Boost Gauge Question

[Brad Bell]

Hey everyone, i just have a quick question. How exactly are you supposed to read boost gauges. The one in my car (which I bought off a guy) has one with the vacuum side and the boost side type. I uploaded a photo to show you what I mean. Personally I think the gauge in my car is not setup right, when i rev the car the needle in the gauge gets even more vacuum, or its not even going toward the boost side. It stays in vacuum all the time. It's a mechanical gauge and its tapped into the intake manifold. Not sure if i'm just reading it wrong or if there's actually a problem. Thanks!

 

[pauleyman]

A light free rev wont build boost. What does it do when you drive it and hammer it?

 

[luv2rallye]

^+1. Boost only shows up (in intake manifold) when engine is under accelerating LOAD with a working turbo (ie. accelerating in gear with wheels on ground, in other words - hammering it while driving). Otherwise intake manifold has vacuum (due to vacuum created when pistons go down) since the turbo is not boosting (ie. not creating positive pressure). All mechanical boost gauges have half vacuum and half boost on the dial to indicate the pressure in the intake manifold.