Bryan Martin wrote:
Not so. In the Otto cycle, the fuel and air are introduced to the cylinder
during the intake stroke. In the Diesel cycle only the air is introduce to
the cylinder during the intake stroke, the fuel in injected at the end of
the compression stroke.

in article , Don Stauffer at
wrote on 5/13/05 10:47 AM:


A 4-stroke diesel is still an Otto engine. An Otto cycle engine is one
with four strokes, intake, compression, power, and exhaust. Doesn't
care whether SI or CI.




In terms of the thermodynamics the fuel is immaterial. It is only a
source of heat for raising temp and pressure. The AIR is the true
Carnot working fluid with either a CI or SI engine. In an indicator
diagram of the SI engine, one would be hard pressed to see the
difference even if fuel were shut off during the induction stroke.

The reason a Diesel is not a true (though close) Otto cycle is that in
the true Otto cycle the burning is instantaneous (or at least an
infinitesmal number of degrees of crank rotation or percentage piston
motion.