This mechanical exhaust flap (for subsequent assembly) regulates the total volume of your exhaust system by negative pressure. This exhaust gas flap is closed in the unpressurized and uncontrolled state. This exhaust gas flap is open at idle and at low speed and a sporty / loud exhaust sound sounds. The position of the exhaust flap on naturally aspirated engines is determined by the negative pressure that exists in the intake manifold. With turbocharged engines (turbo, compressor), the negative pressure only forms when starting, while driving (without boost pressure) or when idling/shifting. It is advisable to also install a vacuum tank. When the speed increases, this flap closes and the exhaust system becomes much quieter. So even with strong acceleration, the sound of your vehicle remain.
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