In addition, there are sources of friction dependent in
a complexway on the speed of individual moving parts and the
level of lubrication. Also, not all parts of a transmission are
utilised at any given time during vehicle operation. Furthermore,
in hydro-mechanical power-split CVTs, a variable distribution
of transmitted power is present between the hydraulic
and mechanical parts, and this depends on vehicle speed.
Knowledge of the TE of an agricultural tractor permits the
energy losses to be estimated while the tractor is executing
some operations and, to evaluate the goodness of different
tractor/technical solutions. Assessing the transmission efficiency,
given as a set of values related to different speeds and/
or transmitted powers or as a continuous function throughout
the operating range of the vehicle engine, and considering the
construction of any type of transmission (e.g. traditional, fullpowershift,
CVT), is always very difficult both experimentally