I was checking my defi boost gauge against my AP live boost reading and when the AP was reading -10.9 PSI (manifold pressure I think) the gauge was reading almost 20 (what I thought was PSI). naturally you could see why I was worried, I thought I royally F'ed up installing the gauge. however, I thin realized that the manifold pressure on the gauge is in inHg....what the hell is that short for? TIA

oh yeah, sorry if this is the wrong forum, I wasnt sure exactly what forum it would fall under.

 

Hg is the atomic table name for mercury, a heavy metal once commonly used in thermometers and barometers (but now not used often because it is quite toxic).

Hg is a measurement also called a "Torr," named for an Italian designer of weather instruments. Technically it is how much pressure it takes to move a column of mercury 760 millimeters. However, it is almost idental to the "Bar" which is short for "1,000 millibars".

Thus, 1 Hg or Torr = 1 Bar = 14.7 PSI at sea level.

As a cooincidence, the stock PSI for the STI in 3rd gear is exactly 1 bar, which is why the stock boost gauge is so nice and easy to read. Hg is kind of out of fashion, as measurments go, but it is really the only "metric" version of pressure measurement.

More fun stuff here:

http://www.ilpi.com/msds/ref/pressureunits.html

 

1 Torr = 1 mmHg

inHg is inches of mercury, as opposed to millimeters of mercury, and 1 Torr does NOT equall 1 inHg. Just to clarify since the guy asked what inHg was...


http://dbhs.wvusd.k12.ca.us/webdocs/...nversions.html

Gives all the equations for converting.

 

thanks guys, looks like the gauge is working right then

 

Heh, I thought he typed "inHG" as a typo for "in HG"

 

29.9 inHg=14.7psi=1bar=1kpa=760torr