Don Stauffer wrote:
Don Stauffer wrote:

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.

Whoops

Before everyone jumps on me, I left off an important qualification.
I
was specifically talking about cars, airplanes and highway trucks.
Large Diesels, (stationary, large ship, etc) do run a different
cycle-
the true Diesel cycle.

However, even the true Diesel cycle of larger engines is not the true

cycle Diesel really wanted. He couldn't develop the true cycle he
wanted (constant enthalpy), and a large Diesel comes somewhat close.
A
high speed (vehicle) engine doesn't even come close with even today's

technology. It is pretty close to an Otto cycle, though still not
exactly. Otto cycle has infinitesmal fraction of cycle for ignition
and
burn, while even a high speed Diesel (and even the SI engine) still
ignites and burns over a finite angle of crank rotation. Still, the
result, as I say is MUCH closer to Otto than the cycle Rudy had
intended. Still makes a good engine, however :-)


You can only get so much speed when you inject the fuel through the
combustion or expansion cycle. High speed diesels get more speed by
injecting more of the fuel early. But an aircraft engine doesn't need
to turn more than 2500 RPM so we should be able to get the benifit of
the longer burn time.