MCE-5 VCRi demo engine NVH preliminary analysis

Introducing the VCRi kinematic for IC engines is an efficient solution to decrease their fuel consumption. Such a modification has a significant impact on the design of the moving parts and the short block. Specific designed parts required for the new kinematic imply a modification of some key parameters for the NVH behavior of the engine: modified stiffness, modified moving mass, new load paths, new noise sources. A demo engine, fitted in an existing car with standard engine mounts, showed no significant issue on the engine itself although the coupling between the chassis and the engine could not be fully optimized on such a demo car.
First in this paper, the VCRi kinematic is briefly described, with a focus on the main differences related to the NVH behavior and the parameters listed above. Then, new noise sources introduced by the kinematic are described and the retained solutions to reduce them to an acceptable level are defined. The next topic deals with the impact of the modified mass on the balancing characteristics of the engine. Some theoretical considerations are given. Balancing requirements for a L3 engine are discussed and assessed in the context of the VCRi kinematic. The last part is deals with the speed irregularity at the flywheel, showing that its level is not impacted by the VCRi kinematic at any given load, allowing the use of traditional solutions to manage it.