Biological Systems Engineering, Department of


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A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agricultural and Biological Systems Engineering, Under the Supervision of Professor Michael F. Kocher. Lincoln, Nebraska: December 2010
Copyright 2010 Christopher N. Howard.


A John Deere 8295R IVT tractor with a continuously variable transmission (CVT) and a John Deere 8295R PowerShift (PST) tractor (Waterloo, Iowa) 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 conditions. The three speeds tested corresponded to the maximum speeds achieved in 6th, 8th and 10th gear for the JD 8295R PST tractor at FT. The six load levels corresponded to 30%, 40%, 50%, 60%, 70% and 80% load at maximum power for each selected gear as determined from the unballasted portion of the official OECD Code 2 test (OECD, 2010) for the JD 8295R PST tractor (NTTL, 2010). Linear regression analysis was 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, the percent of maximum power above which the GT at SUTB was more fuel efficient than the CVT decreased as speed increased. Additional testing is needed on other models of tractors from other manufacturers to determine whether the trends found in this study pertain to all CVT equipped tractors or if they are specific to this tractor model and manufacturer.