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 :-)

I pretty much agree, although today's high-speed diesels are doing a lot
better at approchin the constant-enthalpy cycle than they used to,
thanks to being able to divorce the injection profile from crankshaft
position via electronically-controlled injection systems.