Manifold absolute pressure is in PSI, however I want to know how this relates to engine vacuum. Does the map sensor read a pressure change from the standard pressure?

 

"Manifold absolute pressure sensor - Monitors the pressure of the air in the intake manifold
The amount of air being drawn into the engine is a good indication of how much power it is producing; and the more air that goes into the engine, the lower the manifold pressure, so this reading is used to gauge how much power is being produced. "

howstuffworks.com

 

So can it relate to vacuum?? I saw a web page once that equated the map sensor voltage to vacuum. Who knows if that was accurate or not.