Blow-off control
Like the N63 engine, the N74 has electric diverter (blow-off) valves incorporated directly into the turbochargers.
The blow-off valves reduce unwanted peaks in the charge air pressure that can arise when the throttle valve is closed quickly. In doing so, they perform an important function with regard to engine acoustics and contribute to protecting the components of the turbochargers.
Diverter (Blow-off) Valve
If the throttle valve is closed, the charging pressure (before the throttle valve) and its rise are compared with stored nominal values. If the actual values are a certain value above the nominal values, the blowoff valves are opened. This diverts the boost pressure to the intake side of the compressor and eliminates the unwanted pressure that can damage system components.