February 26, 2017 11:00 PM, EST

NACFE Report Addresses Engine-Driven Accessories

Mike Roeth Mike Roeth by John Sommers II for TT

NASHVILLE, Tenn. — The North American Council for Freight Efficiency released a confidence report on variable engine-driven accessories, some of which have yet to be developed. It was the group’s second report on emerging technologies and 15th overall.

Cooling system water pumps, cooling fans, air compressors, power steering pumps, alternators and air conditioning compressors put a load on the engine, but they do not help propel the vehicle and so are commonly referred to as parasitic loads, NACFE said here Feb. 26 at American Trucking Associations' Technology & Maintenance Council annual meeting.

Because these accessories provide essential vehicle functions, the potential efficiency gains would be accomplished through the implementation of new designs and technology to minimize the energy necessary to provide these functions, according to the NACFE report.

For instance, rather than using an engine to run the compressor when the truck is parked, future air conditioning compressors may be electrically driven. New clutched air compressors also eliminate the robbing of engine power when the air tanks already are at required pressure levels, the report said.

But the report concluded that fuel-economy gains that can be achieved with variable engine-driven accessories for on-highway vehicles are relatively modest.

At the same time, efforts such as downspeeding — which involves slowing the revolutions per minute of the engine at highway speed — cause the accessories to use even less fuel, NACFE Executive Director Michael Roeth said.

In a report from October 2015, NACFE found downspeeding can reduce fuel consumption by 2–3% because it allows the engine to operate at the most fuel-efficient rpm when generating only the minimal horsepower required under cruise conditions.