Rick wrote in message link.net...
Steven Shelikoff wrote:


It would probably be better for you to define an absolute vacuum as 0
psi instead of -14.7 psig.

It is far better to describe it as it really is. An absolute vacuum (or
as close as we can get to one) is about .0049 psi.

There is no such thing as -X.X pounds per square inch.

All depends on the reference. If you are measuring with a gauge where
"zero" is atmospheric pressure then you would see it go below zero
PSIg when suction (vacuum) is applied. If your reference is actually
zero, then yes, there is nothing below zero PSIa.

But then again we are talking about the vacuum (or low pressure) in
the intake of an engine. Intake pressure is normally measured in
inches (Hg) --- perhaps to avoid this arguement altogether.