Browse Publications Technical Papers 2003-01-3202
2003-10-27

Direct Measurement of Powertrain Component Efficiencies for a Light-Duty Vehicle with a CVT Operating Over a Driving Cycle 2003-01-3202

In order to determine the factors that affect fuel economy quantitatively, the power flows through the major powertrain components were measured during operation over transient cycles. The fuel consumption rate and torque and speed of the engine output and axle shafts were measured to assess the power flows in a vehicle with a CVT. The measured power flows were converted to energy loss for each component to get the efficiency. Tests were done at Phase 1 and Phase 3 of the FTP and for two different CVT shift modes. The measured energy distributions were compared with those from the ADVISOR simulation and to results from the PNGV study.
For both the Hot 505 and the Cold 505, and for both shift modes, the major powertrain loss occurs in the engine, including or excluding standby losses. However, the efficiency of the drivetrain/transmission is important because it influences the efficiency of the engine. The CVT allows the engine to operate near its peak efficiency line for much of the cycle. Use of the “sports shift” mode rather than the fuel economy mode decreases the efficiency of the CVT and, thereby, moves the engine operating points away from the peak efficiency line.
Even though ADVISOR uses steady state, fully warmed up maps for the engine and transmission to predict behavior over a transient cycle, it predicts the average efficiencies of the engine and CVT within 2% for the Hot 505. However, it underpredicts the fuel economy by 10%, in part due to lack of a means for accounting for the fuel cut during deceleration. The results are not as good as for the Cold 505, for which the component efficiencies and fuel economy are all overpredicts. The technique used by ADVISOR to account for the starting and warm-up need refinement.

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