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Technical Paper

Test Variability of Emission and Fuel Economy Measurements Using The 1975 Federal Test Procedure

Several sets of repetitive test data using the 1975 Federal Test Procedure ('75 FTP) have been analyzed to establish the variability of each component measured during each phase of the test. The variability characteristics of four different emission control systems have been discussed and compared. The overall variabilities of the '75 FTP composite values have been assessed at ±6% for hydrocarbons and CO, ±3% for NOx, and ±1% for CO2. The extremely repeatable behavior of the CO2 emissions is utilized to calculate the fuel economy during the test. This calculation is discussed and some fuel economy results from repetitive tests are presented.
Technical Paper

Passenger Car Fuel Economy During Non-Urban Driving

The use of fuel economy data from the Federal Test Procedure (FTP) has provided a substantial amount of data on the fuel economy of passenger cars in urban driving conditions. Since the FTP does not represent the type of driving done in rural areas, especially on highways, a driving cycle to assess highway fuel economy was a desirable supplement to the FTP. The new Environmental Protection Agency (EPA) “highway” cycle was constructed from actual speed-versus-time traces generated by an instrumented test car driven over a variety of nonurban roads and highways. This cycle reflects the correct proportion of operation on each of the four major types of nonurban roads and preserves the non-steady-state characteristics of real-world driving. The average speed of the cycle is 48.2 mph and the cycle length is 10.2 miles, close to the average nonurban trip length.