So, this may be a stupid question, and I did a search and didn't come up with anything that really helped. My boost controller measures in BAR, and I know the conversion for that to PSI, however, it measures vacuum in cmHg, well I assume its vacuum(the lower half of the guage, the value the needle is on when not boosting). I'm just curious as to what the cmHg value represents. I googled it, and I'm not going to lie that just confused me more.

 

The vacuum reading is not represented in PSI on any gauge.

 

I understand, but what is the cmHg measurement?

 

im not sure of the cm maybe it means centimeter but hg is the measurment of mercury so i think since your guage is metric it should be centimeter of mercury because in automotive repair 20''hg means 20 inches of mercury,which is the intake manifold vaccum reading of a healty motor.

 

cmHg = centimeters of mercury

Divide by 2.54 to get inHg ("inches of mercury"), which is more common on U.S. boost/vacuum gauges.

So, if your gauge reads 40 cmHg, that would be 40 / 2.54 = 15.7 inHg.

-Max

 

Thanks, thats what I was looking for.