any boost.

Ferocity02

iTrader: (59)

Found some low crack pressure valves on McMaster, with cracking pressure of 0.3 psi: 7775K11

Back to your idea, you would want to place the PCV valve between the intake and the catch can or else the air getting sucked into the can from the drain line wouldn't be regulated.

I'm trying to keep the drain line large so it doesn't get clogged, thinking 1/2" or so.