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This SAE J2971 Recommended Practice describes a standard naming convention of aerodynamic devices and technologies used to control aerodynamic forces on truck and buses weighing more than 10000 pounds (including trailers).

This SAE J2971 Recommended Practice Truck and Bus Aerodynamic Device Terminology document describes a standard naming convention of aerodynamic devices and technologies used to control aerodynamic forces on truck and buses weighing more than 10,000 pounds (including trailers).

This recommended practice provides minimum requirements for testing components or systems of the type which can be switched from one truck to another with relative ease; i.e., aerodynamic devices, clutch fans, radial tires, and the like. The test utilizes in-service fleet vehicles, operated over representative routes. The relative fuel effectiveness of the component or system under test is determined as a percentage improvement factor. This factor is calculated using the relative fuel usage of like vehicles operating with and without the specific component or system under evaluation. Accuracy capability employing this test technique is either ±1% or ±2%, depending upon the method of fuel measured. (See paragraph 7.4.)

This information report provides background information related to the development of the SAE Recommended Practice that produces relative fuel economy data.

This document describes a rigorous engineering test procedure that utilizes industry-accepted data collection and statistical analysis methods to determine the road load and to estimate the aerodynamic drag area of trucks and buses weighing more than 10000 pounds. The test procedure may be conducted on a test track or on a public road under controlled conditions and supported by extensive data collection and data analysis constraints. The estimated aerodynamic-drag-area result represents a single-speed and single-yaw-angle condition. Test results that do not rigorously follow the method described herein shall not be represented as an SAE J2978 result.

The scope of this recommended practice is sufficiently broad that it can encompass the full range of current heavy duty vehicles, vehicle modifications, and prototype configurations. The test procedure describes methods for examination of the vehicle’s flow field using surface pressures and flow visualization.

The scope of this SAE Recommended Practice is sufficiently broad that it can encompass the full range of current heavy duty vehicles, vehicle modifications, and prototype configurations. The test procedure describes methods for examination of the vehicle’s flow field using surface pressures and flow visualization.

The scope of this SAE Recommended Practice is sufficiently broad that it encompasses the full range of full-scale medium and heavy duty vehicles represented as either full-scale or reduced-scale wind tunnel models. The document provides guidance for wind tunnel testing to support current vehicle characterization, vehicle development, vehicle concept development, and vehicle component development.