ARMA Variable Exhaust Valve (VEV)
This is definitely an interesting and ultimate tuning of exhaust system.
ARMA VEV has three modes which are respectively fully-opened, fully-closed, and AUTO mode.
1. When the valve is on fully-opened mode, it means you can get a free flow exhaust, and it will sound a throaty growl. The car won’t lose power at high rpm.
2. When the valve is on fully-closed mode, it helps the car get exhaust backpressure and increase torque at low rpm.
3. When the valve is switched to AUTO mode, it will open and close by car owner’s self-setting according to individual driving custom. At this mode, you can set the VEV open and close by detecting various signals, such as boost, depth of gas pedal, rpm.
Two specs of ARMA VEV: 76mm (3 inch) and 60mm.
Also, you can link to the following webpage to get more information about ARMA VEV：
ARMA - BMW Supercharger