Date of this Version
Transactions of the ASABE, Vol. 56:3 (2013), pp. 869-879
A John Deere 8295R IVT tractor with a continuously variable transmission (CVT) and a John Deere 8295R PowerShift (PST) tractor with a standard geared transmission (GT) were tested for fuel consumption at three different travel speeds with six different load levels applied per speed. The JD 8295R PST tractor was tested both at full throttle (FT) and shifted up two gears and throttled back (SUTB) to achieve the same travel speed as at full throttle. For each travel speed with each transmission mode, fuel consumption was determined to be linearly related to drawbar power. Linear regression analyses were performed, and the results showed that the tractor with the CVT was more fuel efficient than the tractor with the GT at FT when the power was below 76% to 81% of maximum drawbar power depending on the travel speed. The results also showed that above 37% to 52% of maximum drawbar power, the GT at SUTB was more fuel efficient than the CVT-equipped tractor. As travel speed increased, the percent of maximum power below which the CVT was significantly more fuel efficient than the GT at FT decreased slightly. Likewise, as travel speed increased, the percent of maximum power above which the GT at SUTB was more fuel efficient than the CVT decreased. Some significant differences existed between fuel consumption at different travel speeds within each transmission operating mode. In order to determine differences in fuel consumption between the transmission operating modes and at different travel speeds, testing with at least three loads and at least three travel speeds is recommended. Additional testing is needed on other tractor models, including models from other manufacturers, to determine whether the differences detected in this study pertain to all CVT-equipped tractors or if they are specific to this tractor model and manufacturer.