FMTV TRANSMISSION FUEL ECONOMY STUDY: EVALUATION OF AMT PERFORMANCE USING EXPERIMENTAL AND ANALYTICAL METHODS

Fuel economy improvements were investigated for the FMTV platform considering alternative transmissions and final drive ratio. An FMTV-M1078 with Caterpillar C7 engine and Allison 3700SP transmission was the target vehicle of this study. Experimental data were collected while vehicle was operated over the FTP72 test cycle. Base vehicle data (vehicle weight, coast-down times, etc.) were collected to provide comparison data for establishing the baseline analytical vehicle model.

Experimental data were processed to determine road load parameters, engine BSFC map, transmission shift schedule and similar for populating the analytical model. Modeling was performed using GT-Drive. The model was analyzed over the same defined drive cycle used to collect the experimental data. Once the model was correlated to the experimental data, updates were made for the variants in transmission and drive-line parameters to be used in the fuel economy study.

The difference between experimental average and the baseline analytical model was approximately 3.1% or 0.2 mi/gal. With a mature base model the transmission variants were introduced. Without changing the final drive ratio the AMT transmissions demonstrated an average 13.4% or ~ 1.0 mi/gal improvement in fuel consumption when compared to an optimized version of the Allison. Changing the final drive ratio provided a more realistic model that takes full advantage of the wider gear range of the AMT transmissions. With the revised final drive ratio the AMT transmissions produced similar results of approximately 22% or 1.75 mi/gal improvement in fuel consumption when compared to an optimized version of the Allison.