Gear Shift Pattern Optimization for Best Fuel Economy, Performance and Emissions
FTP-75 drive cycle does not have a prescribed gear shift pattern and automotive OEM has the flexibility to decide. Conventionally the gear shift pattern was arrived at based on trial and error method typically in 10 to 12 Iterations on chassis dynamometer. It was a time consuming (i.e. ~ 3 to 4 months) and costly process. This approach also led to poor fuel economy (FE) labeling declaration. A simulation procedure needed to be established in such cases to generate a gear shift pattern that gives optimal trade-off amongst conflicting objectives (FE, Performance and Emissions). A simulation tool was developed in MATLAB to generate an optimum gear shift pattern. 3 different SUV/UV models were used as test vehicles in this study. Chassis dyno testing was carried out and data was collected using the base and optimized gear shift patterns. Dyno test results with optimized gear shift pattern showed FE improvement of ~ 4 to 5% while retaining the NOx margin well above engineering targets.