Anyone knw where this vacuum is going on the car and can anyone explain to me the function of the venturi tube that we find on top of the engine?

thanks

 

If its the one I'm thinking of it is the brake booster.

 

yup brake booster..

 

the venturi actually makes vacuum. hose #12 is on the wye pipe hose 11 goes to the plenum. they bypass the T/B. so when you let off the gas that line now provides some of the idle air almost like a stepper motor but not really as it is a constant volume and the t/b can add more if needed. I may be removing this from my car and will tell you how I make out. if you take the #9 and blow compressed air through #12's port, port for #6 will be under vacuum, if you try to blow air from #11's port you can not as it has a check valve in it.

 

wow, happy i asked, i never would have guessed. Thanks for you explanation Tim, very appreciated, now i understand how that thing works.

 

Just an FYI, my venturi tube #9 failed a few years ago, and caused an amazing number of codes. It was leaking around the large ring cap that attaches to #6. Pressure test with soap and water caught it.

Tom