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XLE Bypass Valve

Cobb has evolved the bypass valve (BOV) to the next level with the XLE. Innovative engineering and precision manufacturing allows for exceptionally fast boost venting in a compact and lightweight package. Materials have been selected to minimize the inertia of moving parts allowing it to respond faster than competitor's products. Piston shape and exhaust port design ensure that air can evacuate as quickly as possible. Hard anodizing and teflon coating of the piston minimizes sliding friction while providing for long term wear resistance. Direct replacement of the factory valve. Supplied with elbow for connection to recirculation hose.

Usually ships in 1 to 2 days.

Manufacturer: Cobb


  • Subaru WRX STI MY15+
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How does the bypass or blow off valve operate? If the throttle plate is closed suddenly during positive pressure conditions, the spinning compressor wheel will continue to build pressure between the turbo and the closed throttle. If this pressure is not relieved it can result in a damaging condition called compressor surge. This condition rapidly slows or stalls the compressor wheel introducing significant turbo lag should the throttle be quickly opened again. Additionally, the turbo's bearings and shaft components will be subject to severe loading resulting in accelerated wear or damage. The bypass or blow off valve dumps this pressure before surge can occur. The valve is connected to manifold pressure and operates when the pressure differential before and after the throttle plate is large enough to overcome the spring pressure holding the valve's piston closed.

What is the difference between a bypass valve and a blow off valve? A bypass valve recirculates the air flow back into the intake sysetm (between mass air flow (MAF) sensor and the turbo inlet. A blow off valve (BOV) dumps the air flow to atmosphere.

Can this bypass valve be used as a blow off valve to dump to atmosphere? Yes, if the recirculation hose is removed and the connection to the turbo inlet hose plugged off this valve can be used as a blow off valve. However, it is only recommended when running a speed density setup. With MAF-based tuning this will cause a momentary rich condition every time the valve opens (because the fuel calculations are based on air flows that never make it into the engine).

What is the purpose of the adjustment on the valve? The spring preload is adjustable in order to fine tune the pressure differential required to open the valve. Basically how "hard" or "soft" the valve blows off.