Compression ratio

["Mike Nakamura" <mike_nakamura@domain.elided>]

We generally speak of compression as a ratio. We all take for granted
the hp generated at altitude is lower, less air in cylinder, less fuel,
less power. Since the exhaust vales open, we'll only generate
proportionate pressure for the altitude. 

So ambient pressure at higher elevations will result in corresponding
lower pressure reading.

Figure battery, rings, etc. all equal.

The Bourdon tube inside the dial gauge is metal and should straighten
out relative to inside pressure. A mechanic should zero the gauge first
to give an accurate reading, however it is not necessary if you want to
cylinder to cylinder relative comparison. 

So, two key points.

1. Compression Ratio.
2. Mechanical instrument independent of ambient pressure. 

Mike Nakamura
Fall City WA USA
mike_nakamura@domain.elided
91 Spider Veloce
94 164 LS
02 Dakota
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