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Corn+Soybean Digest

Shift Up And Throttle Back

Saving a quarter here or there may not sound like much. But if that's the amount pocketed per acre for every trip over the field, then a $2-3/acre savings will add up.

An extra $3,000 or more at year's end isn't chicken feed, especially with depressed grain and cotton prices. By using a “shift up and throttle back” (SUTB) method of running a tractor, such savings are possible. And wear and tear on equipment are also reduced.

Instead of running full-throttle in a lower gear, shift to a higher gear and throttle back to run at the desired ground speed. The result is the ability to operate an engine more efficiently while maintaining the needed drawbar power, says Steve Searcy, a Texas A&M University ag engineer.

“Engines are more fuel efficient when operated near the manufacturer's rated torque level,” he says. “Shifting to a higher gear and reducing the engine speed causes the engine to produce higher torque, with the associated higher fuel efficiency.”

That can produce a fuel savings of 15-30%, which is a strong cut in costs even when fuel prices are tamed. And who is to say when OPEC oil ministers will reduce production to drive prices up?

Texas grower Lewis Whitaker uses the SUTB method. He likes the reduced grind on his John Deere 4455 as much or more than he likes the fuel savings. “Instead of running full throttle and 2,100 rpm, we will often gear up and run at 1,700 rpm,” says Whitaker, who farms near Claude, TX.

He uses SUTB for planting, cultivating, running a rotary hoe or other jobs performed at a higher speed. “Horsepower is not a big issue for these type jobs,” he says. “If I want to plant at 5½ mph, I select a gear that will let me run at 1,700 and go that speed. There is no need to run with it on the floor when you don't have to.”

Fuel savings are already seen in conservation tillage operations. But for light-to-moderate operations in conventional farming or medium-till, savings could mount quickly with SUTB.

Searcy suggests setting the throttle and gear as usual, begin operating and note your speed. Then SUTB. If the engine speed drops between 170-200 rpm from its original setting, you are in the correct speed-gear combination.

But if the rpm speed doesn't drop, select the next highest gear and throttle back to get the desired ground speed. Use the tachometer to help select the desired ground speed in the new gear. If the new engine speed is less than 70% of the rated speed, then go back to the original settings. But if the new speed is greater than 70% of the rated speed, SUTB is probably in line.

“This 70% figure is typical for most tractors, but growers should check with their operator manuals for more specific information,” Searcy says.

For safety, watch your pyrometer and engine temperature. If your gauges spike suddenly, you're running in too high a gear and should downshift.

Consider Texas A&M's estimated costs of various corn tillage practices, based on diesel at $1.20/gallon, which was common for most 2001 budgets. Overall, the per-acre cost of fuel and lube was projected at about $8.50. But that amount could be whittled down by $2 or more by using SUTB on the light-to-moderate jobs.

Even with 2002 diesel budgeted early on at $1/gallon, the savings will look good on the bottom line.

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