Advanced Functional Pulse Testing of a Two-Stage VCR-System

Two-stage variable compression ratio (VCR) systems for spark ignited engines offer a CO2 reduction potential of approx. 5%. Due to their modularity, connecting rod based VCR-systems can be integrated into existing engine assembly systems, where engines can be built in parallel with or without such a system, depending on performance and market requirements. In order to comply with the new RDE emission standards with high specific power engine variants, VCR systems enable high load engine operation without fuel enrichment. The interactions between the hydraulic-, mechanical - and oil supply systems of a VCR-system with variable connecting rod length are complex and require a well-developed and adapted layout of all subsystems. This demands the use of tailored measurement and simulation tools during the development and application phases. In this context, Advanced Functional Pulse Testing enables single-parameter analyses of VCR con rods. Examples are the determination of the frequency response under constant load cases or the chance for in-depth sensitivity studies on the impacts of various important operational boundary conditions. Another advantage of this testing method is the optimum accessibility for the application of suitable measurement techniques which reduces cost and time requirements compared to in-engine measurements. The testing results deliver important input variables for the validation of complex coupled simulation models. More importantly, a comprehensive analysis enables deeper system understanding and the identification of critical and limiting operation conditions. In this paper the setup of an Advanced Functional Pulse Test including the development of tailor-made pressure sensors will be described and selected results based on an exemplary measurement data will be shown.