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Has anyone tried this? I am tackling crankcase ventilation (parts incoming) with 12AN lines from cam covers to a 3 liter catch can but as far as a sump vent not in a position to pull the engine (again) soon so I had this idea of simulating a sump-vent by either taking over the dipstick tube or welding a "Y" into it and running that to a small dedicated catch can vented to atmo. I've noticed in the Evo community such a product exists (dipstick tube with an AN fitting off the side) so it doesn't seem completely crazy. There is surprisingly little info out there on the web regarding this stunt.

The tube appears to enter the pan quite high up with several inches clearance to the oil line, so in my mind I don't see how it could be much different than a dedicated sump vent except that it is much smaller in size. But I figure some ventilation is better than letting it all exit through the cam covers (which I would think would still allow excess oil to travel to the head along with the sump pressure).

The thought of oil coming up the tube did occur to me so I also thought if I ran that line into the bottom of the catch can, anything coming up could automatically run back down when engine is off or when sump pressure is naturally low. Otherwise, would run in to the can normally, filter to atmo and drain via remote hose later.

Later on when I'd pull the engine, it would be extended sump with dedicated AN fitting for the sump vent.
 

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The sump vent via dipstick does something, just not a lot because it's small as you have identified.

Also, you don't want to vent to atmosphere. Not just because of the fumes it will generate but because the pre-turbo vent hose generates a slight vacuum on boost that helps evacuate the crankcase.

You want to run the PCV side (which has a PCV valve) to the post-TB vacuum source. The PCV valve is there to prevent intake boost pressure from filling the crankcase. On boost only the fresh air supply is used to suck the crankcase pressure out of the engine. You want your catch can to filter the air coming out and the outlet to feed to the pre-turbo inlet to help crankcase pressure move out of the car.

If you want to run the dipstick vent or another crankcase vent you probably want to make sure that it doesn't become a vacuum leak when the vacuum side of the PCV system is functioning.
 
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