GrimmSpeed Bypass Valve RED – 2015-2021 Subaru WRX

The GrimmSpeed Bypass Valve: Engineered Specifically for the FA20DIT VA WRX

The GrimmSpeed Bypass Valve in Red for the 2015-2021 Subaru WRX replaces the factory recirculating bypass valve on the FA20DIT with a unit specifically engineered for the FA20DIT’s boost pressures and MAF-based air management system. The GrimmSpeed valve recirculates compressor-side pressure on throttle-off events, preventing compressor surge without venting metered air to atmosphere — maintaining correct MAF readings and eliminating the lean stumble that a fully atmospheric BOV causes on the FA20DIT platform.

Recirculating Design — Correct for the FA20DIT MAF System

The FA20DIT uses a mass airflow sensor (MAF) to measure the air entering the engine. On throttle-off events, the turbocharger continues to produce boost pressure that has nowhere to go when the throttle closes — without a relief valve, this pressure spikes against the closed throttle and causes compressor surge. The GrimmSpeed bypass valve relieves this pressure by routing it back into the intake ahead of the turbocharger. Because the air is recirculated rather than vented to atmosphere, the MAF does not see a discrepancy between metered and delivered air — no lean stumble, no idle hunting.

Direct OEM Replacement — Bolt-In at Factory Bypass Valve Location

The GrimmSpeed bypass valve installs at the factory bypass valve location on the 2015-2021 WRX FA20DIT using the factory mounting hardware and vacuum reference line. No charge pipe modification, no additional fittings, no re-routing. The Red anodized body provides a clean visual appearance alongside other engine bay hardware. The valve is designed to handle the boost pressures of modified FA20DIT builds beyond factory levels.

Key Features

• Platform: 2015-2021 Subaru WRX FA20DIT
• THIS LISTING: Red anodized finish
• Recirculating design — correct for MAF-based FA20DIT air management
• Prevents compressor surge on throttle-off events
• No lean stumble or idle hunting — air recirculated, not vented
• Direct OEM replacement at factory bypass valve location
• Handles elevated boost pressures of modified FA20DIT builds
• No charge pipe modification required

Fitment Notes

• Platform: 2015-2021 Subaru WRX FA20DIT
• Recirculating only — not an atmospheric BOV
• Direct replacement at factory bypass valve location
• Not compatible with fully atmospheric BOV applications on MAF-based FA20DIT

Straight From Subispeed

The GrimmSpeed bypass valve is the correct recirculating upgrade for FA20DIT WRX builds that want improved boost response and surge protection beyond what the stock valve provides. The Red anodized body is a visual bonus, but the engineering reason to buy it is the improved surge resistance under elevated boost on a modified FA20DIT — the factory valve is adequate at stock pressure but starts to show limitations as boost increases.

What’s Included

• GrimmSpeed Bypass Valve — Red

About GrimmSpeed

GrimmSpeed is a Pacific Northwest-based performance parts manufacturer that has been building Subaru-specific hardware since 2003. Founded by engineers who were actively building and racing Subarus themselves, GrimmSpeed’s catalog reflects the priorities of people who use the products they make — turbo inlets, downpipes, uppipes, boost controllers, intercoolers, and engine bay accessories designed specifically for the EJ and FA-series Subaru platforms. Every GrimmSpeed product is engineered, tested, and refined in-house, and their focus on Subaru means the fitment and function reflect a deep understanding of the specific platforms they cover. Subispeed carries the full GrimmSpeed catalog because their approach to product development consistently produces parts that perform as advertised and fit correctly out of the box.

Year	Make	Model	Notes
2015-2021	Subaru	WRX	FA20DIT MT/CVT