hate to sound dumb but i work for audi and never heard of a oil catch can what is it extactly (i know it catches oil)

 

its a canister of some type that collects and stores oil.. generally used in-line for the PCV line.

you see, the PCV is meant to only allow gasses through it to head to the intake manifold.. however, oil often follows this path as well. the catch can, makes it so the oil will fall down into the can, and only the gasses continue towards the intake manifold.

now, thats for a non-vented catch can, obviously, since it deals with vacuum to help pull the gasses to the intake.

what exactly a vented catch can is used for, im not real sure.

 

That's really only for a turbo car right?

 

Umm not exactly - a catch can collects oil and and open design vents blow-by to the atmophere - your crankcase ventilation involves the PCV and the breather. The pcv allows unburt hydrocarbon vapor to go into the intake manifold instead of being released into the atmosphere and is fully open when vacuum is low (high load). The air passage progressively gets smaller as vacuum increases and is the smallest at idle (high manifold vacuum) - this controlled by a return spring usually. It is true that it is a check valve and allows for flow in only one direction. The breather acts to regulate your crankcase pressure by venting to atmospheric pressure (zero vacuum, zero gage) and lets the air flow into the crankcase when the pcv is fully open. If the breather was truly vented to the atmosphere the EPA would have a fit - so they vent it back to the air cleaner box where the pressure is always fairly close and for all intensive purposes IS atmospheric pressure. This way any hc's are run back into the engine and hopefully combusted. A catch can is nice because then you don't get any oil that makes it way back through pcv or breather in your intake manifold or airbox. I have a MAJOR problem with this on my car and have considered hooking up a closed catch can like you are describing - which is basically resevoir in line of the pcv system to trap oil and keep it out the manifold while still allowing hc's to make their way into the engine. The open system just vent has a can that vents everything to the atmosphere and is really not legal although nobody is really gonna get you on this one. The thing is with the open system you will have a decrease in your fuel mileage. Turbo cars may find these more useful because of the higher cylinder pressures - you get more blow-by and more crankcase pressure and possibly more oil finding its way into the intake manifold where it shouldnt be. I'm glad someone said something about this cus I really gotta hook one up on my car...hope that clears everything up.

 

[font="Tahoma"] Hi Iblackneon, this is my first time on this forum. Go to allpar.com and find forums/tech help, schroll down to neon and search for "who got oil in their intake" and read and see pics. This might help with catch cans (not good in below freezing conditions).
Kayakman