On first generation dmu with bus engines, the engines were not governed (other than having a maximum or red line speed). This is (or was) generally the case for car, bus and truck engines. This arrangement seems well suited to transmission with gears as it allows some variation of power and torque at the same engine speed using different throttle settings. Presumably the same applies to engines on diesel mechanical shunters.
On diesel electric locomotives the engine is governed. A particular throttle setting corresponds to a particular rpm. Within the capacity of the engine to support that load the fuel supply is adjusted to maintain a constant rpm. The same is (or was) true of diesel hydraulic locomotives, a particular throttle setting corresponding to a particular engine speed. In the case of hydraulic transmissions then varying the engine speed was used to vary the input torque to the transmission.
The question is which of these applies to the diesel engines on modern dmu that have a hydro-mechanical transmission? Does a particular throttle notch correspond to a particular engine rpm?
(Or can rpm increase to maximum with the throttle only partially opened, if the load allows this?)
On diesel electric locomotives the engine is governed. A particular throttle setting corresponds to a particular rpm. Within the capacity of the engine to support that load the fuel supply is adjusted to maintain a constant rpm. The same is (or was) true of diesel hydraulic locomotives, a particular throttle setting corresponding to a particular engine speed. In the case of hydraulic transmissions then varying the engine speed was used to vary the input torque to the transmission.
The question is which of these applies to the diesel engines on modern dmu that have a hydro-mechanical transmission? Does a particular throttle notch correspond to a particular engine rpm?
(Or can rpm increase to maximum with the throttle only partially opened, if the load allows this?)
