Driven by worldwide climate change, governments are introducing
more stringent emission regulations with particular focus on fuel
saving for CO₂ emission reduction. Downsizing and weight reduction
are two of the main drivers to achieve these demanding regulations.
Both aspects however might have a strong negative effect on the
overall vehicle NVH behavior.
Weight reduction directly influences NVH due to reduction of
absorption and damping material and due to light-weight design
affecting the dynamic responses of powertrain and vehicle
structures. Engine downsizing however has multiple negative effects
on NVH. Beside higher vibrations and speed irregularities due to
lower cylinder numbers and displacements also reduction of sound
quality is a critical topic that will be handled within this
publication.
The first part of this publication will focus on excitation of
engines with different number of cylinders, an alternative mounting
solution for 3-cylinder engines and an overview on the changes of
sound quality for downsized engines.
In the second part two solutions for vehicles with downsized
engines will be presented. The first vehicle is equipped with a
4-cylinder engine and electrical cylinder. By applying appropriate
NVH measures the same NVH behavior as for the original 4 cylinder
without cylinder deactivation can be achieved. Second example is a
vehicle powered by a turbocharged two-cylinder engine. Using active
noise generation, the unconventional sound characteristic of that
vehicle can be changed to that of a standard 4-cylinder engine in
order to increase sound quality and reduce real-life fuel
consumption by positive effects on driving behavior.
