At 11:01 AM 08/31/2000 -0500, you wrote:
>Is there a calculation which you can use the compression test data to
>calculate the compression ratio on your car?
>
Bill
Theoretically, you can calculate the actual compression ratio by simply
taking a compression test reading with a basic compression tester.
Atmospheric pressure at sea level is about 14.7 lbs/sq inch. This is known
as 'one atmosphere'. If you live in higher altitudes (like Colorado, for
instance) your normal atmospheric pressure might be 0.85 atmospheres or
about 12.5 lbs/sq in. If you life in Colorado and you do a compression test
and it shows a cylinder pressure of 125 lbs, then you have a compression
ratin of 10:1. If you live close to sea level and you have a 10:1
compression ratio then your compression reading would be 147 lbs.
If atmospheric pressure at your location is 13.5 lbs/sq in, and your
compression test reads 115 lbs, then your compression ratio is about 8.5:1
(which is 115 divided by 13.5) I have found this to be a pretty accurate
means of finding your true compression ratio.
If you need to find out what the true atmospheric pressure is at your
location call your local airport weather service. They routinely give that
information to pilots who need to check their gauges.
I'm not a scientist, and my process might not be correct, but it's worked
for me! If I'm wrong, someone please correct me.
Dick Dell
Raleigh NC
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