iBuildRacecars Subaru Oil Separator for EJ20/25 Applications

This high-performance air-oil separator (AOS) kit is engineered for optimal efficiency. Featuring a triple-pass system with precisely designed diameters and cross sections, it effectively removes various sizes of oil droplets. The AOS mounts directly above the main crankcase vent, between the intake manifold and the TMIC, providing a clean appearance with minimal hose routing. As a true AOS, it drains oil back into the block, eliminating the need for manual emptying. The spiral baffle design includes small ridges to collect oil, keeping it out of the laminar airflow and ensuring effective drainage. The unit is easy to maintain, with tool-free disassembly via the top thumb screw for periodic cleaning.

Compatibility:

Drive by Wire:

• 2004 - 2021 STi
• 2006 - 2007 WRX (2008 - 2014 WRX can work if updated to the STi intake manifold)
• 2004 - 2008 Forester XT

Drive by Cable:

• 2002 - 2004 WRX

Works with a lot of of other vehicles with EJ20/25 engine swaps that utilize the OEM STi or WRX aluminum intake manifolds.

Key Benefits:

• Never needs to be emptied
• Short hose routings for a very clean install
• Carbon fiber outer housing tube for a high performance look and feel
• Retains factory PCV functionality
• Triple pass system for the most effective droplet separation
• Tool free and easy to clean assembly

Included in the kit:

• AOS01 Assembly
• AOS01 Mounting Bracket
• All Required Hoses and Hose Clamps