SIDI Hybrid Vehicle Technology

The engine of a hybrid electric vehicle (HEV) is the least efficient component in the powertrain. Thus, designers are trying to improve its efficiency, both as a component and through control of the system. Current lean-burn engines, both compression and spark ignition, have the highest potential efficiency among internal combustion engines, but their emissions that may not meet new, stricter emission regulations.

The HEV powertrain itself may offer ways to overcome the limitations of spark-ignition, direct injection (SIDI) engines and unlock their potential even with current emissions-control technology. The ability to load-level engines with electric power in an HEV can be used to overcome the emissions liabilities of SIDI engines. Because acceleration can be moderated and high-speed, high-load operation avoided, much of the operation that produces the highest emissions can be eliminated, greatly easing the burden of the still-immature lean-NOx control systems.

Toyota D4 SIDI Engine with Instrumentation

We have researched SIDI engines for several years by testing, mapping, and analyzing fuel studies on the Toyota D4 SIDI engine and by investigating the trade-offs between in-cylinder bulk air flow and fuel injector characteristics on emissions and engine efficiency.

We also developed a powerful and flexible engine controller. A RPECS (rapid prototyping engine control system) is being installed on a Quad 4 SIDI research engine built for Argonne at the University of Texas. The RPECS allows independent control of the fuel injection and timing, as well as other key engine parameters. A second RPECS will be installed on a Quad 4 engine to verify results and provide a common research platform for future SIDI HEV investigations. The RPECS will also be used to control other engines to tailor their operation for HEV applications.

Future Plans

We plan to investigate the potential of SIDI applications to HEVs by mapping a SIDI engine using the RPECS; fuel efficiency and transient engine-out and tailpipe HC and NO emissions will be measured. The data will be used in PSAT to estimate the fuel economy of the SIDI engine in HEV applications and to develop appropriate control strategies to minimize emissions while capturing the improved fuel economy potential of this engine technology. We also plan to integrate the SIDI engine in a HEV research powertrain to validate the model results and optimize its performance.