Air-oil separator for extracting oil from engine blowby gas

A method of separating oil from engine blowby gas comprising:

• venting blowby gas from the crankcase of an engine and into an air-oil separator;
• flowing the blowby gas through a separator volume defined by the air-oil separator, the air-oil separator having an interior surface abutting and surrounding the separator volume;
• and
• venting the blowby gas from the separator volume into an intake manifold of the engine;
• and
• wherein the interior surface of the air-oil separator has a surface roughness (RA) of greater than about 75 microns to promote the efficient separation of particulated oil from the flowing blowby gas.

An engine assembly comprising:

• an engine including an engine block, a cylinder head, an oil pan, and a cylinder head cover, the engine block and oil pan partially defining a crankcase;
• an intake assembly including an intake manifold, the intake manifold being in fluid communication with the combustion chamber;
• and
• an air-oil separator disposed within a volume partially defined by the cylinder head and cylinder head cover, the air-oil separator defining a separator volume and further defining an inlet and outlet in fluid communication with the separator volume, the inlet of the air-oil separator being in fluid communication with the crankcase, and the outlet of the air-oil separator being in fluid communication with the intake manifold;
• and
• wherein the air-oil separator includes an interior surface that abuts and surrounds the separator volume;
• and
• wherein the interior surface has a surface roughness (RA) of greater than about 75 microns.