Turbo boost/vacuum gauge units

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BobG - 10 Aug 2007 21:03 GMT

I see most boost/vacuum gauges have a split dial and show boost in psi
and vacuum in Inches Hg. I suppose this is just the usual units for
each measurement, but why not have both readings in PSI or Bar or??
Any gauges have this arrangement?

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Don Stauffer in Minnesota - 11 Aug 2007 15:24 GMT

> I see most boost/vacuum gauges have a split dial and show boost in psi
> and vacuum in Inches Hg. I suppose this is just the usual units for
> each measurement, but why not have both readings in PSI or Bar or??
> Any gauges have this arrangement?

Hmmm! Funny. Do you mean the test meters, or original equipment
installed gauges. Many aircraft units were in a single unit, most of
them In. Hg. They read MAP, not gauge pressure. To me that is what
such an instrument should show- a single scale reading zero at 29
inches of vacuum, 29 inches at ambient, and going up from there.
Having never had a supercharged car, I have no experience with such
installations, but don't see why they should be different than
aircraft practice.

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Scott Dorsey - 11 Aug 2007 18:35 GMT

>> I see most boost/vacuum gauges have a split dial and show boost in psi
>> and vacuum in Inches Hg. I suppose this is just the usual units for
[quoted text clipped - 9 lines]
>installations, but don't see why they should be different than
>aircraft practice.

I work in a facility where they measure pressure in barrs, torr, millimeters
of mercury, inches of mercury, inches of water, pascals, pounds per square
inch, pounds per square foot, kilograms per square centimeter, and probably
some other units that I can't think of off the top of my head.

Needless to say, the engineering staff is very good with conversion factors.
--scott

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"C'est un Nagra. C'est suisse, et tres, tres precis."

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