That’s what I thought too … but spoke with a flight engineer AME last night and he says a 9” venture is minimum to run my 2 gauges AH and DG.

He says the high reading is due to the location of the suction gauge in relationship to the venturi and instruments … closest to venturi will give highest reading.

I need to take a good look at the plumbing to check/move location of the suction gauge.

Jeff

 

 

Sounds like you really just need a smaller venturi.  How many vacuum powered gauges are you running?

 

Regulators usually go between the vacuum source and the rest of the system but I can’t recall ever seeing one used in a venturi system, usually only on vacuum pump equipped installations.

 

 

Can anyone explain the following:

I have a 9” venturi on side of fuselage – connected with a 3/8” hose, the suction gauge reads 9”.  This is too much for gyros, so I put a restrictor in the line expecting to get less vacuum – instead it goes to >10”.  This would imply that if hose was larger, vacuum would be less.

If I was to install a regulator should it go between venturi and gauges? or after gauges between them and filter?

I’m getting the feeling that a regulator is actually a “controlled leak” – adjusted by a needle-valve? True or False?

If True, it would make sense to put a controlled leak between venturi and gauges, as any dust would get sucked out of cabin without passing through gauges.

Jeff