(to make Wes happy)

Wastegate bleeds off exhaust pressure to reduce the pulses/pressure that the exhaust turbine of the turbo receives. The desired side effect is controlling the amount of boost produced by the intake side of the turbo.

A blow off valve eliminates compressor surge. Once the throttle body closes (when you lift off the throttle) there is a surge of pressure on the side of the throttle body that the turbo is on (opposite the motor.) This surge of pressure backs up and then must force it's way out somewhere. The BOV will relieve the pressure. If the pressure is not relieved by the blow off valve, compressor surge happens, which means that the air is forced out the turbo. This makes a funny "ch-ch-ch-ch" noise, and can apparently cause damage in high boost applications....

Chris

 

LMAO...I love this and hope it catches on, instead of replying to the numerous ignorant posts. Think how much time and bandwith this could save.