I did a compression test this past weekend. My numbers cam up in between 141 and 145 accross the board. I live at approx 6000' above sea level. Is there some sort of correction for high altitude compression readings? I did a search and have found one qoute saying so. I just want to confirm that Im not on the low end of the reccomended values.

thx
cb

 

bump

 

I don't know of a correction, but mine were about the same here in Colorado Springs @ 6000'.

 

Don't worry too much. My compression came back 131/131/130/130 last year at a similar altitude. I don't burn oil and make power that is directly comparable to other cars up here with similar mods. If you are concerned you could always do a leak down.

 

+1

 

Treating it as an ideal gas, you can just do an absoulte pressure correction on it.

measured compression pressure * 14.7/ / ambient pressure ~= corrected compression pressure


I would expect your local ambient pressure to be ~11.5-12 PSIA
140s seems normal for the altitude.

As usual, pay attention to how close they values are to each other and don't worry tioo much about their average value. Drop some cams in and you'll really see the numbers drop.

 

Yeah, I have cams and just made sure the numbers were close as opposed to worrying about how high (or low) they all were.

 

Thanks for the help guys. There was only 3-4 psi between the highest and lowest number, so I figured I was ok. But just wanted to make sure..

Thx again.
CB

 

try doing a leak down test if its more then 10 % which is considered awesome, Then i would say that you need to have it cheaked out. but some people are comfortable running more up to 20% I like being in the 5% field though!