A little downspeeding saves a lot of money

NASHVILLE, Tenn. — Dana took time at the Technology & Maintenance Council’s annual spring meeting to raise awareness about the benefits – and risks – of engine downspeeding.

Every 100 rpm reduction in engine speed translates to a 1% improvement in fuel economy, meaning there is significant savings to be had by spec’ing downsped powertrains, according to Steve Slesinski, global product planning, commercial vehicle driveline technology with Dana. However, reducing engine speeds and spec’ing faster rear axle ratios also places greater torque on downstream components such as the driveshaft.

Dana's Spicer XFE 75W-90 axle lubricant.
Dana’s Spicer XFE 75W-90 axle lubricant.

Dana promotes a two-pronged approach to protecting against damage that can be caused by the extra torque generated by downsped powertrains: torque-limiting the engine and fortifying the drivetrain.

Slesinski said Dana has come out with products engineered specifically to perform with downsped powertrains. These include the Spicer AdvanTek 40 tandem axle, the SPL 350 driveshaft and the SPL 250 inter-axle shaft. Engine providers can set parameters that torque-limit the engine and reduce the risk of damage caused during low-speed maneuvering, however that won’t protect against high-cycle fatigue, Slesinski said.

While today’s downsped powertrains typically aim for a 1,150 rpm cruise speed, Slesinski said the trend is expected to continue.

“We think rpm is going to continue to go down because of the big benefit you have by improving the efficiency of the engine,” he said, noting cruise speeds of 900 rpm could be attainable in the near future. To this end, Dana is anticipating the need for products that can handle the demands of downspeeding without adding substantial cost and weight to the vehicle.

The company also has taken a leadership role in educating the industry about the benefits of downspeeding, through creation of a new online training module that will go live later this year. The program will help dealers, fleets, service managers and others understand the implications of downspeeding, Slesinski said.

Dana also launched a new drive axle lubricant designed for high-efficiency drivetrains. The all-synthetic Spicer XFE 75W-90 axle lubricant is designed to further reduce operating costs by as much as $730 over a five-year life-cycle. It also qualifies for a 500,000-mile service interval.

Combined with the AdvanTek 40 axle and an engine that is downsped by 200 rpm, a customer can achieve fuel savings of about $9,835 per vehicle over a five-year period based on US$4/gallon diesel prices.


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James Menzies is editor of Today's Trucking. He has been covering the Canadian trucking industry for more than 20 years and holds a CDL. Reach him at james@newcom.ca or follow him on Twitter at @JamesMenzies.

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