Compression pressure

[Carel]

I want to know on a FJ1100 how much the pressure drops from sea level to every 1000m above? I know there is a couple of variables but just as a rough guide!

[Billy Bananahead]

Use your search engine 

[T Legg]

I want to know on a FJ1100 how much the pressure drops from sea level to every 1000m above? I know there is a couple of variables but just as a rough

I want to know on a FJ1100 how much the pressure drops from sea level to every 1000m above? I know there is a couple of variables but just as a rough guide!

the picture has the multiplyers to determine the atmospheric pressure at different altitudes. Its in feet and lbs/square inch .
 I do my engine work at 4786' altitude so I use .8749 for my correction value. One of my cylinders read 136 psi so I divided it by .8749 to determine that it's sea level reading would be about 155.4 psi .
 this isnt exact as like you said there are other factors that can effect it.

[T Legg]

The chart

[Carel]

Thanx, thats what I wanted to know!

[red]

I want to know on a FJ1100 how much the pressure drops from sea level to every 1000m above? I know there is a couple of variables but just as a rough guide!

Carel,

You can get the local barometric pressure from the local weather services. Right now, mine is 30.31 inches (76,98 cm) of mercury.  My house is 4888 feet (1489 m) MSL. For any local altitude, compression of 10:1  will multiply those numbers by ten.  303.1 pounds per square inch equals 1567,48 cm of mercury or 20,89 BAR. 
The actual compression readings will not be as important as all cylinders being equal, or nearly equal.
Here is a handy, capable, and FREE Units Converter app for Windows or Linux (using WINE).  My numbers here come from the PRESSURE tab on that app.
free Units Converter
.

[Firehawk068]

I always use a correction factor for obtaining proper compression readings.
My house is at 5,600 feet elevation, but depending on the season and weather, sometimes "density-altitude" air pressure readings are in the 7,500-8,000 ft range.
I usually go by a weather station that's nearby.