Hyundai Testing Gasoline-Fueled Diesel Engine

Hyundai Motor Co. plans to begin U.S. road tests next year of an experimental gasoline compression-ignition engine in a fleet of Sonata midsize sedans to determine whether the fuel-saving technology should be put into production.

The prototype Hyundai powerplant is a 1.8-liter four-cylinder engine that produces as much as 180 hp while delivering a 25% improvement in fuel economy compared to a spark-ignited gasoline engine.

Gasoline compression-ignition essentially a diesel engine running on gasoline requires a formidable array of variable controls to deliver good performance over the range of speeds and loads encountered by a typical car.

Hyundai's gas direct compression ignition (GDCI) engine is both supercharged and turbocharged, which raises specific output and allows more control over combustion pressure and temperature. The fuel injectors operate at 100-200 bar, compared with 2,000 bar for a conventional diesel. The engine operates at a compression ratio of 14.8:1.

Developers achieved low-temperature combustion by employing multiple late injection, intake boost and combustion heat from exhaust gas recirculation. They used EGR in light-load conditions to promote auto-ignition, a triple injection scheme at moderate loads to maintain high thermal efficiency and late intake valve closing at high loads to reduce the compression ratio.

The Hyundai engine achieves diesel fuel economy without the higher cost of a diesel engine, the company says. The powerplant also can meet emissions standards without the urea treatment system for exhaust gases required by most U.S. diesel engines.

Hyundai says lower production cost of the GDCI compared to a diesel is the primary advantage. But the company is convinced that gasoline will continue to be the major fuel in North America. The high price of diesel in the U.S. is another factor favoring the new engine.

The prototype GDCI has been tested only on a dynamometer so far. Hyundai continues to study the system's performance in simulated transient road conditions. The engine's flat torque curve should make the engine more compatible with conventional transmissions than is true for park-ignited engines, according to the company.

The Hyundai engine is the result of a multi-partner project funded by a $7.5 million grant from the U.S. Dept. of Energy. The research group includes Delphi, Hyundai America Technical Center, Wisconsin Engine Research Consultants and the University of Wisconsin-Madison.