The factory gauge is in "mmHg" (Millimeters of Mercury).
1 psi = 51.71 mmHg (0.06 bar)
7 psi = 362 mmHg (0.48 bar)
12 psi = 620.52 mmHg (0.72 bar)
14.5psi = 1,023 mmHg (1.00 bar)
The factory boost gauge is rated to "7" (x100 mmHg) = 700mmHg
So that means:
7psi (factory boost) = 362 mmHg (about 50% up the gauge).
12psi (limit of factory turbo) = 620 mmHg (about 95% up the gauge).
14.5psi (1 bar) = flat lining on the "7+" (time to get a better boost gauge).
Their we go, learnt something myself.
Reference: Page 2 of http://content.honeywell.com/sensing/prodi...cal/c15_125.pdf