Effects of Charging System Variability on the Performance and Fuel Economy of a Supercharged Spark-Ignition Engine 2015-01-1286

The paper discusses the effects of various charging system technologies on the performance and fuel consumption of a modern supercharged engine, the Jaguar Land Rover AJ126 3.0 litre V6. The goal of the project was to improve performance and reduce the fuel consumption of the standard engine by researching new technologies around the supercharger. As standard the AJ126 engine uses an Eaton R1320 supercharger with a fixed ratio drive from the crankshaft and no clutch. The project sought to investigate the effect of three novel technologies providing various levels of improvement to the basic specification: a new V1270C V-series supercharger from Eaton with improved low-speed volumetric efficiency (in order to quantify potential improvements in low-speed torque), a clutch to disengage the supercharger completely (to investigate the effect of parasitic losses through churning in the supercharger), and finally a variable-ratio supercharger drive system allowing increased control of air flow to the engine (the Fallbrook NuVinci system, providing the ability to better match supercharger delivery to the instantaneous air mass flow demand of the engine).

The different technologies were first tested individually on a dynamometer in order to compare them to the standard AJ126 configuration. This work package quantified the effect of each technology on full-load performance and also on fuel consumption at discrete speed and torque points used as indicators for regulated fuel economy tests. Time-to-torque was also measured during this phase. The components were then built onto a single test engine and installed in a test vehicle, where in-vehicle performance was evaluated. A switching system permitted the effect of the individual technologies to be evaluated by the driver.

Results are presented for each configuration, and discussion is made regarding where the improvements in fuel economy seen with the different technologies originate from. Finally, some discussion is made regarding the value of variable-speed supercharger drives in compound-charging systems, an area of extreme downsizing that has previously been shown to benefit from greater variability.