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What is PowerMix?

ENGINES IN PARTIAL LOAD RANGE IN REAL-LIFE OPERATIONS

In real working conditions, engines are operated with differing loads and are seldom fully utilised.

To enable analysis of engine characteristics in the partial load range, five additional PTO measurement points were developed and introduced many years ago in cooperation with the industry and trade magazines. In addition to measurements of the full load and the governor control curves, they have become an obligatory part of power and fuel consumption testing according to the OECD Standard Code. The points represent the operating points as they often occur under true field conditions and enable comparisons of absolute and specific fuel consumption in the partial load range.

DLG POWERMIX – THE “FIELD IN THE LAB”

The next step in fuel consumption measurement over the full operating range under simulated conditions, came with the introduction of the new braking wagon at the DLG Test Centre in 2003. To replicate conditions in the field, tractors are now tested for all three output types. Moreover, the operating states are no longer static, but variable, which means that tests are run with changing loads.

THE POWERMIX CYCLES

The loads of a total of twelve cycles are divided into three groups. The first group is pure draft work, i.e. simulation of ploughing and cultivating. These cycles are run in two versions each, once at “100%”, a high load, and once at “60%”, which is a lower load on the tractor. The second includes PTO work simulating operations with a power harrow and mower. Here there are three load levels, 100%, 70% and 40%. Two further cycles, which put an additional power demand on the tractor's hydraulic system, namely cycles with a manure spreader and baler, are also run.

The manufacturers must adhere to certain specifications for ground speed and PTO speed for the individual PowerMix cycles. During the test, care is taken that only those settings are used that can also be replicated by farmers in the field.
CONCLUSION

The DLG PowerMix has now become a recognised test procedure among manufacturers as well as farmers. It provides a good option for comparing the fuel-efficiency tractors under standardised, simulated field conditions. In addition to the engine properties in the full load range, it also allows better conclusions about real-life fuel consumption to be made.

Source: Excerpts from “DLG PowerMix - the “field in the lab””, Friedrich Uhlig, DLG Test Centre Technology and Farm Inputs, Groß-Umstadt, 20.05.2010, www.dlg.org