Getting real about test cycles

Fuel consumption of working machines is strongly influenced by machine specification, working environment, and operator behavior, therefore a mix of several test cycles is necessary.

For wheel loaders, excavators, and similar working machines in construction, agriculture, mining, and forestry, the main customer buying criteria are productivity (i.e., material processed per time unit, commonly expressed in ton/h) and energy efficiency (i.e., material processed per unit of energy, expressed, for example, in ton/L standard diesel fuel). These criteria are frequently required to measure both for internal company purposes (to optimize system design and benchmark against competitors) and external purposes (customers benchmarking competing sales offers, as well as possible future legislation).

Similar to the standardized driving cycles for automobiles, people in the nonroad automotive sector have started to develop standardized working cycles. While in the case of automobiles, fuel consumption is tested applying the same driving cycles used in exhaust emissions testing (such as the New European Driving Cycle or U.S. Federal Test Procedure 75), this cannot be done for working machines. Here, exhaust emissions are not measured while using the vehicle (or in this case, machine) but are instead acquired in an engine test bench, where the engine is subjected to a loading cycle with pre-defined torque/speed values (for example according to the Nonroad Transient Cycle, NRTC, or the static ISO 8178 cycle). These methods for testing emissions are a compromise and therefore not optimal in all possible scenarios. More importantly, they cannot be used to also assess fuel consumption, because both productivity and energy efficiency of a working machine are strongly affected by the machine's power system design (with the engine only being one contributing part out of several), as well as the way the operator uses the machine to perform work.