I don't have a vacuum pump on my Duke's Pressure Outlet Valve.  I do not believe it is needed.  The device might function better (although I can't prove that), but it is not necessary.  I recall that it is to help the valve move initially (and has no value after that first movement) and effect a seal early in the pressurization process.  But incoming cabin air commands it to move when throttle pushes incoming air above ambient pressure.

And I agree that the squat switch from gear is not needed, due to the prompt neutral pressure event when MAP drops below ambient and cabin pressure back flows into the upper deck.

Also, the Cabin Dump switch on the panel is useless.  This switch commands the Duke's Valve to open fully.  If you want to dump cabin air, you throw the door seal switch.  You can also pull the cable that controls the mixing box (firewall) that blocks incoming air into the cabin.  Don't give a useless switch any real estate on your panel.

My thoughts.

Jeff L
LIVP




Hello Dico,
You will need a vacuum port to the Dukes pressure valve for the pressurization to work correctly, I do not have any gyro instruments either but I needed to install an electric vacuum pump near the Dukes valve
Kamal T
N1104T