Blow off valve - should it be closed at idle?

[LegoHead]

Been reading a few articles and it looks like the blow off valve should be closed at idle or cruise conditions, but mine is always open at idle....

Can anyone confirm if it should be closed?

 

[mx1_champ]

i thort they should be closed on idle . does it close up on boost ?

 

[LegoHead]

Will check if it closes on boost. Also read that if the turbo produces boost at idle and air is leaving the BOV instead of being sucked in then it could be normal.

 

[BenR]

Its normal on some cars.

Mostly depends on the amount of air the turbo can process at idle vs the consumption requirement of an idling engine (very small) and the spring pressure in the valve.

If you touch the throttle it should close immediately, not due to boost, but due to reduced manifold vacuum.