Can anyone tell me why the boost gauge reads i minus figure when off boost?? I thought it would just read 0???

 

they just do lol
You'll always get a negative boost before the turbo spools up...

 

When you're off boost the engine is sucking air (minus reading as it's a vacuum), when you're on boost air is being forced in so a positive reading is given.

 

Ah,that makes sense now. Thanks for that.

 

No prob.

 

mike's summed it up perfectly and simply.

The OP might be interested to know that you can buy boost gauges that are calibrated from 0bar/psi, so only register from that point on i.e. only positve boost shown - when turbo's blowing...