ForcedInductionX2+

I would like some suggestions as to whether to go with a single catch can with dual valves or two single catch cans. Most of the manufacturers have a clean side separator which appears to have the possibility of allowing oil back to the intake manifold,with the dual valve system. would two single valve systems be more sufficient to remove oil from the intake system, or does this clean side separator remove oil also.

vozaday

Dual valve IMO, the clean side separator removes oil also.

phantomblackgto

Dual valve. If you run two separate cans, you would still need a fresh air source. I guess you could eliminate the check valves, but then you run the risk of sucking the can contents back through the lines. From what I've seen with the CSS, you might get a very slight pull through to the airbox, but it's not going to be enough to make it all the way to the intake. You really just want to keep clean in one side and dirty out the other.

ForcedInductionX2+

so is the clean side separator used to allow air into the valve cover from the air intake?

phantomblackgto

Yes. That provides fresh air in to replace the dirty air the PCV is clearing out (or at least that's how it's supposed to work). The PCV uses vacuum from the intake manifold to draw out the blowby. Unfortunately, in stock form though, when under boost, the IM becomes pressurized and the PCV valve actually closes and doesn't evacuate the blowby. The pressure in the IM will actually push back through the clean side which, in stock form, is connected to the driver side turbo inlet pipe. The advantage of the dual valve setup in combination with a CSS, is that it taps the turbo inlet pipe(s) to provide vacuum for the PCV when under boost so it will evacuate whether you're in boost (via the turbo inlet pipe(s)) or not (via the IM). Some drill the passenger side turbo inlet pipe as well as using the existing barb on the driver side to get as much vacuum as they can while others (including myself) just use the driver side only to avoid drilling the passenger side (not getting as much vacuum to help the PCV do it's job, but results from just using one side seem to be pretty good).