I live in Colorado @ approx. 9,600' above sea level and have an 88' 22RE that I just rebuilt. I wanted to know what an ideal compression reading would be.
It seems the reading at sea level would be higher.

I had 125-128 in all 4 cylinders before the break-in procedure, and have not retested yet.

 

I found the info here after a day of googleing if anyone wants it:

Altitude Factor
500 0.987
1500 0.960
2500 0.933
3500 0.907
4500 0.880
5500 0.853
6500 0.826
7500 0.800
8500 0.773

So my 125 @ n9,600' should be about 165 at sea level.

 

shouldnt an engine compress the same amount no mattter what?

 

Yes, it will just take longer to do so because of thinner air.

 

The compression test on a new engine at high altitude should compensate for the air that is less dense. Thats what my mechanic (35 years exp.) saysas well. Up here there is literally less air to compress in a given space. So the above formulas are correct. So if I get 125 @ 9,400', then I would get around 165 at sea level.

 

no the air is less dense, less given gas per volume of space, or the air is thinner. if you filled your lungs with air on pikes peak and blew up a baloon it would be smaller than a baloon at sea level. at less atmospheric pressure the air at sea level would be comparable to running a turbo with two pounds of boost here to make up the pressure difference. thats why naturally aspirated diesel dont like high altitude not enough air and they smoke like crazy from the excess fuel at sea level thay would be just fine. sorry if this is confusing but ive had a few beers so bear with me

 

i guess it would compress the same volume but that is a moot point since it is the density change that is effected