Abstract
The customers and legislators demand of lower CO2 emissions from passenger cars is accomplished by downsizing combustion engines. Modern combustion engines can be characterized by a reduction of displacement with a high low-end-torque due to supercharging. The size reduction is often combined with a reduction of cylinders. That leads to a torque fluctuation with higher rotational irregularities (RI), which excite the drivetrain and may cause NVH-issues (NVH: Noise, Vibration and Harshness).
In this paper an all-wheel-driven drivetrain with a downsized four-cylinder-diesel-engine is investigated with regards to the acoustic behaviour of the whole passenger car. Due to the different excitation mechanisms (impulsive excitation due to tip-in and periodical excitations due to the combustion) a trade-off in the driveline can be detected. For reducing this conflict a control strategy of existing all-wheel-drive components is suggested.
KEYWORDS – Powertrain, Rotational Irregularities, low-speed-boom, jerk, trade-off