The anti-surge valve increases the boost and is used in Roots superchargers.

• A. True
• B. False
• C. Not used
• D. Only on turbochargers

Answer: (B)

An anti-surge valve is there to prevent compressor surge by relieving excess pressure when the air flow through the compressor can’t keep up with the boost. In Roots superchargers, if the rotor speed creates high pressure but the engine can’t draw enough air at that moment (such as at low RPM or sudden throttle changes), the valve opens to bypass or vent some of the compressed air. This stabilization protects the compressor and smooths operation, not by boosting the output, but by preventing instability.

Because of that, the valve does not increase boost; it often reduces effective boost when it opens. It is indeed used with Roots superchargers to prevent surge, and it isn’t limited only to turbochargers.