Message text written by "Randall"
>Oh, a few other jokers : CR can vary depending on how much the plug
displaces, most compression gauges don't displace as much (again depending
on which plug you are using). And they aren't all the same, either.
And since compression readings are only to be used as a relative indicator,
the gauges themselves need not be all that accurate. I have two different
gauges, which give results different by 20-30 psi.
<
The volume of the tube ID and the volume of the bourdon tube in the gauge
add to the combustion chamber volume reducing the CR. Different gauges
with different hoses (either length or ID or both) will necessarily give
different readings. The question is: do you, as a gauge manufacturer,
compensate for this effect by adjusting the calibration of the gauge and if
you do, what standard combustion chamber volume do you asume? (Rhetorical
question. You don't compensate because the opens quite the can of worms)
Dave
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