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Track Road Load Derivations (RLDs) and subsequent load matching on test cell dynamometers has traditionally been conducted using vehicle coastdowns (CDs). Vehicle speed changes during these coastdowns are used to calculate the vehicle mechanical drag forces slowing vehicles when on the road. Track drag force, exerted on a vehicle, can also be quantified by holding a vehicle at a specific steady state speed and measuring the forces required to maintain that speed. This paper focuses on two methods to quantify speed dependent forces which a vehicle must work against when motoring. One method is the traditional coastdown method. The second reference method measures vehicle steady state speed forces necessary to propel the vehicle using both electric vehicle propulsion power flows and dynamometer measured forces. Track CDs require the vehicle to be placed in neutral.

Testing vehicles for emissions and fuel economy has traditionally been conducted with a single-axle chassis dynamometer. The 2006 SAE All Wheel Drive Symposium cited four wheel drive (4WD) and all wheel drive (AWD) sales as climbing from 20% toward 30% of a motor vehicle market share. With an increasing number of four wheel-drive vehicles being introduced to the market place, certification testing for emissions and fuel economy has been changed to allow both two wheel drive and four wheel drive testing [1]. As manufacturers plan to test these vehicles in this mode, test methods need to be developed to allow for these changes. This paper focuses on the tie down methods available for 4WD testing to determine possible effects of test methodologies on a traditional 4WD Vehicle and a hybrid vehicle.

We have established an equation for the density of hydrogen gas that agrees with the current standard to within 0.01 % from 220 to 400 K with pressures up to 45 MPa. The equation is a truncated virial-type equation based on pressure and temperature dependent terms. The density uncertainty for this equation is the same as the current standard and is estimated as 0.2 % (combined uncertainty with a coverage factor of 2). Comparisons are presented with experimental data and with the full 32-term equation of state.

The introduction of hydrogen fuel cell vehicles and their new technology has created the need for development of new fuel economy test procedures and safety procedures during testing. The United States Environmental Protection Agency-National Vehicle Fuels and Emissions Laboratory (U.S. EPA-NVFEL) performed the first hydrogen fuel cell vehicle fuel economy tests in November 2002 and then again in September 2003. It took approximately eight months to comply with the National Fire Protection Association (NFPA) codes related to safe handling of gaseous hydrogen and to design and implement the equipment changes necessary to measure hydrogen fuel economy. This paper will address the facility modifications, data acquisition instrumentation, test procedures and analytical equipment used to accommodate chassis-dynamometer fuel economy testing of a hydrogen-fueled light-duty vehicle.