Impact of the Future Fuel Economy Targets on Powertrain, Driveline and Vehicle NVH Development 2017-01-1777

The automotive industry continues to develop new technologies aimed at reducing overall vehicle level fuel consumption. Powertrain and driveline related technologies will play a key role in helping OEM’s meet fleet CO₂ reduction targets for 2025 and beyond. Specifically, use of technologies such as downsized engines, idle start-stop systems, aggressive torque converter lock-up schedules, wide-ratio spread transmissions, and electrified propulsion systems are vital towards meeting aggressive fuel economy targets. Judicious combinations of such powertrain and driveline technology packages in conjunction with measures such as the use of low rolling resistance tires and vehicle lightweighting will be required to meet future OEM fleet CO₂ targets. Many of the technologies needed for meeting the fuel economy and CO₂ targets come with unique NVH challenges. In order to ensure customer acceptance of new vehicles, it is imperative that these NVH challenges be understood and solved.

This paper will begin with an introduction of the legislative framework with respect to fuel economy and CO₂ targets for light duty vehicles. Key megatrends of engine, transmission, driveline, and electrified propulsion systems will be examined, following which the NVH behavior of each sub-system will be illustrated. A combination of experimentally measured data and simulations will be used to demonstrate key NVH challenges such as high levels of combustion noise, increased driveline torsional excitation, start-stop refinement, shift quality, and high-frequency whine noise from motors/generators in electrified propulsion systems. Examples of component-level and system-level NVH countermeasures will be discussed. Finally, the use of advanced test and simulation-based methodologies for smooth NVH refinement of future propulsion systems will be illustrated using case study examples.