Steve wrote:
Sport Pilot wrote:


Diesel fuel is not conducive to high speed running. Nor is a long
injection period through much of the expansion phase. Yes you can
boost the turbocharger and the other things, but an Otto cycle
engine
will respond with even higher speeds. Parts failure from speed is
not
a problem with diesel engines, the rotating parts have to be bigger
than an otto engine because of the higher compression, yet the otto
engine will turn higer RPM's with smaller parts.



All of the above is true in the common practice of diesel design, but

none of it is necessarily true. There is nothing FUNDAMENTAL that
limits
a diesel to low-RPM designs only. One can build a screaming high-RPM
diesel with light-weight rotating parts, but one would have to ask
"why?" Gasoline engines are made high-revving in order to increase
power
output from a small package, but diesels can develop a lot more
low-RPM
torque through high boost because they don't detonate when "lugged,"
so
there's no NEED to make them scream. If you need more power, don't
spin
them faster, just boost them harder. High RPM is an aggravation, not
an
advantage (no matter what Honda VTEC drivers think...).


Actually diesels don't really deliver that much torque at similar
speeds. Ok they do but only because the valving is timed for the
slower speeds. Many gasoline tractor engines will diliver similar
torque, but with a higher fuel consumption due to the lower compression
ratio. Diesel fuel burns slower and will knock when the injection
timing is shortened to allow higher speeds.