Who's running a catch can?

wstar

The pic *does* look sort of like that, but it could be that the pic is deceiving, or that there are some additional one-way valves at various points in his hoses, or perhaps the setup is simply ill-conceived, I donno. Most likely the rather expensive and nice-looking setup in that pic works correctly, but I'd need more details about the components to tell you exactly how.

In any case though, your translation to two simple cans in your hose map drawing isn't going to work. The two PCV-related outlets on each valve cover are not both outbound. On each side of the engine, one is outbound from the crankcase, and one is inbound fresh air. The factory setup is that, separately on each side of the engine, one hose flows outwards from the crankcase to a manifold vacuum inlet, and the the other hose flows inwards from filtered intake air into the crankcase. At least the vacuum-connected ones have PCV valves on them, I'm not sure whether the fresh-air-connected ones have a valve buried in there somewhere (or perhaps just some foam or something).

So to run a dual-can setup, the normal way would be to splice one can into each of the vacuum<-crankcase lines. Or you could set up a single can with 4 connections the same way. Or you could do what I did and use a single can with two connections to cover with both sides, by tee-ing the pairs of vacuum and crankcase lines together (my instructions are M370-specific, but the same general idea could be done on the stock manifold): DIY - Oil Catch Can (w/ M370 + Batt Reloc).

If you want to catch oil in the fresh air side (which, tbh, I'm not really sure is worth it. It normally flows the other way, *into* the oily area, but I guess under various transitional conditions it must backflow a little), you probably would have to have a separate chamber for that, either as a combined setup or again one per side.

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