Cobb Tuning LF Bypass Valve | 2015-2021 Subaru WRX / 14-18 Forester XT (745670)

Cobb Tuning
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2015-2021 Subaru WRX / 2014-2018 Forester XT LF Bypass Valve by Cobb Tuning

The C.A.R.B. Certified COBB LF BPV is a compact and lightweight by-pass valve that is capable of holding very high boost pressure without leaking. Its updated design reduces control volume by 30% allowing for extremely fast venting of boost when actuated. Innovative engineering and precision manufacturing result in a compact package able to fit in the confines of a tight engine bay. Due to the low weight of the components, the moving parts in the LF BPV have less inertia and can respond faster than heavier components in other bypass valves.

This updated design uses a Banjo-fitting vacuum port which provides 360 degree adjustability of hose routing. This results in a simpler install and less potential leak points than the NPT ports. This new design also includes a piston o-ring seal that is twice the diameter of the old design allowing more seal compression and reduced wear. Adjustability of the spring seat is no longer needed due to the updated spring and seal design which provides a 60% increase in clamping force at peak boost while maintaining similar operation at idle and transient loads.


  • 100% Billet Aluminum Construction
  • 100% O-Ring Sealing
  • Compact and very lightweight bypass valve


  • 100% Rebuildable if there ever is an o-ring failure
  • Reduces control volume by 30% allowing for extremely fast venting of boost when actuated
  • Holds high levels of boost without leaks


  • 2015-2020 Subaru WRX
  • 2014-2018 Subaru Forester XT

What's In The Box?

  • 1 - LF Bypass Valve
  • 1 - 6mm Vacuum Hose (3ft)
  • Zip Ties



  • Manufacturer Standard Warranty.

Customer Reviews

Based on 10 reviews

All I wanna do everyday now is drive around and listen to this bvp. And mainly in a low rpm letting off the throttle. Amazing flutter sound

A must have easy install

will add this to any WRX i have. minimal flutter to prove it is all business. super simple install and product looks & feels well made. i do not have any complaints about this cobb product.

Love the sound

I have been running this BPV for over 6 months and I cannot get enough of the Cobb Big SF intake and BPV sound. Also, the design is very high quality.

Ben Westfall

Me and my buddies all have different bpvs. And the Cobb is by far all our favorite. Amazing sound

Nice parts

Easy install, not plastic, and sounds good