"Morgans" > wrote in message
news
>
> "Don Stauffer" > wrote
>
> > A two-stroke is more complicated, because it still
> > has (existing, contemporary ones, do anyway) four seperate functions of
> > intake, compression, combustion and exhaust, but have to do it in two
> > strokes.
>
> And some of the operations are happening simultaneously.

There is one very efficient 2-stroke variant that does have separate and
distinct intake, compression, combustion and exhaust functions - the
opposed-piston 2-stroke diesel with the pistons driven by cams, not
crankshafts.

As the pistons move apart (power), the exhaust port is uncovered first by
one piston (exhaust) and then the intake is opened by the other piston so
high pressure air from the supercharger can scavenge the last bits of
exhaust gas from the space between the pistons. After the cylinder is
scavenged, the first piston closes the exhaust port leaving the intake port
open so the supercharger can charge the cylinder with air (intake). Then
both pistons move together closing the intake port (compression). Fuel is
injected directly into the space between the pistons which forms a spherical
combustion chamber (ignition). The cams are designed to optimize the timing
and duration of the port openings as well as contour the compression and
power strokes.

This design makes extreme demands on metallurgy and lubricants so is just
now becoming practical.

Bill Daniels