The stock turbo has an integrated "electric" diverter valve, which expels boost on throttle lift.
Upgrading to a Garrett GT/GTX turbo eliminates the stock “electric” diverter valve through replacement of the stock turbo. The stock “electric” diverter valve offers limited flow potential and inadequate for increased airflow from an upgrade performance turbo.
Replacement of stock “electric” diverter valve is necessary; and requires a high flowing “mechanical” or vacuum actuated valve to handle increased flow on throttle lift from an upgrade performance turbo.
Recommend TiAL Q Blow Off Valve (ATP product code: TIL-BOV-007, TiAL Q Blow Off Valve) for best overall performance and reliability. The TiAL Q Blow Off Valve with 1" hose clamp style mounting flange, plugs to the 1" port provided with each ATP Fiesta ST GT/GTX turbo upgrade. Additional requirements to run an actuator hose to blow off valve:
1) Vacuum fitting adapter (ATP product code: ATP-FIE-005, Vacuum Source Block for 2014+ Fiesta ST)
2) 6 feet of vacuum hose (ATP product code: ATP-SIL-246, 3/16” (4.7mm) inner diameter extruded silicone vacuum hose)
Note, the Fiesta ST runs perfectly with a vent to atmosphere BOV and will not cause drivability issues. Although we recommend a TiAL Q Blow Off Valve for overall durability, you can use ANY brand of valve you choose and trust.
In order to prevent fault code you may disconnect the stock “electric” diverter valve from your ECU tune. If your ECU tune cannot disable the stock “electric” diverter valve, you may leave the electrical circuit plugged in to prevent a fault code. “Sim- Plug” may also simulate the electrical draw of an active stock “electric” diverter valve.