Dual Mode VCS Variable Compression System - System Integration and Vehicle Requirements 2019-01-0248

Future legislation scenarios as well as stringent CO₂ targets, in particular under real driving conditions, will require the introduction of new and additional powertrain technologies. Beside the increasing electrification of the powertrain, it will be essential to utilize the full potential of the Internal Combustion Engine (ICE). There is clearly a competition of new and different ICE-Technologies [1] including VCR. VCR systems are expected to be introduced to a considerable number of next generation turbocharged Spark Ignited (SI) engines in certain vehicle classes. The implementation of Miller or Atkinson cycles is an essential criterion for increased geometric Compression Ratio (CR). The DUAL MODE Variable Compression System (VCS)^TM enables a 2-stage variation of the connecting rod length and thus of the compression ratio (CR). The concept allows a modular integration into existing engine families without significant modifications of the engine architecture and thus represents a cost-attractive solution. The basic functionality and potential were described in a technical paper which was presented at the SAE WCX 2017 [2], the development of the hydraulic function and oil investigations were presented at the SAE WCX 2018 [3].

This paper describes the engine integration of the Dual Mode VCS-system including the hydraulic control system into a state-of-the-art 2.0L-Turbo Gasoline Direct Injected (TGDI)-Engine for the vehicle boundaries of a midsize Sports Utility Vehicle (SUV).

Switching strategies, as well as the importance of short switching duration under Worldwide Harmonized Light Vehicle Test Procedure (WLTP) as well as Real Driving Emissions (RDE) requirements are discussed.

The applied fail-safe operation and Dual Mode VCS position control and detection will be described.

Finally, the Fuel Consumption (FC) impact of the Dual Mode VCS system is discussed. For the 2.0L-TGDI engine in the actual vehicle class, dependent on the load profile and the specific power and torque requirements a CO₂ reduction between 5% and up to 9% in the WLTP is achievable.