Draining catch cans.

[Fu Manchu]

Is there a reason why crank case gases are vented into the intake, rather than venting into the sump?

Also, why not a catch can that drains back to sump?

 

[VS_Pete]

I think there is a thread somewhere I`ll have a look this afternoon

 

[Deuce]

The crankcase is where it is venting from, so pointless making a circle.
Intake has a vacuum so helps draw pressure.
Caught oil mist is a murky crap worth nothing more than throwing.

 

[_R_J_K_]

^^^ Hit the nail on the head, pointless circle.

The PCV system also needs the the vacuum/suction of the intake to work properly (vent to atmo is just wank really and doesn't work as well). If there's anything flammable in the gasses that come out they go straight back into the engine too. As for drain back, you shouldn't have so much oil coming out that it needs to drain back, and if you're filling catch cans up you've got issues.

 

[Fu Manchu]

I only got thinking of the question because I watched a video featuring a Hyundai motor which vented back to the sump? Maybe they got their info wrong?

Thanks for the replies folks

 

[Mattricho]

I think you can use a one way valve set up to vent back to the sump.
So car running the vacuum closes the valve then when you turn off the car there’s no vacuum so to valve opens emptying the catch can.

 

[_R_J_K_]

I only got thinking of the question because I watched a video featuring a Hyundai motor which vented back to the sump? Maybe they got their info wrong?

Linky? Got me interested. The only thing I could picture plumbing back is a turbo oil return line. Not really PCV - positive crankcase ventilation - if it's venting gas to the sump.

 

[Darren_L]

the entire concept of the PCV is to relieve/vent pressure and undesirable fumes/vapours away from the crankcase.
If you vent the pressure from the crankcase back into the crankcase, you have completely defeated the purpose.

Ideally you would drain the catch can out and dispose of it as the oil captured will contain various contaminants from the crankcase including moisture. However, there is no reason why you can't drain the catch can back into the sump. It's only recycling what came from the crankcase anyway, no different to what would end up in the sump if you didn't run a catch can