What is atmospheric pressure

[Luke Davey]

What is the atmospheric pressure at sea level?

 

[rc331]

I think it is 14.7 p.s.i :confused:

 

[IrishEKU]

rc331 is spot on. ;)

 

[Boozer]

14.7psi or one Bar. i believe it is also called one atmosphere.

 

[DENNY]

14.696 PSIA
760 MM of HG
29.9213 IN of HG
All at 0 Deg. Cel. at sea level and remember this is absolute pressure not gauge pressure.

 

[IrishEKU]

Denny is also correct and wen't further in depth ;) Then of course if you really want to brushup on math and conversion tables you can hit the milibar tables or fool around with the fluctuations in inches of mercury on the scale of inches measured by a barometer. Dependen' on where your local is at ,meaning the mean level at which you are at(Either "Sea Level" on the coast or at what ever your local elevation above or below that you are at. Next you will also have to check your local weather while testing. A drop below 30.00 inches means that LOW pressure is bulding leading to a storm or a slight depression in air density in the area. I really don't know if this will really affect your results, maybe one of the mods can shed a little mor light on it for you :cool:

 

[Jaybird]

Luke,
I know you posted asking about the atmospheric pressure the other day concerning the compression test of your engine. I mentioned it would not make a difference on your guage and I guess you don't believe me. But I feel very confident when I repeat that the atmospheric pressure changes that we see will not effect the compression test of an engine combustion chamber.
Just what formula would you use for this test if you were to KNOW what your pressure was at any given time?

 

[DENNY]

Did I miss something? Compression is measured in gauge pressure and the atmospheric pressure is compensated on a quality gauge with a zero adjustment. When measuring compression the variations in atmospheric pressure are negligible.

 

[Luke Davey]

I believe you Jaybird, but one of my questions in my original thread was what is the atmospheric pressure, no one answerd it. So i posted this thread hoping to find out what the pressure really is. I do not mean to offend you in any way. So know i know it is 14.7 psi, thanks to all

 

[Jaybird]

You didn't offend me in the least, Luke. I simply wondered if you planned on adding or taking away for atmospheric pressure to read your guage, which would be a mistake.
I'm no physisisisist at any stretch, but I think that doing a test of this nature in a closed environment blows atmospheric pressure out of the equasion.

 

[Luke Davey]

Thankyou everyone, im going to pull the head and cylinder off and measure everything .

 

[DENNY]

Now I understand the question. Gauge pressure, used by common pressure gauges is referenced from the atmospheric pressure of the day being zero PSI. Atmospheric pressure or absolute pressure scales are used in barometers and referenced to an absolute vacuum, zero PSIA. In general pressure measurment the variance in atmospheric pressure is negligible but this small pressure change does have effect in altitude, temperature, and density of the air. The difference is 4.5 PSI from sea level to 10000 feet. This is why quality pressure gauges in PSI have a zero adjust.