Technology Package Optimization for Power, Cost, and Efficiency in a Dedicated Range Extender Engine for Electrified Vehicles

A reemergence of manufacturer interest in range-extended electric vehicles is being driven by increasing diversification of consumer interest in low carbon-intensity technologies in the passenger vehicle and other markets. A major advantage of range-extended electric vehicles is that they curtail consumer vehicle range anxiety while maintaining a lower vehicle cost when compared with battery electric vehicles (BEV). By incorporating a small liquid-fueled internal combustion engine (ICE), the range and “refueling” time of electrified vehicles can be significantly improved while overcoming issues with cost and weight faced by long-range battery packs. Compared to ICEs designed for non-hybrid and mild hybrid vehicles, the ICE in a range-extended electric vehicle has a unique set of requirements focused on compact size, low cost, and efficient operation within a limited engine map. The MAHLE Range Extender (REx) is a dedicated engine design for such applications, prioritizing these attributes in a configurable 0.9 liter, 2-cylinder engine. This paper describes the optimization of the REx engine to meet various customer performance requirements. Dedicated range extender engines such as the REx have significant advantages in size, installation flexibility, and overall system weight when compared to engines of similar brake power. These design features are key enablers for one potential market trend of retrofitting vehicles with BEV powertrain architectures to incorporate an optional range extender ICE. The performance of the REx engine can be tailored for a given mission profile through the incorporation of engine technologies such as exhaust gas recirculation, water injection, Miller cam timing, and pre-chamber ignition. The impact of these various technologies on performance, supported by engine test data, and implications on system cost are discussed. Technology packages are proposed for variants of the REx engine optimized for power, efficiency, and cost.