Why Turbocharged vehicles need atu run a bypass/blow-off valve (CBV/BOV)?
The turbocharger is moving large amounts of air while under boost, and this pressure is being delivered to the engine while the throttle is depressed. As soon as the throttle is lifted the butterfly closes in the throttle body preventing the pressurized air from entering the intake manifold. That dense charge air now has nowhere to go. Because the engine is still moving exhaust gases and the inertia of the turbocharger is turning the turbine and compressor wheels, the air literally stacks up against the throttle blades. Pressure builds up within the system’s piping extremely quickly and once it reaches the compressor wheel the air actually flows back out of the compressor inlet and limits the compressor from rotating. Because of the air reversing direction the pressure drops allowing the wheel to spin and once again raise the pressure. This process of up and down pressure and air reversal is surge and the result is the fluttering/barking sound that comes from the turbo. Surge is very d
