As the compression ratio is the ratio of the volume above the piston at
BDC (Bottom Dead Center) and at TDC (Top Dead Center), for two engines
sharing the same basic block (i.e., identical piston diameter and stroke)
the volume of the combustion chamber and the shape of the top of the
piston (crowned vs. flat vs. dished) will affect the compression ratio.
You'd probably find the heads and pistons, at least are different in the
two engines.
Gary McCormick
San Jose, CA
Adam Bradley wrote:
> I know this is a very basic question but I don't understand how
> compression ratio is determined. For example, our R16 engines are 9:1,
> but there was a truck called the "Homer" that also uses the R16 engine
> but is only 8:1 (and has lower hp/torque, also single carb).
>
> I assume this means that on the compression stroke, the air is
> compressed to 1/9th (Roadster) or 1/8th (Homer) its original volume.
> Since both vehicles have the same bore and stroke, what makes the
> compression ratio lower on the truck?
>
> =====
> Adam
> '70 1600 SPL311-28181
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