My son added a Boost gauge to his 1999 S70 T5 5Sp. He has “T”ed it off the vacuum line that is on the Intake manifold.Is this a Good-Bad or “SO-SO” placement?WHEN Not Driving… it shows around 20-25 on the vacuum side.When Getting on the Gas driving, it shows around 10 PSI of boost.

Are these accurate based on Placement of “T”ed lines?

 

The only accurate placement of the boost gauge will be on the pressure side of the turbo. If you T into existing lines, you will be messing with a vacuum signal that is already there for vacuum, not pressure.

 

Tony is totally wrong - people with boost gauges (like me) want to see manifold pressure. So that part your son did well. Your measurements are good, same as my car.


The gauge doesn't interfere with flow or pressure on any other system, but flow (like in a purge line) by definition has to affect pressure at the point where the gauge is teed in. It would be totally best to run a separate line right to the tree, but the difference might not even be measureable. I say "good enough".