Radium Engineering AOS-R Kit with Master Cylinder Brace

Perfect Fit for Your Subaru WRX | Forester XT (2014-2021)

If you’re a Subaru enthusiast, you know that high-powered modified engines can sometimes produce a bit too much blow-by oil and gas. That’s where the Radium Engineering AOS-R Kit comes into play! Unlike a standard catch can that can fill up quickly and leave you wanting more, this Air Oil Separator (AOS) kit is designed specifically for your Subaru WRX or Forester XT, ensuring that all that excess oil and pollutants stay out of your intake pipe, manifold, turbocharger, and intercooler—no matter how hard you push your engine.

How It Works

The beauty of the AOS system is that it returns what it collects straight back into the oil pan, which means you won’t have to worry about servicing it regularly. Plus, it features a built-in heater that prevents water from condensing inside the AOS. Since water is denser than oil, there's also an integrated water trap at the bottom perimeter of the can. This clever design keeps any water that might sneak in from descending into the oil pan. Instead, it gets trapped against the heater, where it eventually boils away, keeping your system clean and efficient.

Key Benefits

• Boosts fuel octane and improves engine performance by providing cleaner inlet air.
• Prevents oil buildup in critical areas like the intake, intercooler system walls, throttle body, and intake manifold.
• Reduces hydrocarbon emissions for a greener drive.

Installation Made Easy

Installing the Radium Engineering AOS kit is straightforward for your 2015+ Subaru WRX. It mounts on the left-hand side of the engine bay, right by the brake master cylinder. The outlet of the AOS is cleverly plumbed back to the turbo inlet pipe, creating a completely sealed system. To make it all fit perfectly, the AOS mounts to the Radium Brake Master Cylinder Brace, which is a must-have for installation. You’ll also replace the PCV valve with a custom machined straight-through adapter fitting, ensuring that any oil collected in the AOS drains back into the engine block smoothly.

Important Note

• If you’re driving in freezing conditions, Radium Engineering recommends adding insulation sleeving (not included) over any hoses exposed to cold air. This will help prevent water condensation from freezing and potentially clogging your hoses.

Compatibility

• Subaru WRX 2015+
• Subaru Forester XT 2014-2018

Ready to keep your Subaru running smoothly? The Radium Engineering AOS-R Kit is the perfect addition to your setup!