Consumption measurements in (almost) real operation

Real Driving Efficiency difficult to measure

Tractors, as a significant group among off-highway commercial vehicles, make it particularly difficult for fuel and lubricant manufacturers when it comes to proving product benefits under real-life conditions. While the engines of many construction machines are subject to high but relatively continuous loads, the field and grassland work of a typical tractor is dynamic, i.e. the loads change constantly. This means not only constant changes between full and partial load, but also multiple shifts between traction drive, auxiliary drive and hydraulic power units, i.e. the proportions of traction, PTO and hydraulic power vary depending on the work to be done. The sheer number of possible test scenarios makes a set-up for field tests to evaluate the performance of fuels and lubricants very difficult. In addition, there are natural conditions such as soil properties or the characteristics of the crop to be processed, which make reproducible and therefore comparable trials almost impossible. 
 

PowerMix as a measuring method

Tractor tests have a long tradition at the DLG (Deutsche Landwirtschafts-Gesellschaft e. V. - German Agricultural Society) – the efficiency and performance of these machines have been tested for over 100 years. While other test centres around the world still carry out consumption measurements during the separate static determination of tractive power and PTO power, i.e. at constant speed at predefined full and partial load points, the DLG Test Center opened a new chapter in the early 2000s with the introduction of the DLG-PowerMix. The DLG-PowerMix test comprises fourteen load cycles that map the specific fuel consumption of tractors under various loads typical in agriculture. By combining the dynamic components of traction, power take-off and hydraulic work, field and grassland work as well as road transport are simulated under standardised, reproducible conditions. With the commissioning of the DLG PowerMix roller test stand, these neutral consumption measurements under defined conditions that are the same for all suppliers could be improved even further and today represent the platinum standard in terms of tractor tests. Axle loads of up to 30 tonnes (60 tonnes machine weight), axle spacings of 2 to 6 metres, power input or output of up to 700 kW each at the four wheels of the travel drive and at the power take-off (PTO) as well as a further 150 kW possible power requirement at the hydraulic system - and the free combinability of all load possibilities - are the core elements of this fully air-conditioned roller test stand of superlatives. A quick change between different tractors makes it easy to change oil or fuel in parallel to the ongoing measurement operation. This means that nothing stands in the way of a comparative evaluation of different fuel types and lubricant combinations for e.g. engine, transmission, hydraulics and axles under controlled and yet practice-relevant conditions.
 

In the end, it is the values and their communication that count

As a result, the DLG test centre has already been able to prove for several well-known mineral oil companies and other customers that a special additivation of fuels or the use of high-performance lubricants can reduce consumption and wear in the area of off-highway commercial vehicles. The DLG test centre is certified according to ISO 17025 and accredited and designated by renowned bodies such as DAkkS or ZLS. The neutrality of the statements is additionally strengthened by the fact that changes to the test specifications, such as the DLG PowerMix, require the approval of the responsible test commissions, i.e. honorary expert committees from science, consulting and practice. This means that the values determined in the DLG trial can also be used to develop effective advertising claims. In this way, product development and sales benefit equally from performance and consumption values measured at the DLG.