Dan Buettner wrote:
>
> That being said, my Bentley manual quotes 8.5:1 for the compression
> ratio on my TR3 and also quotes 120 psi as the compression pressure.
> If you do the math, those numbers would indicate 96% volumetric
> efficiency based on 14.7 psi atmospheric pressure. (so maybe I'm
> full of it)
In addition to the heating affecting the pressure reading, it's entirely
likely that the VE is higher at cranking speeds than at peak power (for
a 'normal' engine).
The compression gauge you use will also make a difference, as some
project into the plug hole/cylinder less than others (thereby changing
the effective CR).
Just two more reasons why only comparative measurements are meaningful.
Randall
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