GFB HYBRID TMS Dual Port 35mm Inlet/30mm Outlet 97-98 Subaru WRX/STi

GFB's Original Dual Port Design Returns for the 1997-1998 Subaru WRX and STi with Full Vent, Full Recirc, or 50/50 Configuration

The GFB T9235 Hybrid TMS is a direct factory replacement blow-off valve for the 1997-1998 Subaru WRX and STi, designed as a drop-in unit that bolts to the same location as the OEM diverter valve without modification. GFB pioneered the dual port blow-off design with the original Hybrid in 1999, and the GFBT9235 carries that technology forward with a configurable outlet system that lets you choose full recirculation for a quiet and stock-like operation, full atmosphere vent for maximum blow-off sound, or a 50/50 split for a middle ground. The staged venting design opens the recirc port first at low valve lift, then progressively exposes the atmosphere port as boost pressure rises, giving a proportional and tunable response that protects the MAF sensor circuit on factory-tuned applications.

Key Features

• Direct factory replacement for the OEM blow-off valve on 1997-1998 Subaru WRX and STi; no modifications required
• Dual port staged venting: recirc port opens first at low lift, atmosphere port opens progressively at higher lift
• Configurable for full recirculation, full atmosphere venting, or 50/50 venting using included blanking plugs
• 35mm inlet (fits 32-35mm ID hose or 25.4mm OD metal pipe); 30mm recirculation outlet
• Adjustable spring preload screw for tuning valve opening sensitivity to match boost level and driver preference
• TMS (Turbo Management System) technology ensures rapid boost recovery after a gear change
• Rated to hold boost pressures exceeding 100 psi; suitable for modified high-boost applications
• Includes blanking plugs for full recirc or full atmosphere configuration

Vehicle Fitment

Specifications

What's Included

• 1x GFB T9235 Hybrid TMS dual port blow-off valve
• Recirculation outlet hose plug (for full atmosphere configuration)
• Atmosphere port blanking plug (for full recirc configuration)
• Grub screws with lock nuts for pipe mounting
• 5mm hex key for spring preload adjustment

About Go Fast Bits

Go Fast Bits (GFB) is an Australian performance engineering company that invented the dual port blow-off valve design in 1999 with the original Hybrid. Since then, GFB has been a leading manufacturer of blow-off valves and diverter valves for turbocharged vehicles worldwide. Every GFB valve is engineered to solve real-world issues with factory valves on modified and stock turbo cars, and is rated to withstand boost pressures beyond what any street or track turbo application can produce.

Frequently Asked Questions

The GFB T9235 is a Hybrid TMS dual port blow-off valve designed as a direct factory replacement for the 1997-1998 Subaru WRX and STi. It uses a staged dual-outlet design that vents to recirculation first and progressively exposes the atmosphere outlet as boost pressure rises, providing a configurable sound profile from silent full recirc to full atmosphere venting.

Yes. The T9235 is designed as a direct factory replacement for the OEM blow-off valve on the 1997-1998 Subaru WRX and STi. It mounts in the same location using the factory hose connections with no cutting, welding, or fabrication required.

To run full atmosphere venting, disconnect the recirculation hose and block it with the supplied hose plug. Install the screw-in plug in place of the recirculation outlet on the valve body. This routes 100 percent of the vented air to the atmosphere outlet for maximum blow-off sound.

To run full silent recirculation, keep the recirculation hose connected to the recirc outlet and swap the atmosphere trumpet for the threaded blanking plug. All vented air is returned to the intake tract upstream of the turbo, resulting in a quiet, stock-like operation with no atmospheric venting.

The dual port design minimizes stalling risk by staging the atmosphere vent to open proportionally rather than all at once. When set to full recirculation or 50/50, the T9235 is safe for MAF-equipped applications. For full atmosphere configuration, adjust the spring preload to the appropriate setting per the included instructions to prevent idle drop after a hard gear change.

The T9235 also fits the Nissan 300ZX Z32 (two valves required), Nissan Silvia/200SX S13 with SR20DET engine, and Nissan Pulsar GTi-R N14 (requires a softer spring, GFB part 6116, sold separately). For custom installations on other vehicles, the T9235 can be used with a 32-35mm ID hose or welded onto a 25.4mm OD pipe.

Use the supplied 5mm hex key to turn the preload adjustment screw. Turn toward the plus sign to increase spring tension, which raises the boost pressure required to open the valve. Turn toward the minus sign to decrease tension. GFB recommends starting at the softest setting and firming up by one turn at a time until the engine returns smoothly to idle after a hard throttle lift-off.

Periodic cleaning is recommended. Remove the four cap screws to access the piston, then wipe the piston and bore with a clean rag and apply a light coat of engine oil to the piston and the inside of the bore before reassembling. No other scheduled maintenance is required under normal operating conditions.

Installation Instructions

1. Remove the factory OEM blow-off valve from the turbo piping on the 1997-1998 Subaru WRX or STi.
2. Connect the T9235 base to the factory inlet hose and secure with a hose clamp seated on the straight section of the fitting, not on the retaining bead.
3. Connect the recirculation outlet to the factory recirc hose with a hose clamp.
4. Connect the 4mm vacuum line to the T9235 vacuum nipple. Run the line to a manifold vacuum source located after the throttle body. Keep the line as short as possible.
5. Do not connect the vacuum line to boost control, fuel pressure regulator, or brake booster lines.
6. Set the spring preload adjustment screw to the softest position (3mm above the head of the valve cap).
7. Start the engine and let it idle for two minutes with the A/C off. Confirm the piston is fully closed at idle. If the piston is hovering open, tighten the spring in the plus direction until it closes.
8. Stab the throttle and release quickly. The piston should lift and vent, then close smoothly. If the engine stumbles, tighten the spring one turn at a time until idle recovery is smooth.
9. Take the car for a drive. If the revs dip below idle when stopping quickly from boost, tighten the spring 1-2 turns. If fluttering occurs at low RPM, loosen the spring one turn at a time.
10. Configure atmosphere/recirc plugs for desired sound level per the included instruction sheet.