|
The valve is used to alter the sound at particular rpms. Low loads its kept closed to keep the noise down.
On startup the valve is open during cold start, along with the turbo wastegates. This is why the car is loud on first start in the mornings, it is used to heat up the catalytic converters to reduce emissions.
On my car with downpipes there's hardly any difference in sound, just makes the car a little bit more annoying when cruising. Personally I think its a waste of time and if you want better sound you should get an exhaust.
If its rattling you should check if there's a leak somewhere as exhaust flap rattles are sometimes caused by leaks in vacuum lines.
|