Doug Miller wrote:
In article , "Terry Coombs" wrote:
Doug Miller wrote:
In article , Don Stauffer
wrote:

Besides, that high compression only comes with full throttle.
???????
Consider the restriction of the throttle plate . You're *NOT* going to get
full cylinder fill , and therefore maximum cylinder pressures at
part-throttle operation .

I guess it depends on exactly what is meant by "high compression". The
compression *ratio* is invariant, determined *only* by the length of the
piston stroke. Compression *pressure* is certainly higher with a full cylinder
fill.
Strange, but somehow I thought that compression ratio was determined by
a ratio of the volume (cylinder volume plus combustion chamber) at BDC
to the volume (cylinder volume plus combustion chamber) at TDC. Piston
cutouts also included of course. My diesel in my truck has similar
stroke length to many gas engines but a whole lot higher ratio, actually
21.1 to 1.

YMMV