The New Aurobay Medium-power Miller Engine

Aurobay has released a 184-kW Miller engine variant, building on the success of their 145-kW Miller engine released in 2021. This new engine, designed for stoichiometric operation, is combined with a Gen3 mild hybrid system to create an efficient and responsive powertrain. The MP Miller engine features a high mounted turbocharger, Variable Nozzle Turbine geometry, and careful tuning of valve lift profiles, camshaft phaser ranges, and turbocharger matching to achieve balanced scavenging and high power. Notably, it maintains continuous lambda 1 operation without fuel enrichment, achieving a specific lambda 1 power of 93.4 kW/l, one of the highest figures globally. The engine also demonstrates robust performance under degraded conditions and broadly available high brake efficiency, contributing to a reduction of at least 5 g CO2/km on the WLTP cycle. Additionally, the Miller cycle and VNT turbocharger have enabled significant cost reductions through reduced precious metal loading in the catalysts. The article provides a comprehensive overview of the engine's development, highlighting the innovative technologies and strategies employed to achieve these remarkable performance and efficiency gains.