1 Bar = 0 vac = Atmospheric
2 Bar = 14.7 psi
3 Bar = 29.4 psi
4 Bar = 44.1 psi

 

that's true in relation to turbo's, but what i posted earlier is the scientic result of 1 bar, etc. 1 bar is not a vacuum, it is 1.01325 atm which is approx. 14.7psi as per General Chemistry, Petrucci, 1999

I understand when relating to turbo's that 14.7psi is a "boost" factor and the original 1 bar/atm that is found at STP (standard temp/pressure) is not included but it still occurs in the cylinders. Since all cars run under 1 bar/atm at 14.7psi, it's stupid to mention it everytime.