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Comparison of fuel economy and exhaust emission tests of 4WD vehicles using single-axis chassis dynamometer and dual-axis chassis dynamometer
Abstract:
The demands of application of dual-axis chassis dynamometers (4WD-CHDY) have increased recently due to the improvement of performance of 4WD-CHDY and an increase in the number of 4WD vehicles which are difficult to convert to 2WD. However, there are few evaluations of any differences between fuel economy and exhaust emission levels in the case of 2WD-CHDY with conversion from 4WD to 2WD (2WD-mode) and 4WD-CHDY without conversion to 2WD (4WD-mode).
Fuel economy and exhaust emission tests of 4WD vehicle equipped with a typical 4WD mechanism were performed to investigate any differences between the case of the 2WD-mode and the 4WD-mode. In these tests, we measured ‘work at wheel’ (wheel-work) using wheel torque meters.
A comparison of the 2WD-mode and the 4WD-mode reveals a difference of fuel economy (2WD-mode is 1.5% better than that of 4WD-mode) and wheel-work (2WD-mode is 3.9% less than that of 4WD-mode). However, there are almost no differences of exhaust emission levels.
We found the difference of work of loss at tire (tire-loss-work) between the 2WD-mode and the 4WD-mode affects the difference of fuel economy. Moreover, we found the difference of driving force of each tire affects the difference of the total amount of tire-loss-work between the 2WD-mode and the 4WD-mode.
Such evaluation of these differences is new area of research and there are very few studies using wheel torque meters. Therefore, these results provide very valuable information to assess the future necessity of application of 4WD-CHDY.