This document discusses blow off valves which help prevent compressor surge in turbocharged engines and reduce wear. A recirculating blow off valve recirculates boost pressure back into the intake before the turbo to help maintain turbine speeds during shifts, while a vented blow off valve simply releases boost pressure to the air and has simpler components.

2.  prevent compressor surge
 reduce wear on the turbocharger and engine
 help maintain turbine speeds in-between shifts

3.  Recircurlating blow off valve
o A must for car that use Mass Air Fuel (MAF)
sensor
o The boost pressure is recirculated back into
the intake just before the turbo.

4.  Vented blow off valve
o The boost pressure just released to the air
o Have simpler component

5. Throttle
plate
Blow off
valve
Turbocharger
compressor
POSITION