Disadvantages of BOV

The advantage of a BOV or a  blow off valve is that it prevents a phenomenon known as a compressor surge. Compressor surge kicks in when the throttle of an unvented turbocharged engine closes. By closing the throttle plate of the turbo engine, the throttle traps the pressure (which is of quite a high scale) in the intake system and forces the pressure wave back to the compressor. This occurrence slows down the compressor wheels, even bringing it to a complete halt. It finally creates a hissing or fluttering sound that is easily heard by the driver.

Disadvantages of a BOV or  blow off valve

A sensor known as a mass air flow sensor is used to measure the air mass that enters an internal combustion engine. The air mass is significant for the control unit of the engine or the ECU (Engine Control Unit) so that the correct mass of fuel can be balanced or delivered to the engine. But when a mass airflow engine is used on the  blow off valve or BOV, the engine control unit displays more fuel than is actually used. This is because it doesn't take away the measurement of the intake charge. The engine then starts working for a brief period on a fuel-rich mixture.

This fuel-rich mixture can stall or thwart the movement of the engine. It happens when the throttle is closed. The situation is made worse with boost pressure of higher magnitude. Random or occasional events as such can only be a headache, but frequent events of this type can negatively influence the catalytic converter and the spark plugs.