Mechanically Supercharged 2.4L GDI Engine for Improved Fuel Economy and Low Speed Torque Improvement

This paper describes the simulation, design, and testing of a mechanically supercharged 2.4L I-4 gasoline direct injection engine with Miller cycle late intake valve closing and high geometric compression ratio. Engine downspeeding is also achieved through modified transmission gear ratios. A 3.3L naturally-aspirated V6 engine was chosen as the benchmark for comparison. Intended vehicle application is a mid-size passenger car or small/mid-size CUV. The CAE tool GT-Power was used for component selection and air path development. The powertrain simulation model was then exercised to show both improved fuel economy and performance compared to the V6 baseline engine. The design of a bespoke integrated supercharger with magnetic clutch, charge air cooler, and intake manifold was made and procured. A large new software aggregate was ported into an existing production ECU with modified internal circuitry. Volumetric efficiency was calibrated using automated engine mapping techniques and software. Data reduction methods compiled the raw outputs into a point-slope format. A full factorial design of experiments yielded models for the most potent calibration areas. Engine dynamometer results show promising fuel economy improvement under simulated FTP drive cycles. Development for supercharger clutch control and in-vehicle testing is currently in progress.