Re: 76 tr6 compression

[Dave Massey <105671.471@compuserve.com>]

Geo writes:
>Can it be as easy as multiplying atmospheric pressure (14.7 psi) times
>compression ratio?  For 7.75 that would be 114 psi.  That sounds low but
so
>does 7.75.
>
>I assume that whatever the formula is it will vary based on your altitude.
>
>Geo Hahn

George,

There's another fly in the ointment and that is the issue of gauge 
pressure vs absolute pressure.  What you say is true about 
atmospheric pressure being 14.7 PSI (14.696 actually but who's 
counting) but the gauge reads in gauge pressure which is short 
hand for the difference between abient (atmospheric) pressure 
and process pressure and the gauge reads zero at atmospheric
pressure.  If you take 14.7 PSI times 7.75 and get 114 PSI this is 
the absolute pressure but your gauge will read 14.7 PSI - less or
99.3 PSI.

Actual readings are quite a bit higher and the only really plausable 
explaination to me is the heating effect that occures when air is 
compressed.

Dave