GrimmSpeed V2 Bypass Valve – Red | 2004–2021 Subaru STI | EJ257 | GRM126032RED

STI (EJ257) only — not for the WRX (EJ255 or FA20DIT). Confirm your vehicle is the STI before ordering.

Recirculating design — not a vent-to-atmosphere BOV. Maintains factory recirculating function with no BOV sound and no MAF-related idle issues.

GrimmSpeed GRM126032RED V2 bypass valve for the 2004–2021 Subaru STI with the EJ257 engine. Red anodized billet aluminium body. Direct OEM replacement fitment. 1.5 lbs. Ships fast across Canada and the US.

Why Replace the Factory STI Bypass Valve

The EJ257 STI uses an internal bypass valve (BPV) that recirculates compressed air from the compressor outlet back to the compressor inlet on throttle lift. The factory valve uses a plastic body and rubber diaphragm that are adequate at stock boost levels but become a common failure point on modified or tuned STIs running elevated boost. A cracked valve body or failed diaphragm allows pressurised air to escape at the bypass valve rather than being contained in the intake tract — causing boost leaks, inconsistent boost buildup, and a loss of power that can be difficult to diagnose without a boost leak test. GrimmSpeed’s V2 replaces the factory plastic and rubber construction with a machined aluminium body and a more durable diaphragm rated for sustained higher boost operation.

GrimmSpeed V2 — Improved Over V1

The V2 is GrimmSpeed’s second-generation bypass valve design, updated from the original with improved diaphragm material and sealing geometry for more reliable long-term operation under elevated boost. The V2 uses the same direct OEM replacement mounting as the original — bolt-on installation with no modifications required to the factory intake piping or intercooler connections.

Recirculating — Not VTA

The GrimmSpeed V2 is a recirculating bypass valve — it routes excess compressor pressure back to the intake pre-compressor, exactly as the factory valve does. It does not vent to atmosphere. This means no BOV sound on throttle lift, no mass airflow sensor complications from venting metered air, and no rich stumble at idle after lift events. The recirculating design is the correct choice for street-driven and E-tuned STIs where drivability and MAF accuracy are priorities. Buyers seeking an audible vent-to-atmosphere setup should look at GrimmSpeed’s or other manufacturers’ VTA BOV options instead.

Red Anodized Finish

The GRM126032RED features a red anodized aluminium body — a popular colour choice in the STI engine bay. GrimmSpeed offers the V2 BPV in multiple anodized colours; all are functionally identical. Select the colour that complements your engine bay build.

Fitment

• 2004–2021 Subaru STI — EJ257 engine
• GD/GG (2004–2007), GR/GH (2008–2014), VA (2015–2021)
• STI only — does not fit WRX (EJ255 or FA20DIT)

STI EJ257 only — not for WRX. Recirculating design — not VTA. Direct bolt-on OEM replacement. Inspect intercooler pipe connections and clamps while the bypass valve is removed. Re-check for boost leaks after installation with a boost leak tester before returning to full boost operation.

Specifications

• Brand: GrimmSpeed
• Part Number: GRM126032RED
• Model: V2 Bypass Valve
• Finish: Red anodized aluminium
• Type: Recirculating bypass valve
• Engine: EJ257 (STI only)
• Weight: 1.5 lbs
• Application: 2004–2021 Subaru STI