Fuel Consumption Test Procedure - Type II
|Publication Date:||1 October 2020|
This document describes a rigorous-engineering
This recommended practice provides a standardized test procedure to determine the change in a vehicle's fuel consumption by adding, removing, or modifying a vehicle component or system. The procedure utilizes two or more identical medium to heavy-duty single unit or combination vehicles weighing more than 10000 pounds. Vehicles used in the test include an unchanging control vehicle, to provide reference fuel consumption, and test vehicle(s) that are modified during the test process. All vehicles are operated simultaneously and over the identical test circuit during each test run. The test procedure provides a percent difference in fuel consumption between two conditions of a test vehicle(s). A discussion of the data collection and statistical analysis approach are presented in Section 6 and Appendix B.
Limitations and Requirements
The fuel consumed by a moving vehicle is dictated by the aerodynamic and rolling resistive forces acting on the vehicle, with aerodynamic resistance being the dominant force for most vehicles covered by this procedure. In conducting a fuel consumption test, regardless of the technology or system under investigation, it is critically important that unknown and/or uncontrolled variations in aerodynamic and rolling forces are minimized throughout the test process.
a. Minimizing the variation in rolling resistance between vehicles used during a test is accomplished in this procedure by ensuring all vehicles operate at speeds and with tire setup, weight characteristics, and on road surfaces that are within the allowable variations in test criteria described within this document.
b. The minimization of aerodynamic variation is accomplished in this procedure by using vehicles with identical external shapes that are operated on identical drive cycles and by ensuring that vehicle interference effects, air temperature, and wind conditions are within the allowable variations described within this document (see 4.1). Because fuel consumption and data quality are highly sensitive to the presence of wind, it is suggested that testing should be performed in as low a wind speed as possible. The maximum mean wind speed for a run shall be limited (see 4.1). A detailed discussion of wind effects can be found in Appendix A.
The limitations of this procedure are defined below. It is important that all test limitations described below in items "a" through "m" be reviewed and rigorously followed. These limitations are applicable to on-track and on-road testing.
a. Only fuel consumption data obtained from this procedure may be represented as an SAE J1321-Type II test result.
b. Test results generated from any test that does not rigorously follow this method and the test reporting requirements are not intended for public use and dissemination and shall not be represented as an SAE J1321-Type II test result.
c. A test is comprised of a baseline segment and a test segment. Each baseline segment and each test segment are comprised of a minimum of three runs of the control vehicle and test vehicle(s). A single run is a complete circuit of the test route by both the control vehicle and test vehicle(s) where both the control vehicle and test vehicle(s) are operated simultaneously.
d. All test results must be presented in the defined format, with the defined statistical analysis, with vehicle configuration description, and with environmental test information described in this procedure.
e. Test results are valid only for the vehicle configuration, test conditions, and test cycle under which the test was conducted.
f. All vehicles used in the test must have the same external surface contours (preferably the same make, model, and year), tires and wheels (preferably the same type, condition, and mileage), aerodynamic configuration, and powertrain, and are in the same operational and physical condition. Tread must be of the same scalable depth.
g. All vehicles must be operated on identical drive cycle, on identical road surfaces, and within allowable temperature and wind conditions described within this document (see 4.1).
h. All runs are valid, and all test data collected from each run are valid. All test data must be included in the statistical analysis process. Test data may be excluded from the statistical analysis if a documented equipment failure or malfunction or driver error has occurred, or weather condition requirements have been violated. The source of the failure must be recorded and documented in the test report.
i. The test site environmental conditions must be recorded throughout the test. The required environmental data include, but are not limited to, temperature, wind speed, and direction. The data sampling rate must be sufficient to capture any transient environmental effects.
j. The test procedure does not measure or provide aerodynamic data.
k. The general applicability of a valid test result to different environmental factors may be determined when a subsequent valid test result produces a statistically similar value to the initial valid test result under those conditions.
l. If the confidence interval value for a test is greater than or equal to the nominal test value, as determined by the statistical analysis results, it is recommended that additional runs may be conducted to reduce the confidence interval value to less than the nominal test value. For example, if the test result is a nominal value of 3% ± a confidence interval value of 4%, additional runs may reduce the confidence interval to a value less than the nominal value. If additional runs do not show statistically conclusive results, the user must conclude that the change in fuel consumption is either being influenced by variations in the test environment (i.e., weather, driver, etc.) or is less than the test precision.
m. This test procedure requires the use of identical vehicles and therefore it cannot be used to determine the difference in fuel consumption between two different test vehicles (i.e., truck-to-truck comparisons). It is recommended that SAE J1526 test procedure be used to determine the difference in fuel consumption between two different test vehicles.
All users of this document are encouraged to review all sections of this document prior to executing a test program.
This document is structured to service both the novice and the expert user.