Trying to test my valves while i'm replacing my plenum. I noticed the venturi tube when putting pressure from the plenum side seems to allow air to the tube that connects to the Y-pipe? Is this normal?

 

Did a little more research and I think this is normal. In case someone is wondering I learned alot from understanding venturi tubes and suction jet valves from Audis/VW (I think this is the same part honestly).




There is a check valve between the plenum connector and the brake booster so that flow is only in the red arrow.

There is no check valve between the y-pipe and the plenum because when you are under boost there is no pressure differential (should be the same so that wouldnt cause any issues.

When the throttle is closed, the vacuum in the plenum is sucking air from the Y-pipe through a small opening and accelerating the vacuum from the brake booster thereby making your brake pedal feeling better. At least this is how I understand it.

 

TY for sharing