A blowoff valve (BOV), dump valve or compressor bypass valve is a pressure release system present in most modern OEM road car applications. Its purpose is to prevent compressor surge / stalling and reduce wear on the turbocharger. These control valves remove the damaging impact of ‘surge loading’ by allowing the compressed air to vent  away from the compressor wheel. This discharge can be heard as a distinct ‘dump valve’ hissing sound as it vents to atmosphere or back into the intake depending on the application and ECU airflow regulation. The Fiesta ST 1.6T Ecoboost uses an inexpensive electronic diverter valve as standard which is prone to failure and inconsistent results when used at higher boost pressure.

Plumb Back Kompact Shortie Kit for Ford Fiesta ST 1.6T
Stock blow-off valves like those that come standard with the Fiesta ST often suffer from a range of problems. They are plastic, and they leak, and if you want to up the power (who doesn't?) they have trouble holding the extra boost. You’ll have no such troubles with Turbosmart’s Kompact Shortie blow-off valve. ​Like all Turbosmart blow-off valves, the new Fiesta ST Kompact Shorties have been designed, machined and hand assembled in-house. Keeping the process in-house, ensures only the best quality, and the aircraft grade aluminum alloy construction means cracking and leaking even under increased boost levels will never be an issue. The Fiesta ST Shortie is produced with a light-weight, brass/aluminium, two-piece piston, which is then perfectly matched with precision engineered springs, giving razor sharp valve response, and a serious increase in performance over stock valves.