Tried every way and can’t get it proper working way, making boost bar from -1 to +1.5, made 2 bar gauges, positive part 0 to +1.5 is easy, but -1 to 0 is impossible. want to work it from the right to left and it seems to work with bug because on the left side should be -1 not 0… I think its a bug or maybe we could choose some kind of “invert” mode? tried to do some gauge math, but boost has no ID
If you use boost, see how this is implemented in the developer panels. It is well shown there.
For me it seems to work ok like this:
- Create new Bar Gauge
- Link it to Calculated Values->Boost (Bar/Psi) and set range and levels to your liking
- Go to Look’n Feel
- Go to Special->Style and select ‘Right to Left’
- [optional] Go to Autoscaling and enable it to draw numbers and/or segments.
there’s a trick, I found out that you need to have text gauge covering whole range (then make it invisible in the project by setting opacity of the text to 0) in my example -1 to +1.5 to handle negative range on the bar gauge with crazy setting of 0 at min field and -1 at max 
and its working, of course you have to set it “right to left”