To catch any blow by oil from the valve cover vent tubes before venting into the intake before the turbo. So far at 12 psi or so, I have yet to see any real amounts of oil in this catch can. But it will be needed when I crank up the boost later on.
Paul, what are you running there? Your sig says 2.0 liter, so you swapped the EJ20T or what? Or am I being stupid and that's a GD WRX... Whatever the case, what turbo/tranny/times are you running, as that's one nice looking engine, and very nice with TEC III.
I am running a bored out 2.5 with forged pistons, rods, knifed and balanced crank and O-ringed block. The top end is stock and that is indeed the twin coil pack from a TEC 3 unit. As for the turbo set up, well that is a Ludespeed Stage 2 kit. But most of the origional "stage" is not there any more. It's more like a stage 4 if you factor in the engine internals and engine management. All for the unbelievable low price of one dollar... I wish