maybe for best performance
a 'bore' in an engine
should be something other than straight sided?

ring tension is the main component of engine friction

perhaps the bore should have a taper
smaller diameter at the top where there is high pressure
and larger at the bottom to reduce friction?

vast amount of research has gone into making rings better

a considerable amount of research has gone into coatings for bore walls (NikaSil)

but has anyone ever done research
on the shape of a bore under load
that is the best compromise
for pressure seal
but low friction?

in the last 100 years we have learned that nothing in the entire universe is 'dead straight' ... not even beams of light

if I had to bet
I would put my money
on a bore wall shape
that has some kind of curve to it
as being the best performer