With power to the Automoter boost gauge, but the engine off the boost gauge reads "0". With the engine at idling the gauge reads ~10.5 lbs of vacuum. So why doesn't the gauge read lower than "0" at this elevation? Either the gauge is not that accurate, it self-calibrates or??

Today at the autox I saw a max oil temp of 231 degrees and a low oil pressure at idle, at that temp, of 12psi.

 

You have now seen the difference between "gauge (psig/mmhgg)" pressure and "absolute (psia/mmhga)" pressure. Absolute pressure is exactly that; pressure referenced from zero. Gauge pressure is referenced to atmospheric, i.e 0 psig at sea level is in reality +14.7 psia. As your elevation rises, the absolute pressure drops, but the gauge will continue to read 0 psig with no vacuum/pressure applied. This is fine in the case of automotive gauges, which have always read 'gauge' pressure. Gauges and instruments are available which measure absolute pressure (a barometer is but one example), and the method used by the fuel injection system in cars uses absolute pressure as well.

If your everyday automotive gauges were to read absolute pressure, you would have to contend with 'zero shifts' and confusing offsets.

Dont worry about the gauges not reading absolute, since your car (and everything else for that matter) work by referencing atmospheric pressure. If you want absolute, simply add the barometeric pressure of your location for a correction factor.
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"Earl Grey" - '03 MCS, DS over DS, 17" R85s, NAV, DSC (often turned off!), Packs #1 and #3, Rally lights, etc, etc. Perf Mods by the boatload, on the way! Fulton, MD. FRS 7-21
Let's Get Small!

 

CM,

Didja ever finish your install FAQ?

 

No, moved onto other projects. But if you need help send me a PM and I'll see if I remember anything.
Mark