The Turbosmart BOV controller is an electronic device that controls the pressure signal to the BOV. It works by detecting a negative voltage change in the throttle position. It then energises a solenoid to vent all of the air out of the BOV cap, causing a pressure differential between the piston of the BOV and the cap, which will vent pressure from the intake system. Diesel engines can experience compressor surge when coming off the throttle. The engine's deceleration can restrict the outlet of the turbocharger, causing a compressor surge. This can be disastrous on a turbo system producing high amounts of boost. The BOV controller can vent this build-up of pressure, protecting the turbocharger. This can reduce the number of rebuilds on your turbocharger as well as improve acceleration between gears.