anti-surge compressor cover?

[deezlins]

http://www.sound-performance.com/antisurge.htm

ive never heard of this before? whats the deal with anti-surge and anti-surge deletion?

[IvanAtSPRacing]

When a turbo spools up too quickly, the air has no place to go but spill over the blades of the impeller and this shocks the impeller and slows it down violently. We have seen 10 psi swings during compressor surge. An anti surge housing is machined to have a path for the air to recirculate instead of shock the impeller. Unfortunatly, this causes slower spool and reduces ultimate HP. The compressor cover modifications we do delete the anti surge feature or allow you to tune it.

[WDRacing]

The right sized turbo will not suffer from surge. Usually when you have a huge compressor and a tiny ex housing AR is when you'll get the surge.