Originally Posted by Ducked
Anyway, core point, about keeping it hot to separate the water and fuel vapour, was interesting, though in a non-race context the oil lost in a catch can probably isn't a big deal.
I wonder if you could achieve a similar effect with insulation. Stainless steel vacuum flasks arent very expensive.
My car has a factory oil-air separator unit. Not as fancy and maybe not as effective as an off the shelf catch can, but enough to recover a bunch of oil mist that gets blown out the breather ports and return it to the sump. It's deliberately mounted right against the block, and the hoses to the turbo inlet and the manifold also hug the block and are wrapped in insulation to keep them hot. When I've cleaned the system recently, there was a light layer of sludge right where it connects to the turbo inlet where it will be coldest, but only a slight oily film everywhere else in the system. Its obviously significant how much oil it catches, since manufacturers won't go to such lengths and expense without good reason. The system only clogged once at 150k miles most of which was on 90s/2000s conventional oil, and since then only that light bit of sludge at the cold areas has developed.
While insulation around a catch can might work for extended use, without external heating, the can may not warm up on the same cold short trips where it will be collecting the most moisture and fuel for a daily driver (cold engine running rich with increased blowby until it warms up). If there's some liquid in the can already, that adds to the mass that must be warmed by the trickle of incoming air and vapor. Placing the can against the block or running a coolant jacket will insure it rapidly reaches temps where fuel and water vapor flash off from the captured liquid, even on shorter trips of a few minutes.
