Shift Up, Throttle Back to Save Tractor Fuel FARM ENERGY Shift Up, Throttle Back to Save Tractor Fuel Farm Energy PM 2089M Today we would like to share some information about on-farm energy conservation. “Shift up and throttle back to save tractor” (PM 2089M) is available from the ISU Farm Energy Conservation & Efficiency Initiative. This project is brought to you by ISU Extension and sponsored by the Iowa Energy Center. Google us or find us on Twitter at “ISU Farm Energy.” [A friendly reminder to presenters: Please remember to properly attribute this and other content published by Iowa State University Extension.]

FARM ENERGY PM 2089M (USDA Census of Agriculture, 2007) Data from the USDA Census of Agriculture shows the distribution of annual energy costs for Iowa producers. As you can see, diesel and gasoline represent the largest direct energy purchase for Iowa farms each year (fertilizer is considered an indirect energy expense). Conserving fuel with a few simple management techniques can help your bottom line, especially when fuel prices are high. (USDA Census of Agriculture, 2007) PM 2089M

FARM ENERGY Tractor operations, particularly chisel plowing, field cultivating, planting and spraying, require different amounts of drawbar pull depending on the size of the implement and soil conditions. When a tractor is only partially loaded, shifting into a higher gear and pulling back on the throttle to reduce fuel consumption allows the operator to harness the same power output from the engine while saving 10% of fuel or more. PM 2089M

FARM ENERGY The concept of shifting up and reducing the tractor throttle setting is similar to what occurs with truck or automotive transmissions during highway travel. At slower starting speeds when the vehicle is still accelerating, the transmission transmits greater torque from the engine by reducing axle speed in a lower transmission gear. Once greater force is no longer required to accelerate the vehicle as it comes up to speed, engine power is shifted to higher transmission gears and the throttle (foot accelerator) is reduced. PM 2089M

FARM ENERGY Many newer tractors have “infinitely” or “continuously” variable transmissions that automatically select the gear and throttle setting depending on the drawbar load requirements and the travel speed chosen by the operator. These transmissions automatically operate at the most fuel efficient level. New features such as this should be considered to improve overall fuel efficiency if you’re considering replacing an older tractor. In the meantime, shifting up and throttling back can help you get the best performance from your older tractors. PM 2089M

FARM ENERGY Tractor operators with fixed-gear transmissions can still easily take advantage of this fuel economy technique by selecting the appropriate gear. Tractor test data from the University of Nebraska-Lincoln tractor lab show potential for fuel savings at reduced drawbar loads. This data is for a 173-hp tractor which produces maximum drawbar power in 7th gear. On the left, if the tractor continues to use 7th gear when operating at a reduced load of 75% of maximum available drawbar power fuel consumption is 11.6 gal/hr at 2090 engine rpm. If the same load is pulled in 9th gear but with a throttle setting reduced to 1580 engine rpm (to maintain the same travel speed and drawbar power output) only 10.5 gal/hr is consumed – a 10% fuel savings. On the right, the same tractor pulling at 50% of drawbar power uses 10.0 gal/hr when pulling in 7th gear at 2150 engine rpm but only 7.9 gal/hr when pulling in 9th gear at the reduced engine speed of 1620 rpm, a 20% fuel savings. PM 2089M

FARM ENERGY Note, the ”shift up, throttle down” technique is not suitable when using power-take-off (PTO) implements (baler, feed wagon, PTO-powered sprayer, etc). PTO shaft speed is directly related to engine speed. Because the PTO implement requires a standard shaft speed input (1000 or 540 rpm), tractor engine speed can’t be reduced. Instead, engine speed is maintained at a level to produce standard PTO speed. PM 2089M

FARM ENERGY Shifting up and throttling back to save fuel is applicable any time available tractor drawbar power significantly exceeds the power required for implement operation. Common examples include: small field cultivator or disk for secondary tillage or a planter, particularly if the implement size is small for the tractor and field conditions and a larger implement could be substituted. Another example is pull-behind sprayer if pump speed is not dependent on standard PTO speed. PM 2089M

FARM ENERGY PM 2089M Summary: Large tractors are often operated with only a partial load (50 – 75% drawbar pull) Shifting up and throttling down with a partial drawbar load can save 10 – 20% of fuel depending on the tractor, load size and soil conditions Avoid overloading or lugging the engine when engine speed is reduced Note: this technique is NOT suitable for PTO work when PTO shaft speed is maintained by engine speed PM 2089M

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